Predicting consonant confusions from acoustic analysis

Adaptive Syllable Training Improves Phoneme Identification in Older Listeners with and without Hearing Loss

Acoustic-phonetic speech training mitigates confusion between consonants and improves phoneme identification in noise. A novel training paradigm addressed two principles of perceptual learning. First, training benefits are often specific to the trained material; therefore, stimulus variability was reduced by training small sets of phonetically similar consonant-vowel-consonant syllables. Second, the training is most efficient at an optimal difficulty level; accordingly, the noise level was adapted to the participant's competency. Fifty-two adults aged between sixty and ninety years with normal hearing or moderate hearing loss participated in five training sessions within two weeks. Training sets of phonetically similar syllables contained voiced and voiceless stop and fricative consonants, as well as voiced nasals and liquids. Listeners identified consonants at the onset or the coda syllable position by matching the syllables with their orthographic equivalent within a closed set of three alternative symbols. The noise level was adjusted in a staircase procedure. Pre-post-training benefits were quantified as increased accuracy and a decrease in the required signal-to-noise ratio (SNR) and analyzed with regard to the stimulus sets and the participant's hearing abilities. The adaptive training was feasible for older adults with various degrees of hearing loss. Normal-hearing listeners performed with high accuracy at lower SNR after the training. Participants with hearing loss improved consonant accuracy but still required a high SNR. Phoneme identification improved for all stimulus sets. However, syllables within a set required noticeably different SNRs. Most significant gains occurred for voiced and voiceless stop and (af)fricative consonants. The training was beneficial for difficult consonants, but the easiest to identify consonants improved most prominently. The training enabled older listeners with different capabilities to train and improve at an individual 'edge of competence'.

Reconsidering commonly used stimuli in speech perception experiments

This paper examines some commonly used stimuli in speech perception experiments and raises questions about their use, or about the interpretations of previous results. The takeaway messages are: 1) the Hillenbrand vowels represent a particular dialect rather than a gold standard, and English vowels contain spectral dynamics that have been largely underappreciated, 2) the /ɑ/ context is very common but not clearly superior as a context for testing consonant perception, 3) /ɑ/ is particularly problematic when testing voice-onset-time perception because it introduces strong confounds in the formant transitions, 4) /dɑ/ is grossly overrepresented in neurophysiological studies and yet is insufficient as a generalized proxy for "speech perception," and 5) digit tests and matrix sentences including the coordinate response measure are systematically insensitive to important patterns in speech perception. Each of these stimulus sets and concepts is described with careful attention to their unique value and also cases where they might be misunderstood or over-interpreted.

Speech Categorization Reveals the Role of Early-Stage Temporal-Coherence Processing in Auditory Scene Analysis

Temporal coherence of sound fluctuations across spectral channels is thought to aid auditory grouping and scene segregation. Although prior studies on the neural bases of temporal-coherence processing focused mostly on cortical contributions, neurophysiological evidence suggests that temporal-coherence-based scene analysis may start as early as the cochlear nucleus (i.e., the first auditory region supporting cross-channel processing over a wide frequency range). Accordingly, we hypothesized that aspects of temporal-coherence processing that could be realized in early auditory areas may shape speech understanding in noise. We then explored whether physiologically plausible computational models could account for results from a behavioral experiment that measured consonant categorization in different masking conditions. We tested whether within-channel masking of target-speech modulations predicted consonant confusions across the different conditions and whether predictions were improved by adding across-channel temporal-coherence processing mirroring the computations known to exist in the cochlear nucleus. Consonant confusions provide a rich characterization of error patterns in speech categorization, and are thus crucial for rigorously testing models of speech perception; however, to the best of our knowledge, they have not been used in prior studies of scene analysis. We find that within-channel modulation masking can reasonably account for category confusions, but that it fails when temporal fine structure cues are unavailable. However, the addition of across-channel temporal-coherence processing significantly improves confusion predictions across all tested conditions. Our results suggest that temporal-coherence processing strongly shapes speech understanding in noise and that physiological computations that exist early along the auditory pathway may contribute to this process.SIGNIFICANCE STATEMENT Temporal coherence of sound fluctuations across distinct frequency channels is thought to be important for auditory scene analysis. Prior studies on the neural bases of temporal-coherence processing focused mostly on cortical contributions, and it was unknown whether speech understanding in noise may be shaped by across-channel processing that exists in earlier auditory areas. Using physiologically plausible computational modeling to predict consonant confusions across different listening conditions, we find that across-channel temporal coherence contributes significantly to scene analysis and speech perception and that such processing may arise in the auditory pathway as early as the brainstem. By virtue of providing a richer characterization of error patterns not obtainable with just intelligibility scores, consonant confusions yield unique insight into scene analysis mechanisms.

Phonological and semantic similarity of misperceived words in babble: Effects of sentence context, age, and hearing loss

This study investigated how age and hearing loss influence the misperceptions made when listening to sentences in babble. Open-set responses to final words in sentences with low and high context were analyzed for younger adults with normal hearing and older adults with normal or impaired hearing. All groups performed similarly in overall accuracy but differed in error type. Misperceptions for all groups were analyzed according to phonological and semantic properties. Comparisons between groups indicated that misperceptions for older adults were more influenced by phonological factors. Furthermore, older adults with hearing loss omitted more responses. Overall, across all groups, results suggest that phonological confusions most explain misperceptions in low context sentences. In high context sentences, the meaningful sentence context appears to provide predictive cues that reduce misperceptions. When misperceptions do occur, responses tend to have greater semantic similarity and lesser phonological similarity to the target, compared to low context sentences. In this way, semantic similarity may index a postdictive process by which ambiguities due to phonological confusions are resolved to conform to the semantic context of the sentence. These patterns demonstrate that context, age, and hearing loss affect the misperceptions, and potential sentence interpretation, made when listening to sentences in babble.

Effect of the Target and Conflicting Frequency and Time Ranges on Consonant Enhancement in Normal-Hearing Listeners

In this paper, the effects of intensifying useful frequency and time regions (target frequency and time ranges) and the removal of detrimental frequency and time regions (conflicting frequency and time ranges) for consonant enhancement were determined. Thirteen normal-hearing (NH) listeners participated in two experiments. In the first experiment, the target and conflicting frequency and time ranges for each consonant were identified under a quiet, dichotic listening condition by analyzing consonant confusion matrices. The target frequency range was defined as the frequency range that provided the highest performance and was decreased 40% from the peak performance from both high-pass filtering (HPF) and low-pass filtering (LPF) schemes. The conflicting frequency range was defined as the frequency range that yielded the peak errors of the most confused consonants and was 20% less than the peak error from both filtering schemes. The target time range was defined as a consonant segment that provided the highest performance and was decreased 40% from that peak performance when the duration of the consonant was systematically truncated from the onset. The conflicting time ranges were defined on the coincided target time range because, if they temporarily coincide, the conflicting frequency ranges would be the most detrimental factor affecting the target frequency ranges. In the second experiment, consonant recognition was binaurally measured in noise under three signal processing conditions: unprocessed, intensified target ranges by a 6-dB gain (target), and combined intensified target and removed conflicting ranges (target-conflicting). The results showed that consonant recognition improved significantly with the target condition but greatly deteriorated with a target-conflicting condition. The target condition helped transmit voicing and manner cues while the target-conflicting condition limited the transmission of these cues. Confusion analyses showed that the effect of the signal processing on consonant improvement was consonant-specific: the unprocessed condition was the best for /da, pa, ma, sa/; the target condition was the best for /ga, fa, va, za, ʒa/; and the target-conflicting condition was the best for /na, ʃa/. Perception of /ba, ta, ka/ was independent of the signal processing. The results suggest that enhancing the target ranges is an efficient way to improve consonant recognition while the removal of conflicting ranges negatively impacts consonant recognition.

Older adult recognition error patterns when listening to interrupted speech and speech in steady-state noise

This study examined sentence recognition errors made by older adults in degraded listening conditions compared to a previous sample of younger adults. We examined speech recognition errors made by older normal-hearing adults who repeated sentences that were corrupted by steady-state noise (SSN) or periodically interrupted by noise to preserve 33%, 50%, or 66% of the sentence. Responses were transcribed and coded for the number and type of keyword errors. Errors increased with decreasing preservation of the sentence. Similar sentence recognition was observed between SSN and the greatest amount of interruption (33%). Errors were predominately at the word level rather than at the phoneme level and consisted of omission or substitution of keywords. Compared to younger listeners, older listeners made more total errors and omitted more whole words when speech was highly degraded. They also made more whole word substitutions when speech was more preserved. In addition, the semantic relatedness of the substitution errors to the sentence context varied according to the distortion condition, with greater context effects in SSN than interruption. Overall, older listeners made errors reflecting poorer speech representations. Error analyses provide a more detailed account of speech recognition by identifying changes in the type of errors made across listening conditions and listener groups.

Listening Effort Is Not the Same as Speech Intelligibility Score

Listening effort is a valuable and important notion to measure because it is among the primary complaints of people with hearing loss. It is tempting and intuitive to accept speech intelligibility scores as a proxy for listening effort, but this link is likely oversimplified and lacks actionable explanatory power. This study was conducted to explain the mechanisms of listening effort that are not captured by intelligibility scores, using sentence-repetition tasks where specific kinds of mistakes were prospectively planned or analyzed retrospectively. Effort measured as changes in pupil size among 20 listeners with normal hearing and 19 listeners with cochlear implants. Experiment 1 demonstrates that mental correction of misperceived words increases effort even when responses are correct. Experiment 2 shows that for incorrect responses, listening effort is not a function of the proportion of words correct but is rather driven by the types of errors, position of errors within a sentence, and the need to resolve ambiguity, reflecting how easily the listener can make sense of a perception. A simple taxonomy of error types is provided that is both intuitive and consistent with data from these two experiments. The diversity of errors in these experiments implies that speech perception tasks can be designed prospectively to elicit the mistakes that are more closely linked with effort. Although mental corrective action and number of mistakes can scale together in many experiments, it is possible to dissociate them to advance toward a more explanatory (rather than correlational) account of listening effort.

Vowel Context Effect on the Perception of Stop Consonants in Malayalam and Its Role in Determining Syllable Frequency

Background and Objectives

The study investigated vowel context effects on the perception of stop consonants in Malayalam. It also probed into the role of vowel context effects in determining the frequency of occurrence of various consonant-vowel (CV) syllables in Malayalam.

Subjects and Methods

The study used a cross-sectional pre-experimental post-test only research design on 30 individuals with normal hearing, who were native speakers of Malayalam. The stimuli included three stop consonants, each spoken in three different vowel contexts. The resultant nine syllables were presented in original form and five gating conditions. The consonant recognition in different vowel contexts of the participants was assessed. The frequency of occurrence of the nine target syllables in the spoken corpus of Malayalam was also systematically derived.

Results

The consonant recognition score was better in the /u/ vowel context compared with /i/ and /a/ contexts. The frequency of occurrence of the target syllables derived from the spoken corpus of Malayalam showed that the three stop consonants occurred more frequently with the vowel /a/ compared with /u/ and /i/.

Conclusions

The findings show a definite vowel context effect on the perception of the Malayalam stop consonants. This context effect observed is different from that in other languages. Stop consonants are perceived better in the context of /u/ compared with the /a/ and /i/ contexts. Furthermore, the vowel context effects do not appear to determine the frequency of occurrence of different CV syllables in Malayalam.

Perceptual Benefits of Extended Bandwidth Hearing Aids With Children: A Within-Subject Design Using Clinically Available Hearing Aids

Purpose The aim of the study was to investigate the achieved audibility with clinically available, modern, high-end, behind-the-ear hearing aids fitted using the Desired Sensation Level v5.0 child prescription for a clinical sample of children with hearing impairment and the effect of the extended bandwidth provided by the hearing aids on several outcome measures. Method The achieved audibility was measured using the maximum audible output frequency method. Twenty-eight children (7-17 years old) with mild to severe hearing losses completed this study. Two hearing aid conditions were fitted for each participant: an extended bandwidth condition, which was fitted to targets as closely as possible, and a restricted bandwidth condition, for which aided output was restricted above 4.5 kHz. Consonant discrimination in noise, subjective preference, aided loudness growth, and preferred listening levels were evaluated in both conditions. Results The extended bandwidth hearing aid fittings provided speech audibility above 4.5 kHz for all children, with an average maximum audible output frequency of 7376 Hz (SD = 1669 Hz). When compared to a restricted bandwidth, the extended bandwidth condition led to an improvement of 5.4% for consonant discrimination in noise scores, mostly attributable to /s/, /z/, and /t/ phoneme perception. Aided loudness results and preferred listening levels were not significantly different across bandwidth conditions; however, 65% of the children indicated a subjective preference for the extended bandwidth. Conclusion The study suggests that providing the full bandwidth available, with modern, behind-the-ear hearing aids, leads to improved audibility, when compared to restricted bandwidth hearing aids, and that it leads to beneficial outcomes for children who use hearing aids, fitted to the Desired Sensation Level v5.0 child prescription, without causing significant increases in their loudness perception.

Speech recognition, loudness, and preference with extended bandwidth hearing aids for adult hearing aid users

Objective: In contrast to the past, some current hearing aids can provide gain for frequencies above 4-5 kHz. This study assessed the effect of wider bandwidth on outcome measures using hearing aids fitted with the DSL v5.0 prescription.Design: There were two conditions: an extended bandwidth condition, for which the maximum available bandwidth was provided, and a restricted bandwidth condition, in which gain was reduced for frequencies above 4.5 kHz. Outcome measures were assessed in both conditions.Study sample: Twenty-four participants with mild-to-moderately-severe sensorineural high-frequency sloping hearing loss.Results: Providing extended bandwidth resulted in maximum audible output frequency values of 7.5 kHz on average for an input level of 65 dB SPL. An improvement in consonant discrimination scores (4.1%), attributable to better perception of /s/, /z/, and /t/ phonemes, was found in the extended bandwidth condition, but no significant change in loudness perception or preferred listening levels was found. Most listeners (79%) had either no preference (33%) or some preference for the extended bandwidth condition (46%).Conclusions: The results suggest that providing the maximum bandwidth available with modern hearing aids fitted with DSL v5.0, using targets from 0.25 to 8 kHz, can be beneficial for the tested population.

Systematic Review of Auditory Training in Pediatric Cochlear Implant Recipients

Objective The purpose of this systematic review is to evaluate the published research in auditory training (AT) for pediatric cochlear implant (CI) recipients. This review investigates whether AT in children with CIs leads to improvements in speech and language development, cognition, and/or quality of life and whether improvements, if any, remain over time post AT intervention. Method A systematic search of 7 databases identified 96 review articles published up until January 2017, 9 of which met the inclusion criteria. Data were extracted and independently assessed for risk of bias and quality of study against a PICOS (participants, intervention, control, outcomes, and study) framework. Results All studies reported improvements in trained AT tasks, including speech discrimination/identification and working memory. Retention of improvements over time was found whenever it was assessed. Transfer of learning was measured in 4 of 6 studies, which assessed generalization. Quality of life was not assessed. Overall, evidence for the included studies was deemed to be of low quality. Conclusion Benefits of AT were illustrated through the improvement in trained tasks, and this was observed in all reviewed studies. Transfer of improvement to other domains and also retention of benefits post AT were evident when assessed, although rarely done. However, higher quality evidence to further examine outcomes of AT in pediatric CI recipients is needed.

Effects of vowel context and discriminability on band independence in nonsense syllable recognition

The Speech Intelligibility Index algorithm [(1997). ANSI S3.5-1997] models cues in disjoint frequency bands for consonants and vowels as additive, independent contributions to intelligibility. Data from other studies examining only consonants in single-vowel nonsense stimuli exhibit synergetic and redundant band contributions that challenge the band independence assumption. The present study tested the hypotheses that (a) band independence is present for multi-vowel stimuli, and (b) dependent band contributions are artifacts of confounding stimulus administration and testing methods. Data were measured in two experiments in which subjects identified filtered nonsense consonant-vowel-consonant syllables using a variety of randomly selected vowels. The measured data were used in simulations that further characterized the range of subject responses. Results of testing and simulation suggest that, where present, band independence is fostered by low broadband error, high vowel diversity, and high vowel discriminability. Synergistic band contributions were observed for confusable vowels that were most susceptible to filtering; redundant contributions were observed for the least susceptible vowels. Implications for intelligibility prediction and enhancement are discussed.

Forward and Backward Masking of Consonants in School-Age Children and Adults

PURPOSE

This experiment sought to determine whether children's increased susceptibility to nonsimultaneous masking, particularly backward masking, is evident for speech stimuli.

METHOD

Five- to 9-year-olds and adults with normal hearing heard nonsense consonant-vowel-consonant targets. In Experiments 1 and 2, those targets were presented between two 250-ms segments of 70-dB-SPL speech-shaped noise, at either -30 dB signal-to-noise ratio (Experiment 1) or at the listener's word recognition threshold (Experiment 2). In Experiment 3, the target was presented in steady speech-shaped noise at listener threshold. For all experiments, percent correct was estimated for initial and final consonants.

RESULTS

In the nonsimultaneous noise conditions, child-adult differences were larger for the final consonant than the initial consonant whether listeners were tested at -30 dB signal-to-noise ratio (Experiment 1) or at their individual word recognition threshold (Experiment 2). Children were not particularly susceptible to backward masking relative to adults when tested in a steady masker (Experiment 3).

CONCLUSIONS

Child-adult differences were greater for backward than forward masking for speech in a nonsimultaneous noise masker, as observed in previous psychophysical studies using tonal stimuli. Children's greater susceptibility to nonsimultaneous masking, and backward masking in particular, could play a role in their limited ability to benefit from masker envelope modulation when recognizing masked speech.

Recognition of Spanish consonants in 8-talker babble by children with cochlear implants, and by children and adults with normal hearing

This paper presents the results of closed-set recognition task for 80 Spanish consonant-vowel sounds in 8-talker babble. Three groups of subjects participated in the study: a group of children using cochlear implants (CIs; age range: 7-13), an age-matched group of children with normal hearing (NH), and a group of adults with NH. The speech-to-noise ratios at which the participants recognized 33% of the target consonants were +7.8 dB, -3 dB, and -6 dB, respectively. In order to clarify the qualitative differences between the groups, groups were matched for the percentage of recognized syllables. As compared with the two groups with NH, the children with CIs: (1) produced few "I do not know" responses; (2) frequently selected the voiced stops (i.e., /b, d, ɡ/) and the most energetic consonants (i.e., /l, r, ʝ, s, ʧ/); (3) showed no vowel context effects; and (4) had a robust voicing bias. As compared with the adults with NH, both groups of children showed a fronting bias in place of articulation errors. The factors underlying these error patterns are discussed.

Effect of Vowel Context on the Recognition of Initial Consonants in Kannada

Background and Objectives

The present study was carried out to investigate the effect of vowel context on the recognition of Kannada consonants in quiet for young adults.

Subjects and Methods

A total of 17 young adults with normal hearing in both ears participated in the study. The stimuli included consonant-vowel syllables, spoken by 12 native speakers of Kannada. Consonant recognition task was carried out as a closed-set (fourteen-alternative forced-choice).

Results

The present study showed an effect of vowel context on the perception of consonants. Maximum consonant recognition score was obtained in the /o/ vowel context, followed by the /a/ and /u/ vowel contexts, and then the /e/ context. Poorest consonant recognition score was obtained in the vowel context /i/.

Conclusions

Vowel context has an effect on the recognition of Kannada consonants, and the vowel effect was unique for Kannada consonants.

Analysis of Spanish consonant recognition in 8-talker babble

This paper presents the results of a closed-set recognition task for 80 Spanish consonant-vowel sounds (16 C × 5 V, spoken by 2 talkers) in 8-talker babble (-6, -2, +2 dB). A ranking of resistance to noise was obtained using the signal detection d' measure, and confusion patterns were analyzed using a graphical method (confusion graphs). The resulting ranking indicated the existence of three resistance groups: (1) high resistance: /ʧ, s, ʝ/; (2) mid resistance: /r, l, m, n/; and (3) low resistance: /t, θ, x, ɡ, b, d, k, f, p/. Confusions involved mostly place of articulation and voicing errors, and occurred especially among consonants in the same resistance group. Three perceptual confusion groups were identified: the three low-energy fricatives (i.e., /f, θ, x/), the six stops (i.e., /p, t, k, b, d, ɡ/), and three consonants with clear formant structure (i.e., /m, n, l/). The factors underlying consonant resistance and confusion patterns are discussed. The results are compared with data from other languages.

Interventions to improve hearing aid use in adult auditory rehabilitation

BACKGROUND

Acquired adult-onset hearing loss is a common long-term condition for which the most common intervention is hearing aid fitting. However, up to 40% of people fitted with a hearing aid either fail to use it or may not gain optimal benefit from it. This is an update of a review first published in The Cochrane Library in 2014.

OBJECTIVES

To assess the long-term effectiveness of interventions to promote the use of hearing aids in adults with acquired hearing loss fitted with at least one hearing aid.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Trials Register; Central Register of Controlled Trials (CENTRAL 2016, Issue 5); PubMed; EMBASE; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 13 June 2016.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of interventions designed to improve or promote hearing aid use in adults with acquired hearing loss compared with usual care or another intervention. We excluded interventions that compared hearing aid technology. We classified interventions according to the 'chronic care model' (CCM). The primary outcomes were hearing aid use (measured as adherence or daily hours of use) and adverse effects (inappropriate advice or clinical practice, or patient complaints). Secondary patient-reported outcomes included quality of life, hearing handicap, hearing aid benefit and communication. Outcomes were measured over the short (</= 12 weeks), medium (> 12 to < 52 weeks) and long term (one year plus).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 37 studies involving a total of 4129 participants. Risk of bias across the included studies was variable. We judged the GRADE quality of evidence to be very low or low for the primary outcomes where data were available.The majority of participants were over 65 years of age with mild to moderate adult-onset hearing loss. There was a mix of new and experienced hearing aid users. Six of the studies (287 participants) assessed long-term outcomes.All 37 studies tested interventions that could be classified using the CCM as self-management support (ways to help someone to manage their hearing loss and hearing aid(s) better by giving information, practice and experience at listening/communicating or by asking people to practise tasks at home) and/or delivery system design interventions (just changing how the service was delivered). Self-management support interventions We found no studies that investigated the effect of these interventions on adherence, adverse effects or hearing aid benefit. Two studies reported daily hours of hearing aid use but we were unable to combine these in a meta-analysis. There was no evidence of a statistically significant effect on quality of life over the medium term. Self-management support reduced short- to medium-term hearing handicap (two studies, 87 participants; mean difference (MD) -12.80, 95% confidence interval (CI) -23.11 to -2.48 (0 to 100 scale)) and increased the use of verbal communication strategies in the short to medium term (one study, 52 participants; MD 0.72, 95% CI 0.21 to 1.23 (0 to 5 scale)). The clinical significance of these statistical findings is uncertain. It is likely that the outcomes were clinically significant for some, but not all, participants. Our confidence in the quality of this evidence was very low. No self-management support studies reported long-term outcomes. Delivery system design interventionsThese interventions did not significantly affect adherence or daily hours of hearing aid use in the short to medium term, or adverse effects in the long term. We found no studies that investigated the effect of these interventions on quality of life. There was no evidence of a statistically or clinically significant effect on hearing handicap, hearing aid benefit or the use of verbal communication strategies in the short to medium term. Our confidence in the quality of this evidence was low or very low. Long-term outcome measurement was rare. Combined self-management support/delivery system design interventionsOne combined intervention showed evidence of a statistically significant effect on adherence in the short term (one study, 167 participants, risk ratio (RR) 1.06, 95% CI 1.00 to 1.12). However, there was no evidence of a statistically or clinically significant effect on daily hours of hearing aid use over the long term, or the short to medium term. No studies of this type investigated adverse effects. There was no evidence of an effect on quality of life over the long term, or short to medium term. These combined interventions reduced hearing handicap in the short to medium term (15 studies, 728 participants; standardised mean difference (SMD) -0.26, 95% CI -0.48 to -0.04). This represents a small-moderate effect size but there is no evidence of a statistically significant effect over the long term. There was evidence of a statistically, but not clinically, significant effect on long-term hearing aid benefit (two studies, 69 participants, MD 0.30, 95% CI 0.02 to 0.58 (1 to 5 scale)), but no evidence of an effect over the short to medium term. There was evidence of a statistically, but not clinically, significant effect on the use of verbal communication strategies in the short term (four studies, 223 participants, MD 0.45, 95% CI 0.15 to 0.74 (0 to 5 scale)), but not the long term. Our confidence in the quality of this evidence was low or very low.We found no studies that assessed the effect of other CCM interventions (decision support, the clinical information system, community resources or health system changes).

AUTHORS' CONCLUSIONS

There is some low to very low quality evidence to support the use of self-management support and complex interventions combining self-management support and delivery system design in adult auditory rehabilitation. However, effect sizes are small. The range of interventions that have been tested is relatively limited. Future research should prioritise: long-term outcome assessment; development of a core outcome set for adult auditory rehabilitation; and study designs and outcome measures that are powered to detect incremental effects of rehabilitative healthcare system changes.

Objective measures of perceptual quality for predicting speech intelligibility in sensorineural hearing loss

An objective method to predict speech intelligibility in sensorineural hearing loss of different types and increasing degrees of severity is proposed and validated with experimental data. The novel approach is based on the combined use of acoustic simulations of impaired perception and objective measures of perceptual speech quality (PESQ). Acoustic simulations were obtained after degradation of the original, non distorted, speech waveforms by spectral smearing, expansive nonlinearity, and level scaling. PESQ was used to measure perceptual quality of the acoustic simulations obtained by varying the degree of the simulated hearing loss. A logistic function was applied to transform PESQ scores into predicted intelligibility scores. A set of CV and VC syllables in /a/, /u/, and /i/ contexts was used as reference test material. The method was validated with subjective measures of intelligibility of the degraded speech obtained in a group of 10 normal hearing subjects. Overall, prediction of experimental speech intelligibility through the transformed PESQ measures was good (R(2)=0.7; RMSE=0.08) revealing that the proposed approach could be a valuable aid in real clinical applications.

Effects of low-pass filtering on the perception of word-final plurality markers in children and adults with normal hearing

PURPOSE

The purpose of this study was to evaluate the effect of low-pass filtering on the detection of word-final /s/ and /z/ for children and adults with normal hearing.

METHOD

Stimuli were nouns from the University of Western Ontario Plurals Test (Glista & Scollie, 2012), low-pass filtered with 5 different cutoff frequencies: 8000 Hz, 5000 Hz, 4000 Hz, 3000 Hz, and 2000 Hz. Listeners were children (age range = 7-13 years) and adults with normal hearing. The task was a 2-alternative forced-choice task with a picture-pointing response.

RESULTS

Performance was worse for lower than for higher low-pass filter cutoff frequencies, but the effect of low-pass filtering was similar for children and adults. Nearly all listeners achieved 100% correct performance when stimuli were low-pass filtered with cutoff frequencies of 8000 Hz or 5000 Hz. Performance remained well above chance even for the most severe filtering condition (2000 Hz). Restricting high-frequency audibility influenced performance for plural items to a greater extent than for singular items.

CONCLUSION

The results indicate that children and adults with normal hearing can use acoustic information below the spectral range of frication noise typically associated with /s/ and /z/ to discriminate between singular and plural forms of nouns in the context of the University of Western Ontario Plurals Test.

Interventions to improve hearing aid use in adult auditory rehabilitation

BACKGROUND

Acquired adult-onset hearing loss is a common long-term condition for which the most common intervention is hearing aid fitting. However, up to 40% of people fitted with a hearing aid either fail to use it or may not gain optimal benefit from it.

OBJECTIVES

To assess the long-term effectiveness of interventions to promote the use of hearing aids in adults with acquired hearing loss fitted with at least one hearing aid.

SEARCH METHODS

We searched the Cochrane ENT Disorders Group Trials Register; CENTRAL; PubMed; EMBASE; CINAHL; Web of Science; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 6 November 2013.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of interventions designed to improve or promote hearing aid use in adults with acquired hearing loss compared with usual care or another intervention. We excluded interventions that compared hearing aid technology. We classified interventions according to the 'chronic care model' (CCM). The primary outcomes were hearing aid use (measured as adherence or daily hours of use) and adverse effects (inappropriate advice or clinical practice, or patient complaints). Secondary patient-reported outcomes included quality of life, hearing handicap, hearing aid benefit and communication. Outcomes were measured over the short (</= 12 weeks), medium (> 12 to < 52 weeks) and long term (one year plus).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included 32 studies involving a total of 2072 participants. The risk of bias across the included studies was variable. We judged the GRADE quality of evidence to be very low or low for the primary outcomes where data were available.The majority of participants were over 65 years of age with mild to moderate adult-onset hearing loss. There was a mix of new and experienced hearing aid users. Six of the studies (1018 participants) were conducted in a military veteran population. Six of the studies (287 participants) assessed long-term outcomes.All 32 studies tested interventions that could be classified as self management support (ways to help someone to manage their hearing loss and hearing aid(s) better by giving information, practice and experience at listening/communicating or by asking people to practise tasks at home) and/or delivery system design interventions (just changing how the service was delivered) according to the CCM. Self management support interventions We found no studies that investigated the effect of these interventions on adherence, adverse effects or hearing aid benefit. Two studies reported daily hours of hearing aid use but we were unable to combine these in a meta-analysis. There was no evidence of a statistically significant effect on quality of life over the medium term. Self management support reduced short- to medium-term hearing handicap (two studies, 87 participants; mean difference (MD) -12.80, 95% confidence interval (CI) -23.11 to -2.48 (0 to 100 scale)) and increased the use of verbal communication strategies in the short to medium term (one study, 52 participants; MD 0.72, 95% CI 0.21 to 1.23 (0 to 5 scale)). The clinical significance of these statistical findings is uncertain but it is likely that the outcomes were clinically significant for some, but not all, participants. Our confidence in the quality of this evidence was very low. No self management support studies reported long-term outcomes. Delivery system design interventions These interventions did not significantly affect adherence or daily hours of hearing aid use in the short to medium term, or adverse effects in the long term. We found no studies that investigated the effect of these interventions on quality of life. There was no evidence of a statistically or clinically significant effect on hearing handicap, hearing aid benefit or the use of verbal communication strategies in the short to medium term. Our confidence in the quality of this evidence was low or very low. Long-term outcome measurement was rare. Combined self management support/delivery system design interventions We found no studies that investigated the effect of complex interventions combining components of self management support and delivery system design on adherence or adverse effects. There was no evidence of a statistically or clinically significant effect on daily hours of hearing aid use over the long term, or the short to medium term. Similarly, there was no evidence of an effect on quality of life over the long term, or short to medium term. These combined interventions reduced hearing handicap in the short to medium term (13 studies, 485 participants, standardised mean difference (SMD) -0.27, 95% CI -0.49 to -0.06). This represents a small-moderate effect size but there is no evidence of a statistically significant effect over the long term. There was evidence of a statistically, but not clinically, significant effect on long-term hearing aid benefit (two studies, 69 participants, MD 0.30, 95% CI 0.02 to 0.58 (1 to 5 scale)), but no evidence of effect over the short to medium term. There was evidence of a statistically, but not clinically, significant effect on the use of verbal communication strategies in the short term (four studies, 223 participants, MD 0.45, 95% CI 0.15 to 0.74 (0 to 5 scale)), but not the long term. Our confidence in the quality of this evidence was low or very low.We found no studies that assessed the effect of other CCM interventions (decision support, the clinical information system, community resources or health system changes).

AUTHORS' CONCLUSIONS

There is some low to very low quality evidence to support the use of self management support and complex interventions combining self management support and delivery system design in adult auditory rehabilitation. However, effect sizes are small and the range of interventions that have been tested is relatively limited. Priorities for future research should be assessment of long-term outcome a year or more after the intervention, development of a core outcome set for adult auditory rehabilitation and development of study designs and outcome measures that are powered to detect incremental effects of rehabilitative healthcare system changes over and above the provision of a hearing aid.

Children's identification of consonants in a speech-shaped noise or a two-talker masker

PURPOSE

To evaluate child-adult differences for consonant identification in a noise or a 2-talker masker. Error patterns were compared across age and masker type to test the hypothesis that errors with the noise masker reflect limitations in the peripheral encoding of speech, whereas errors with the 2-talker masker reflect target-masker confusions within the central auditory system.

METHOD

A repeated-measures design compared the performance of children (5-13 years) and adults in continuous speech-shaped noise or a 2-talker masker. Consonants were identified from a closed set of 12 using a picture-pointing response.

RESULTS

In speech-shaped noise, children under age 10 years performed more poorly than adults, but performance was adultlike for 11- to 13-year-olds. In the 2-talker masker, significant child-adult differences were observed in even the oldest group of children. Systematic clusters of consonant errors were observed for children in the noise masker and for adults in both maskers, but not for children in the 2-talker masker.

CONCLUSIONS

These results suggest a more prolonged time course of development for consonant identification in a 2-talker masker than in a noise masker. Differences in error patterns between the maskers support the hypothesis that errors with the 2-talker masker reflect failures of sound segregation.

Roles of voice onset time and F0 in stop consonant voicing perception: effects of masking noise and low-pass filtering

PURPOSE

The contributions of voice onset time (VOT) and fundamental frequency (F0) were evaluated for the perception of voicing in syllable-initial stop consonants in words that were low-pass filtered and/or masked by speech-shaped noise. It was expected that listeners would rely less on VOT and more on F0 in these degraded conditions.

METHOD

Twenty young listeners with normal hearing identified modified natural speech tokens that varied by VOT and F0 in several conditions of low-pass filtering and masking noise. Stimuli included /b/-/p/ and /d/-/t/ continua that were presented in separate blocks. Identification results were modeled using mixed-effects logistic regression.

RESULTS

When speech was filtered and/or masked by noise, listeners' voicing perceptions were driven less by VOT and more by F0. Speech-shaped masking noise exerted greater effects on the /b/-/p/ contrast, while low-pass filtering exerted greater effects on the /d/-/t/ contrast, consistent with the acoustics of these contrasts.

CONCLUSION

Listeners can adjust their use of acoustic-phonetic cues in a dynamic way that is appropriate for challenging listening conditions; cues that are less influential in ideal conditions can gain priority in challenging conditions.

Efficacy of individual computer-based auditory training for people with hearing loss: a systematic review of the evidence

Background

Auditory training involves active listening to auditory stimuli and aims to improve performance in auditory tasks. As such, auditory training is a potential intervention for the management of people with hearing loss.

Objective

This systematic review (PROSPERO 2011: CRD42011001406) evaluated the published evidence-base for the efficacy of individual computer-based auditory training to improve speech intelligibility, cognition and communication abilities in adults with hearing loss, with or without hearing aids or cochlear implants.

Methods

A systematic search of eight databases and key journals identified 229 articles published since 1996, 13 of which met the inclusion criteria. Data were independently extracted and reviewed by the two authors. Study quality was assessed using ten pre-defined scientific and intervention-specific measures.

Results

Auditory training resulted in improved performance for trained tasks in 9/10 articles that reported on-task outcomes. Although significant generalisation of learning was shown to untrained measures of speech intelligibility (11/13 articles), cognition (1/1 articles) and self-reported hearing abilities (1/2 articles), improvements were small and not robust. Where reported, compliance with computer-based auditory training was high, and retention of learning was shown at post-training follow-ups. Published evidence was of very-low to moderate study quality.

Conclusions

Our findings demonstrate that published evidence for the efficacy of individual computer-based auditory training for adults with hearing loss is not robust and therefore cannot be reliably used to guide intervention at this time. We identify a need for high-quality evidence to further examine the efficacy of computer-based auditory training for people with hearing loss.

Perceptual acclimatization post nonlinear frequency compression hearing aid fitting in older children

PURPOSE

In this study, the authors evaluated the effect of frequency compression hearing aids on speech perception ability and the time course and magnitude of acclimatization-related changes.

METHOD

Participants included children ages 11-18 years. Speech perception ability was evaluated over well-controlled baseline, treatment, and withdrawal study phases. Study-worn hearing aids were individually fitted to all participants. The authors evaluated speech perception ability using outcomes of speech detection (/s/ and /[symbol in text]/ sounds), /s-[symbol in text]/ discrimination, and plural and consonant recognition.

RESULTS

Indices of change were discussed on a case-by-case basis across all study phases. Significant treatment effects were measured for all cases, on at least one measure, with some listeners displaying significant acclimatization trends following a trial of frequency compression.

CONCLUSION

Findings suggest that frequency compression provided varying outcomes, both in benefit and acclimatization, across listeners. For some, a period of acclimatization was necessary before change could be measured. For others, performance remained stable over the time course under evaluation, suggesting that some but not all children will experience improved speech recognition ability after a period of frequency compression hearing aid use.

Speech identification with temporal and spectral modification in subjects with auditory neuropathy

Background. The aim of this study was to investigate the individual effects of envelope enhancement and high-pass filtering (500 Hz) on word identification scores in quiet for individuals with Auditory Neuropathy. Method. Twelve individuals with Auditory Neuropathy (six males and six females) with ages ranging from 12 to 40 years participated in the study. Word identification was assessed using bi-syllabic words in each of three speech processing conditions: unprocessed, envelope-enhanced, and high-pass filtered. All signal processing was carried out using MATLAB-7. Results. Word identification scores showed a mean improvement of 18% with envelope enhanced versus unprocessed speech. No significant improvement was observed with high-pass filtered versus unprocessed speech. Conclusion. These results suggest that the compression/expansion signal processing strategy enhances speech identification scores-at least for mild and moderately impaired individuals with AN. In contrast, simple high-pass filtering (i.e., eliminating the low-frequency content of the signal) does not improve speech perception in quiet for individuals with Auditory Neuropathy.

The influence of stop consonants' perceptual features on the Articulation Index model

Studies on consonant perception under noise conditions typically describe the average consonant error as exponential in the Articulation Index (AI). While this AI formula nicely fits the average error over all consonants, it does not fit the error for any consonant at the utterance level. This study analyzes the error patterns of six stop consonants /p, t, k, b, d, g/ with four vowels (/α/, /ε/, /I/, /ae/), at the individual consonant (i.e., utterance) level. The findings include that the utterance error is essentially zero for signal to noise ratios (SNRs) at least -2 dB, for >78% of the stop consonant utterances. For these utterances, the error is essentially a step function in the SNR at the utterance's detection threshold. This binary error dependence is consistent with the audibility of a single binary defining acoustic feature, having zero error above the feature's detection threshold. Also 11% of the sounds have high error, defined as ≥ 20% for SNRs greater than or equal to -2 dB. A grand average across many such sounds, having a natural distribution in thresholds, results in the error being exponential in the AI measure, as observed. A detailed analysis of the variance from the AI error is provided along with a Bernoulli-trials analysis of the statistical significance.

Classification of stop place in consonant-vowel contexts using feature extrapolation of acoustic-phonetic features in telephone speech

Knowledge-based speech recognition systems extract acoustic cues from the signal to identify speech characteristics. For channel-deteriorated telephone speech, acoustic cues, especially those for stop consonant place, are expected to be degraded or absent. To investigate the use of knowledge-based methods in degraded environments, feature extrapolation of acoustic-phonetic features based on Gaussian mixture models is examined. This process is applied to a stop place detection module that uses burst release and vowel onset cues for consonant-vowel tokens of English. Results show that classification performance is enhanced in telephone channel-degraded speech, with extrapolated acoustic-phonetic features reaching or exceeding performance using estimated Mel-frequency cepstral coefficients (MFCCs). Results also show acoustic-phonetic features may be combined with MFCCs for best performance, suggesting these features provide information complementary to MFCCs.

Cortical activity patterns predict robust speech discrimination ability in noise

The neural mechanisms that support speech discrimination in noisy conditions are poorly understood. In quiet conditions, spike timing information appears to be used in the discrimination of speech sounds. In this study, we evaluated the hypothesis that spike timing is also used to distinguish between speech sounds in noisy conditions that significantly degrade neural responses to speech sounds. We tested speech sound discrimination in rats and recorded primary auditory cortex (A1) responses to speech sounds in background noise of different intensities and spectral compositions. Our behavioral results indicate that rats, like humans, are able to accurately discriminate consonant sounds even in the presence of background noise that is as loud as the speech signal. Our neural recordings confirm that speech sounds evoke degraded but detectable responses in noise. Finally, we developed a novel neural classifier that mimics behavioral discrimination. The classifier discriminates between speech sounds by comparing the A1 spatiotemporal activity patterns evoked on single trials with the average spatiotemporal patterns evoked by known sounds. Unlike classifiers in most previous studies, this classifier is not provided with the stimulus onset time. Neural activity analyzed with the use of relative spike timing was well correlated with behavioral speech discrimination in quiet and in noise. Spike timing information integrated over longer intervals was required to accurately predict rat behavioral speech discrimination in noisy conditions. The similarity of neural and behavioral discrimination of speech in noise suggests that humans and rats may employ similar brain mechanisms to solve this problem.

Human phoneme recognition depending on speech-intrinsic variability

The influence of different sources of speech-intrinsic variation (speaking rate, effort, style and dialect or accent) on human speech perception was investigated. In listening experiments with 16 listeners, confusions of consonant-vowel-consonant (CVC) and vowel-consonant-vowel (VCV) sounds in speech-weighted noise were analyzed. Experiments were based on the OLLO logatome speech database, which was designed for a man-machine comparison. It contains utterances spoken by 50 speakers from five dialect/accent regions and covers several intrinsic variations. By comparing results depending on intrinsic and extrinsic variations (i.e., different levels of masking noise), the degradation induced by variabilities can be expressed in terms of the SNR. The spectral level distance between the respective speech segment and the long-term spectrum of the masking noise was found to be a good predictor for recognition rates, while phoneme confusions were influenced by the distance to spectrally close phonemes. An analysis based on transmitted information of articulatory features showed that voicing and manner of articulation are comparatively robust cues in the presence of intrinsic variations, whereas the coding of place is more degraded. The database and detailed results have been made available for comparisons between human speech recognition (HSR) and automatic speech recognizers (ASR).

Children's recognition of American English consonants in noise

In contrast to the availability of consonant confusion studies with adults, to date, no investigators have compared children's consonant confusion patterns in noise to those of adults in a single study. To examine whether children's error patterns are similar to those of adults, three groups of children (24 each in 4-5, 6-7, and 8-9 yrs. old) and 24 adult native speakers of American English (AE) performed a recognition task for 15 AE consonants in /ɑ/-consonant-/ɑ/ nonsense syllables presented in a background of speech-shaped noise. Three signal-to-noise ratios (SNR: 0, +5, and +10 dB) were used. Although the performance improved as a function of age, the overall consonant recognition accuracy as a function of SNR improved at a similar rate for all groups. Detailed analyses using phonetic features (manner, place, and voicing) revealed that stop consonants were the most problematic for all groups. In addition, for the younger children, front consonants presented in the 0 dB SNR condition were more error prone than others. These results suggested that children's use of phonetic cues do not develop at the same rate for all phonetic features.

Consonant identification in consonant-vowel-consonant syllables in speech-spectrum noise

Identification functions of 20 initial and 20 final consonants were characterized in 9600 randomly sampled consonant-vowel-consonant (CVC) tokens presented in speech-spectrum noise. Because of differences in the response criteria for different consonants, signal detection measures were used to quantify identifiability. Consonant-specific baseline signal-to-noise ratios (SNRs) were adjusted to produce a d(') of 2.20 for each consonant. Consonant identification was measured at baseline SNRs (B), at B-6, and at B+6 dB. Baseline SNRs varied by more than 40 dB for different consonants. Confusion analysis revealed that single-feature place-of-articulation errors predominated at the highest SNR, while combined-feature errors predominated at the lowest SNR. Most consonants were identified at lower SNRs in initial than final syllable position. Vowel nuclei (/a/, /i/, or /u/) significantly influenced the identifiability of 85% of consonants, with consistent vowel effects seen for consonant classes defined by manner, voicing, and place. Manner and voicing of initial and final consonants were processed independently, but place cues interacted: initial and final consonants differing in place of articulation were identified more accurately than those sharing the same place. Consonant identification in CVCs reveals contextual complexities in consonant processing.

Consonant confusions in white noise

The classic [MN55] confusion matrix experiment (16 consonants, white noise masker) was repeated by using computerized procedures, similar to those of Phatak and Allen (2007). ["Consonant and vowel confusions in speech-weighted noise," J. Acoust. Soc. Am. 121, 2312-2316]. The consonant scores in white noise can be categorized in three sets: low-error set [/m/, /n/], average-error set [/p/, /t/, /k/, /s/, /[please see text]/, /d/, /g/, /z/, /Z/], and high-error set /f/theta/b/, /v/, /E/,/theta/]. The consonant confusions match those from MN55, except for the highly asymmetric voicing confusions of fricatives, biased in favor of voiced consonants. Masking noise cannot only reduce the recognition of a consonant, but also perceptually morph it into another consonant. There is a significant and systematic variability in the scores and confusion patterns of different utterances of the same consonant, which can be characterized as (a) confusion heterogeneity, where the competitors in the confusion groups of a consonant vary, and (b) threshold variability, where confusion threshold [i.e., signal-to-noise ratio (SNR) and score at which the confusion group is formed] varies. The average consonant error and errors for most of the individual consonants and consonant sets can be approximated as exponential functions of the articulation index (AI). An AI that is based on the peak-to-rms ratios of speech can explain the SNR differences across experiments.

A method to identify noise-robust perceptual features: application for consonant /t/

This study focuses on correlating speech confusion patterns, defined as consonant-vowel confusion as a function of the speech-to-noise ratio, and a model acoustic feature (AF) representation called the AI gram, defined as the articulation index density in the spectrotemporal domain. By collecting many responses from many talkers and listeners, the AF and psychophysical feature (event) is shown to be correlated via the AI-gram model and the confusion matrices at the utterance level, thereby explaining the listener confusion. Consonant /t/ is used as an example to identify its primary robust-to-noise feature, and a precise correlation of the acoustic information with the listeners' confusions is used to label the event. The main spectrotemporal cue defining the /t/ event is an across-frequency temporal coincidence, wherein frequency spread and robustness vary across utterances, while the event remains invariant. The cross-frequency timing event is shown to be the key perceptual feature for consonants in a vowel following context. Coincidences are found to form the basic element of the auditory object. Neural circuits used for coincidence in binaural processing for localization across ears are proposed to be used within one ear across channels. It is further concluded that the event is based on the audibility of the /t/ burst rather than on any superthreshold property.

Perception and confusion of speech sounds by adults with a cochlear implant

The aim of this pilot study was to identify the most common speech sound confusions of 5 Norwegian cochlear implanted post-lingually deafened adults. We played recorded nonwords, aCa, iCi and bVb, to our informants, asked them to repeat what they heard, recorded their repetitions and transcribed these phonetically. We arranged the collected data in confusion matrices to find the most common and most uncommon speech sound confusions. We found that the voiced and unvoiced consonants are seldom confused. We also found that there was a higher rate of consonant confusion for the iCi words than for the aCa words. The most frequent confusion was [eta] perceived as [n], [m] perceived as [n] and [upsilon] perceived as [n]. For the consonants, manner of articulation was rarely confused, but place of articulation was often confused. An exception from this was the confusion of [l] and [n], which differs only in manner of articulation. The latter is in accordance with reports we get from clinicians. We postulate that this is caused by the speech processing of the cochlear implant. We found less confusion of the vowels, which can be explained by the fact that vowels have much higher energy and longer duration than most of the consonants. The most frequent confusion was [a:] perceived as [see text] and [u:] perceived as [see text]. [e:], [i:] and [see text] were never confused with other vowels.

Perception of clear fricatives by normal-hearing and simulated hearing-impaired listeners

Speakers may adapt the phonetic details of their productions when they anticipate perceptual difficulty or comprehension failure on the part of a listener. Previous research suggests that a speaking style known as clear speech is more intelligible overall than casual, conversational speech for a variety of listener populations. However, it is unknown whether clear speech improves the intelligibility of fricative consonants specifically, or how its effects on fricative perception might differ depending on listener population. The primary goal of this study was to determine whether clear speech enhances fricative intelligibility for normal-hearing listeners and listeners with simulated impairment. Two experiments measured babble signal-to-noise ratio thresholds for fricative minimal pair distinctions for 14 normal-hearing listeners and 14 listeners with simulated sloping, recruiting impairment. Results indicated that clear speech helped both groups overall. However, for impaired listeners, reliable clear speech intelligibility advantages were not found for non-sibilant pairs. Correlation analyses comparing acoustic and perceptual data indicated that a shift of energy concentration toward higher frequency regions and greater source strength contributed to the clear speech effect for normal-hearing listeners. Correlations between acoustic and perceptual data were less consistent for listeners with simulated impairment, and suggested that lower-frequency information may play a role.

Individual differences in auditory abilities

Performance on 19 auditory discrimination and identification tasks was measured for 340 listeners with normal hearing. Test stimuli included single tones, sequences of tones, amplitude-modulated and rippled noise, temporal gaps, speech, and environmental sounds. Principal components analysis and structural equation modeling of the data support the existence of a general auditory ability and four specific auditory abilities. The specific abilities are (1) loudness and duration (overall energy) discrimination; (2) sensitivity to temporal envelope variation; (3) identification of highly familiar sounds (speech and nonspeech); and (4) discrimination of unfamiliar simple and complex spectral and temporal patterns. Examination of Scholastic Aptitude Test (SAT) scores for a large subset of the population revealed little or no association between general or specific auditory abilities and general intellectual ability. The findings provide a basis for research to further specify the nature of the auditory abilities. Of particular interest are results suggestive of a familiar sound recognition (FSR) ability, apparently specialized for sound recognition on the basis of limited or distorted information. This FSR ability is independent of normal variation in both spectral-temporal acuity and of general intellectual ability.

Consonant and vowel confusions in speech-weighted noise

This paper presents the results of a closed-set recognition task for 64 consonant-vowel sounds (16 C X 4 V, spoken by 18 talkers) in speech-weighted noise (-22,-20,-16,-10,-2 [dB]) and in quiet. The confusion matrices were generated using responses of a homogeneous set of ten listeners and the confusions were analyzed using a graphical method. In speech-weighted noise the consonants separate into three sets: a low-scoring set C1 (/f/, /theta/, /v/, /d/, /b/, /m/), a high-scoring set C2 (/t/, /s/, /z/, /S/, /Z/) and set C3 (/n/, /p/, /g/, /k/, /d/) with intermediate scores. The perceptual consonant groups are C1: {/f/-/theta/, /b/-/v/-/d/, /theta/-/d/}, C2: {/s/-/z/, /S/-/Z/}, and C3: /m/-/n/, while the perceptual vowel groups are /a/-/ae/ and /epsilon/-/iota/. The exponential articulation index (AI) model for consonant score works for 12 of the 16 consonants, using a refined expression of the AI. Finally, a comparison with past work shows that white noise masks the consonants more uniformly than speech-weighted noise, and shows that the AI, because it can account for the differences in noise spectra, is a better measure than the wideband signal-to-noise ratio for modeling and comparing the scores with different noise maskers.

New perspectives on assessing amplification effects

Clinicians have long been aware of the range of performance variability with hearing aids. Despite improvements in technology, there remain many instances of well-selected and appropriately fitted hearing aids whereby the user reports minimal improvement in speech understanding. This review presents a multistage framework for understanding how a hearing aid affects performance. Six stages are considered: (1) acoustic content of the signal, (2) modification of the signal by the hearing aid, (3) interaction between sound at the output of the hearing aid and the listener's ear, (4) integrity of the auditory system, (5) coding of available acoustic cues by the listener's auditory system, and (6) correct identification of the speech sound. Within this framework, this review describes methodology and research on 2 new assessment techniques: acoustic analysis of speech measured at the output of the hearing aid and auditory evoked potentials recorded while the listener wears hearing aids. Acoustic analysis topics include the relationship between conventional probe microphone tests and probe microphone measurements using speech, appropriate procedures for such tests, and assessment of signal-processing effects on speech acoustics and recognition. Auditory evoked potential topics include an overview of physiologic measures of speech processing and the effect of hearing loss and hearing aids on cortical auditory evoked potential measurements in response to speech. Finally, the clinical utility of these procedures is discussed.

Individual differences in auditory discrimination of spectral shape and speech-identification performance among elderly listeners

Speech-understanding difficulties observed in elderly hearing-impaired listeners are predominantly errors in the recognition of consonants, particularly within consonants that share the same manner of articulation. Spectral shape is an important acoustic cue that serves to distinguish such consonants. The present study examined whether individual differences in speech understanding among elderly hearing-impaired listeners could be explained by individual differences in spectral-shape discrimination ability. This study included a group of 20 elderly hearing-impaired listeners, as well as a group of young normal-hearing adults for comparison purposes. All subjects were tested on speech-identification tasks, with natural and computer-synthesized speech stimuli, and on a series of spectral-shape discrimination tasks. As expected, the young normal-hearing adults performed better than the elderly listeners on many of the identification tasks and on all but two discrimination tasks. Regression analyses of the data from the elderly listeners revealed moderate predictive relationships between some of the spectral-shape discrimination thresholds and speech-identification performance. The results indicated that when all stimuli were at least minimally audible, some of the individual differences in the identification of natural and synthetic speech tokens by elderly hearing-impaired listeners were associated with corresponding differences in their spectral-shape discrimination abilities for similar sounds.

The identification of English consonants by native speakers of Italian

This study examined the identification of English consonants in noise by native speakers of Italian. The effect of age of first exposure to English was evaluated by comparing three groups of subjects who continued to use Italian relatively often but differed according to their age of arrival (AOA) in Canada from Italy (early: 7, mid: 14, late: 19 years). The subjects in the late group made more errors identifying word-initial consonants than subjects in the early group did; however, the effect of AOA was nonsignificant for word-final stops. The effect of amount of native language (L1) use was evaluated by comparing two groups of early bilinguals who were matched for AOA (mean = 7 years) but differed according to self-reported percentage use of Italian (early: 32%, early-low: 8%). The early bilinguals who used Italian often (early) made significantly more errors identifying word-initial and word-final consonants than native English (NE) subjects did, whereas the early bilinguals who used Italian seldom (early-low) did not differ from the NE subjects. The subjects' phonological short-term memory was estimated by having them repeat Italian non-words. This was done in an attempt to identify the source of individual differences. The nonword repetition scores were in fact found to independently account for 15% of the variance in subjects' errors identifying word-final English consonants and 8% of the variance for word-initial consonants.

Perception of voiceless fricatives by normal-hearing and hearing-impaired children and adults

This study examined the perceptual-weighting strategies and performance-audibility functions of 11 moderately hearing-impaired (HI) children, 11 age-matched normal-hearing (NH) children, 11 moderately HI adults, and 11 NH adults. The purpose was to (a) determine the perceptual-weighting strategies of HI children relative to the other groups and (b) determine the audibility required by each group to achieve a criterion level of performance. Stimuli were 4 nonsense syllables (see text). The vowel, transition, and fricative segments of each nonsense syllable were identified along the temporal domain, and each segment was amplified randomly within each syllable during presentation. Point-biserial correlation coefficients were calculated using the amplitude variation of each segment and the correct and incorrect responses for the corresponding syllable. Results showed that for /see text/ and /see text/, all four groups heavily weighted the fricative segments during perception, whereas the vowel and transition segments received little or no weight. For /see text/, relatively low weights were given to each segment by all four groups. For /see text/, the NH children and adults weighted the transition segment more so than the vowel and fricative segments, whereas the HI children and adults weighted all three segments equally low. Performance-audibility functions of the fricative segments of /see text/ and /see text/ were constructed for each group. In general, maximum performance for each group was reached at lower audibility levels for /see text/ than for /see text/ and steeper functions were observed for the HI groups relative to the NH groups. A decision theory approach was used to confirm the audibility required by each group to achieve a > or =90% level of performance. Results showed both hearing sensitivity and age effects. The HI listeners required lower levels of audibility than the NH listeners to achieve similar levels of performance. Likewise, the adult listeners required lower levels of audibility than the children, although this difference was more substantial for the NH listeners than for the HI listeners.

The effect of cue-enhancement on consonant intelligibility in noise: speaker and listener effects

Our previous work (Hazan & Simpson, 1998) has shown that increasing the salience of perceptually important regions of nonsense word and sentence materials aids speech perception in noise. This study aimed to extend these findings by investigating the robustness of these enhancement techniques in improving consonant intelligibility for a range of different speakers and for groups of listeners with different language backgrounds. In Experiment 1, nonsense vowel-consonant-vowel (VCV) tokens produced by two female and two male speakers without phonetic training were annotated to highlight segments of the signal corresponding to the consonant constriction/occlusion and vowel onset/offset regions. These regions were selectively amplified to enhance the cues they contained, then combined with speech-shaped noise at 0 dB SNR and presented to normally hearing listeners. Significant improvements in intelligibility were found for all speakers although the extent of the improvement varied across speakers. In Experiment 2, a subset of these stimuli were presented to two groups of learners of English--a Japanese-L1 group and a Spanish-L1 group--and a new group of native-English controls. Results showed a significant effect of enhancement in all listener-groups and similar speaker effects for the non-native and native English listeners. Error patterns were related to the distance between the phonological systems of listeners' L1 and L2.

Recognition performance for four combinations of FM system and hearing aid microphone signals in adverse listening conditions

OBJECTIVE

Children with moderate to severe hearing loss routinely use personal frequency modulated (FM) systems in the classroom to improve the signal to noise ratio of teacher-directed speech with notable success. Attention is now being given to the ability of these children to hear other students via the hearing aid (HA) microphone while using an FM system. As a result, a variety of FM system and HA microphone combinations have been recommended for classroom use. To date, there are no studies regarding the efficacy of these FM/HA combinations. The purpose of this study was to evaluate recognition performance using four FM/HA combinations and to characterize that performance for stimuli received primarily through FM system and HA microphone transmission.

DESIGN

Recognition performance for FM system and HA microphone signals was evaluated for two symmetrical and two asymmetrical FM/HA combinations using two commercially available FM systems (one conventional and one FM-precedence circuit). Eleven children (ages 9 to 12) with moderate to severe sensorineural hearing loss and eight children (ages 10 to 11) with normal hearing served as subjects. The two symmetrical FM/HA combinations included: 1) binaural FM system and HA microphone input using the conventional FM system, and 2) binaural FM and HA input using the FM-precedence circuit. The conventional FM system was used for the two asymmetrical combinations and included: 1) binaural FM input and monaural HA input, and 2) FM input to one ear and HA input to the other. Stimuli were 33 consonants presented in the form of nonsense syllables. The stimuli were presented through three loudspeakers representing a teacher and two fellow students in a classroom environment. Speech shaped noise was presented through two additional loudspeakers.

RESULTS

In general, no statistically significant differences in recognition performance were found between any of the FM/HA combinations. Mean recognition scores for HA microphone transmission (55%) were significantly poorer than those for FM system transmission (75%). As expected, initial consonants were more easily recognized than final consonants via FM system and HA microphone transmission. However, voiceless consonants were more easily recognized than voiced consonants via HA microphone transmission, which was not predicted on the basis of previous research.

CONCLUSIONS

These results suggest that a certain amount of flexibility is present when choosing an FM/HA combination. However, recognition performance via the HA microphones was consistently poorer than performance via FM transmission. Because relevant material also originates from fellow students (e.g., answering teacher-directed questions), input via the HAs is often as important as information originating from the teacher. The results suggest that attempts to improve performance for signals transmitted through the HA microphones in a classroom setting would benefit children with hearing loss.

Consonant-vowel intensity ratios for maximizing consonant recognition by hearing-impaired listeners

The effect of adjusting the consonant-vowel (C-V) intensity ratio on consonant recognition in 18 subjects with sensorineural hearing impairment was investigated. C-V intensity ratios in a set of 48 vowel-consonant nonsense syllables were adjusted in steps of 3-6 dB depending on the subject's dynamic range of hearing. An increase in consonant intensity is referred to here as consonant enhancement (CE). The value of CE producing the highest consonant recognition score (CRmax) is defined as CEmax. Both CEmax and CRmax were determined for each subject for each of the 48 nonsense syllables. Consonant type was found to have a highly significant effect on CRmax, the gain in consonant recognition, and CEmax. The effect of vowel environment was also significant, but of much smaller magnitude. Audiogram configuration was found to have a small effect and was only significant for CRmax. The results of the study also showed that individualized adjustment of the C-V intensity ratio for each subject and consonant-vowel combination can produce substantial improvements in consonant recognition. These data can be used to estimate upper bounds of performance that, in principle, can be obtained by appropriate adjustment of the C-V intensity ratio.

Normal and hearing-impaired word recognition scores for monosyllabic words in quiet and noise

The effects of noise on word recognition scores were assessed with normal-hearing and hearing-impaired subjects. Fifty-one normal-hearing subjects were tested at 50 dB HL using signal-to-noise ratios (S/Ns) of 5, 10, and 15 dB. Thirty subjects with mild-to-moderate sensorineural hearing losses were tested in quiet and in noise at S/Ns of 10 dB and 15 dB. Monosyllabic words in a Multitalker Noise were selected for testing. Mean scores for the normal-hearing subjects were 45% at the 5 dB S/N, 74% at the 10 dB S/N, and 87% at the 15 dB S/N. For the hearing-impaired subjects, scores were 85% in quiet, 60% at the 15 dB S/N, and 40% at the 10 dB S/N. These results suggest that background noise which is mildly disruptive for normal hearing subjects can be highly disruptive to hearing-impaired subjects. Moreover, these findings indicate that subjects with mild-to-moderate sensorineural hearing loss require a more favourable S/N than normal listeners to achieve comparable word recognition scores. Test-retest differences for word recognition scores revealed variability that agreed closely with predictions based on the binomial distribution for both groups of subjects. Speech-in-noise abilities must be measured directly because regression equations revealed that speech-in-noise scores cannot be predicted accurately from either puretone thresholds or speech-in-quiet scores. Word recognition functions are presented from several hearing-impaired subjects and demonstrate the value of testing in noise.

A computerized adaptive testing system for speech discrimination measurement: the Speech Sound Pattern Discrimination Test

A computerized, adaptive test-delivery system for the measurement of speech discrimination, the Speech Sound Pattern Discrimination Test, is described and evaluated. Using a modified discrimination task, the testing system draws on a pool of 130 items spanning a broad range of difficulty to estimate an examinee's location along an underlying continuum of speech processing ability, yet does not require the examinee to possess a high level of English language proficiency. The system is driven by a mathematical measurement model which selects only test items which are appropriate in difficulty level for a given examinee, thereby individualizing the testing experience. Test items were administered to a sample of young deaf adults, and the adaptive testing system evaluated in terms of respondents' sensory and perceptual capabilities, acoustic and phonetic dimensions of speech, and theories of speech perception. Data obtained in this study support the validity, reliability, and efficiency of this test as a measure of speech processing ability.

Consonant perception with linear and compression amplification

The consonant perception of 15 subjects with mild to moderate sensorineural hearing loss was evaluated using linear amplification and two different types of compression amplification. A specially modified hearing aid was used which allowed for variation of the amplifier input/output function in three steps, such that the compression ratio could be set to 1 (linear), 1.3 or 1.8. The Nonsense Syllable Test (NST) was recorded through the aid in quiet and in two different noise conditions (four-talker babble and a background noise with sharp intermittent sounds), and replayed to the listeners through headphones. No differences in consonant perception were found between the different types of amplification in the quiet condition. In the babble condition, consonant perception was significantly better with linear amplification than with either form of compression. In the sharp noise condition, there was no difference in performance between linear amplification and compression amplification with the ratio of 1.8. Consonant perception was adversely affected, however, by the compression and amplification with the ratio of 1.3 in this condition. Overall NST results and results for particular classes of consonants are discussed.

Binaural cues and consonant perception in reverberation and noise

Although a binaural advantage for understanding speech in adverse listening conditions has long been recognized, little is known about how binaural hearing influences consonant error patterns. The goal of the present study was to examine differences in consonant perception when stimuli distorted by noise and/or reverberation were presented using monaural, binaural, and diotic presentation modes. Results showed significant differences in error patterns among the three listening conditions (noise, reverberation, and reverberation + noise). Differences among the three presentation modes (monaural, binaural, and diotic) were subtle, as were interactions among presentation modes and listening conditions.

Phonemic confusions in quiet and noise for the hearing-impaired

In this study the effects of presentation level and signal-to-noise ratio on phonemic confusions are investigated in 25 hearing-impaired subjects. The confusions of initial consonants, vowels and final consonants in the perception of nonsense CVC words were determined at three presentation levels in quiet and three signal-to-noise ratios in noise. The group results of the different presentation conditions were analyzed by means of INDSCAL analyses. The presence or absence of interfering noise proved to be the most dominant factor: the presence of noise caused a reduced use of low-frequency information. The effects of presentation level are of secondary importance.