Children's performance in complex listening conditions: effects of hearing loss and digital noise reduction

Speech perception in noise, working memory, and attention in children: A scoping review

PURPOSE

Speech perception in noise is an everyday occurrence for adults and children alike. The factors that influence how well individuals cope with noise during spoken communication are not well understood, particularly in the case of children. This article aims to review the available evidence on how working memory and attention play a role in children's speech perception in noise, how characteristics of measures affect results, and how this relationship differs in non-typical populations.

METHOD

This article is a scoping review of the literature available on PubMed. Forty articles were included for meeting the inclusion criteria of including children as participants, some measure of speech perception in noise, some measure of attention and/or working memory, and some attempt to establish relationships between the measures. Findings were charted and presented keeping in mind how they relate to the research questions.

RESULTS

The majority of studies report that attention and especially working memory are involved in speech perception in noise by children. We provide an overview of the impact of certain task characteristics on findings across the literature, as well as how these affect non-typical populations.

CONCLUSION

While most of the work reviewed here provides evidence suggesting that working memory and attention are important abilities employed by children in overcoming the difficulties imposed by noise during spoken communication, methodological variability still prevents a clearer picture from emerging.

Effect of Realistic Test Conditions on Spectral and Temporal Processing in Normal-Hearing Listeners

Purpose To measure the effect of testing conditions (in the soundproof booth vs. quiet room), test order, and number of test sessions on spectral and temporal processing in normal-hearing (NH) listeners. Method Thirty-two adult NH listeners participated in the three experiments. For all three experiments, the stimuli were presented to the left ear at the subjects' most comfortable level through headphones. All tests were administered in an adaptive three-alternative forced-choice paradigm. Experiment 1 was designed to compare the effect of soundproof booth and quiet room test conditions on amplitude modulation detection threshold and modulation frequency discrimination threshold with each of the five modulation frequencies. Experiment 2 was designed to compare the effect of two test orders on the frequency discrimination thresholds under the quiet room test conditions. The thresholds were first measured in the ascending and descending order of four pure tones, and then with counterbalanced order. For Experiment 3, the amplitude discrimination threshold under the quiet room testing condition was assessed 3 times to determine the effect of the number of test sessions. Then the thresholds were compared over the sessions. Results Results showed no significant effect of test environment. The test order is an important variable for frequency discrimination, particularly between piano tunes and pure tones. Results also show no significant difference across test sessions. Conclusions These results suggest that a controlled test environment may not be required in spectral and temporal assessment for NH listeners. Under the quiet test environment, a single outcome measure is sufficient, but test orders should be counterbalanced.

Assistive Hearing Technology for Deaf and Hard-of-Hearing Spoken Language Learners

Radical advancements in hearing technology in the last 30 years have offered some deaf and hard-of-hearing (DHH) children the adequate auditory access necessary to acquire spoken language with high-quality early intervention. However, meaningful achievement gaps in reading and spoken language persist despite the engineering marvel of modern hearing aids and cochlear implants. Moreover, there is enormous unexplained variability in spoken language and literacy outcomes. Aspects of signal processing in both hearing aids and cochlear implants are discussed as they relate to spoken language outcomes in preschool and school-age children. In suggesting areas for future research, a case is made for not only expanding the search for mechanisms of influence on outcomes outside of traditional device- and child-related factors, but also for framing the search within Biopsychosocial systems theories. This theoretical approach incorporates systems of risk factors across many levels, as well as the bidirectional and complex ways in which factors influence each other. The combination of sophisticated hearing technology and a fuller understanding of the complex environmental and biological factors that shape development will help maximize spoken language outcomes in DHH children and contribute to laying the groundwork for successful literacy and academic development.

Effects of Adaptive Hearing Aid Directionality and Noise Reduction on Masked Speech Recognition for Children Who Are Hard of Hearing

Purpose The purpose of this study was to evaluate speech-in-noise and speech-in-speech recognition associated with activation of a fully adaptive directional hearing aid algorithm in children with mild to severe bilateral sensory/neural hearing loss. Method Fourteen children (5-14 years old) who are hard of hearing participated in this study. Participants wore laboratory hearing aids. Open-set word recognition thresholds were measured adaptively for 2 hearing aid settings: (a) omnidirectional (OMNI) and (b) fully adaptive directionality. Each hearing aid setting was evaluated in 3 listening conditions. Fourteen children with normal hearing served as age-matched controls. Results Children who are hard of hearing required a more advantageous signal-to-noise ratio than children with normal hearing to achieve comparable performance in all 3 conditions. For children who are hard of hearing, the average improvement in signal-to-noise ratio when comparing fully adaptive directionality to OMNI was 4.0 dB in noise, regardless of target location. Children performed similarly with fully adaptive directionality and OMNI settings in the presence of the speech maskers. Conclusions Compared to OMNI, fully adaptive directionality improved speech recognition in steady noise for children who are hard of hearing, even when they were not facing the target source. This algorithm did not affect speech recognition when the background noise was speech. Although the use of hearing aids with fully adaptive directionality is not proposed as a substitute for remote microphone systems, it appears to offer several advantages over fixed directionality, because it does not depend on children facing the target talker and provides access to multiple talkers within the environment. Additional experiments are required to further evaluate children's performance under a variety of spatial configurations in the presence of both noise and speech maskers.

Listening effort and working memory capacity in hearing impaired individuals: an integrative literature review

ABSTRACT Purpose: to review the literature on the behavioral methods of listening effort assessment and the working memory capacity recommended for the hearing impaired. Methods: this review was developed through the search of articles in national and international journals, in English and Portuguese, available in Pubmed/Medline, Cochrane Library, Biblioteca Vitual em Saúde - Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) and Scientific Electronic Library Online, between 2007 and 2017. The articles were selected based on the inclusion criteria: articles that used behavioral methods to assess listening effort in hearing-impaired adults, involving the measurement of working memory and its relationship with the listening effort, published in the last 10 years. Results: Twelve articles in which behavioral measures were used to measure listening effort and working memory capacity in the hearing-impaired individuals were reviewed. Their main findings refer to the purpose(s) of the research, participants, behavioral method composed of a primary task (speech perception) and a secondary task (memorization) and results of the studies. Conclusion:the findings of this review allow us to infer that this paradigm is sensitive to measure the listening effort, considering the different instruments used and the population assessed.

Measuring Listening Effort: Convergent Validity, Sensitivity, and Links With Cognitive and Personality Measures

PURPOSE

Listening effort (LE) describes the attentional or cognitive requirements for successful listening. Despite substantial theoretical and clinical interest in LE, inconsistent operationalization makes it difficult to make generalizations across studies. The aims of this large-scale validation study were to evaluate the convergent validity and sensitivity of commonly used measures of LE and assess how scores on those tasks relate to cognitive and personality variables.

METHOD

Young adults with normal hearing (N = 111) completed 7 tasks designed to measure LE, 5 tests of cognitive ability, and 2 personality measures.

RESULTS

Scores on some behavioral LE tasks were moderately intercorrelated but were generally not correlated with subjective and physiological measures of LE, suggesting that these tasks may not be tapping into the same underlying construct. LE measures differed in their sensitivity to changes in signal-to-noise ratio and the extent to which they correlated with cognitive and personality variables.

CONCLUSIONS

Given that LE measures do not show consistent, strong intercorrelations and differ in their relationships with cognitive and personality predictors, these findings suggest caution in generalizing across studies that use different measures of LE. The results also indicate that people with greater cognitive ability appear to use their resources more efficiently, thereby diminishing the detrimental effects associated with increased background noise during language processing.

A critical review of hearing-aid single-microphone noise-reduction studies in adults and children

PURPOSE

Single-microphone noise reduction (SMNR) is implemented in hearing aids to suppress background noise. The purpose of this article was to provide a critical review of peer-reviewed studies in adults and children with sensorineural hearing loss who were fitted with hearing aids incorporating SMNR.

METHOD

Articles published between 2000 and 2016 were searched in PUBMED and EBSCO databases.

RESULTS

Thirty-two articles were included in the final review. Most studies with adult participants showed that SMNR has no effect on speech intelligibility. Positive results were reported for acceptance of background noise, preference, and listening effort. Studies of school-aged children were consistent with the findings of adult studies. No study with infants or young children of under 5 years old was found. Recent studies on noise-reduction systems not yet available in wearable hearing aids have documented benefits of noise reduction on memory for speech processing for older adults.

CONCLUSIONS

This evidence supports the use of SMNR for adults and school-aged children when the aim is to improve listening comfort or reduce listening effort. Future research should test SMNR with infants and children who are younger than 5 years of age. Further development, testing, and clinical trials should be carried out on algorithms not yet available in wearable hearing aids. Testing higher cognitive level for speech processing and learning of novel sounds or words could show benefits of advanced signal processing features. These approaches should be expanded to other populations such as children and younger adults. Implications for rehabilitation The review provides a quick reference for students and clinicians regarding the efficacy and effectiveness of SMNR in wearable hearing aids. This information is useful during counseling session to build a realistic expectation among hearing aid users. Most studies in the adult population suggest that SMNR may provide some benefits to adult listeners in terms of listening comfort, acceptance of background noise, and release of cognitive load in a complex listening condition. However, it does not improve speech intelligibility. Studies that examined SMNR in the paediatric population suggest that SMNR may benefit older school-aged children, aged between 10 and 12 years old. The evidence supports the use of SMNR for adults and school-aged children when the aim is to improve listening comfort or reduce listening effort.

Minimal Hearing Loss: From a Failure-Based Approach to Evidence-Based Practice

PURPOSE

A representative sample of the literature on minimal hearing loss (MHL) was reviewed to provide evidence of challenges faced by children with MHL and to establish the need for evidence-based options for early intervention.

METHOD

Research articles published from 1950 to 2013 were searched in the Medline database using the keywords minimal hearing loss, unilateral hearing loss, and mild hearing loss. References cited in retrieved articles were also reviewed.

RESULTS

In total, 69 articles contained relevant information about pediatric outcomes and/or intervention for unilateral hearing loss, 50 for mild hearing loss, and 6 for high-frequency hearing loss. Six challenges associated with MHL emerged, and 6 interventions were indicated. Evidence indicates that although some individuals may appear to have no observable speech-language or academic difficulties, others experience considerable difficulties. It also indicates that even though children with MHL may appear to catch up in some areas, difficulties in select domains continue into adulthood.

CONCLUSIONS

Evidence indicates significant risks associated with untreated MHL. Evidence also demonstrates the need for early intervention and identifies several appropriate intervention strategies; however, no single protocol is appropriate for all children. Therefore, families should be educated about the impact of MHL and about available interventions so that informed decisions can be made.

Acoustical and Perceptual Comparison of Noise Reduction and Compression in Hearing Aids

PURPOSE

Noise reduction and dynamic-range compression are generally applied together in hearing aids but may have opposite effects on amplification. This study evaluated the acoustical and perceptual effects of separate and combined processing of noise reduction and compression.

DESIGN

Recordings of the output of 4 hearing aids for speech in babble noise at +4 dB signal-to-noise ratio were used in 3 experiments: (a) acoustical measurements to determine the influence of processing on speech and noise levels; (b) perceptual measurements to determine the detectability of processing differences for 16 listeners with hearing impairment; and (c) perceptual measurements to determine the effect of processing on speech intelligibility, noise annoyance, speech naturalness, and overall preference.

RESULTS

Noise reduction and compression processing differed between hearing aids. The combined processing (noise reduction with compression) most strongly reduced noise and speech levels. The combined processing was detectably different between hearing aids, but compression processing alone was not. The combined processing did not influence speech intelligibility. Preference for combined processing was lower than previously observed for noise reduction without compression.

CONCLUSIONS

Differences in processing between hearing aids are perceptually salient. The effect of compression should be taken into account during the development and evaluation of hearing aid noise reduction.

Commentary: listening can be exhausting--fatigue in children and adults with hearing loss

Anecdotal reports of fatigue after sustained speech-processing demands are common among adults with hearing loss; however, systematic research examining hearing loss-related fatigue is limited, particularly with regard to fatigue among children with hearing loss (CHL). Many audiologists, educators, and parents have long suspected that CHL experience stress and fatigue as a result of the difficult listening demands they encounter throughout the day at school. Recent research in this area provides support for these intuitive suggestions. In this article, the authors provide a framework for understanding the construct of fatigue and its relation to hearing loss, particularly in children. Although empirical evidence is limited, preliminary data from recent studies suggest that some CHL experience significant fatigue-and such fatigue has the potential to compromise a child's performance in the classroom. In this commentary, the authors discuss several aspects of fatigue including its importance, definitions, prevalence, consequences, and potential linkage to increased listening effort in persons with hearing loss. The authors also provide a brief synopsis of subjective and objective methods to quantify listening effort and fatigue. Finally, the authors suggest a common-sense approach for identification of fatigue in CHL; and, the authors briefly comment on the use of amplification as a management strategy for reducing hearing-related fatigue.

Measuring listening effort: driving simulator versus simple dual-task paradigm

OBJECTIVES

The dual-task paradigm has been widely used to measure listening effort. The primary objectives of the study were to (1) investigate the effect of hearing aid amplification and a hearing aid directional technology on listening effort measured by a complicated, more real world dual-task paradigm and (2) compare the results obtained with this paradigm to a simpler laboratory-style dual-task paradigm.

DESIGN

The listening effort of adults with hearing impairment was measured using two dual-task paradigms, wherein participants performed a speech recognition task simultaneously with either a driving task in a simulator or a visual reaction-time task in a sound-treated booth. The speech materials and road noises for the speech recognition task were recorded in a van traveling on the highway in three hearing aid conditions: unaided, aided with omnidirectional processing (OMNI), and aided with directional processing (DIR). The change in the driving task or the visual reaction-time task performance across the conditions quantified the change in listening effort.

RESULTS

Compared to the driving-only condition, driving performance declined significantly with the addition of the speech recognition task. Although the speech recognition score was higher in the OMNI and DIR conditions than in the unaided condition, driving performance was similar across these three conditions, suggesting that listening effort was not affected by amplification and directional processing. Results from the simple dual-task paradigm showed a similar trend: hearing aid technologies improved speech recognition performance, but did not affect performance in the visual reaction-time task (i.e., reduce listening effort). The correlation between listening effort measured using the driving paradigm and the visual reaction-time task paradigm was significant. The finding showing that our older (56 to 85 years old) participants' better speech recognition performance did not result in reduced listening effort was not consistent with literature that evaluated younger (approximately 20 years old), normal hearing adults. Because of this, a follow-up study was conducted. In the follow-up study, the visual reaction-time dual-task experiment using the same speech materials and road noises was repeated on younger adults with normal hearing. Contrary to findings with older participants, the results indicated that the directional technology significantly improved performance in both speech recognition and visual reaction-time tasks.

CONCLUSIONS

Adding a speech listening task to driving undermined driving performance. Hearing aid technologies significantly improved speech recognition while driving, but did not significantly reduce listening effort. Listening effort measured by dual-task experiments using a simulated real-world driving task and a conventional laboratory-style task was generally consistent. For a given listening environment, the benefit of hearing aid technologies on listening effort measured from younger adults with normal hearing may not be fully translated to older listeners with hearing impairment.

Nonlinear frequency compression in hearing aids: impact on speech and language development

OBJECTIVES

The research questions of this study were: (1) Are children using nonlinear frequency compression (NLFC) in their hearing aids getting better access to the speech signal than children using conventional processing schemes? The authors hypothesized that children whose hearing aids provided wider input bandwidth would have more access to the speech signal, as measured by an adaptation of the Speech Intelligibility Index, and (2) are speech and language skills different for children who have been fit with the two different technologies; if so, in what areas? The authors hypothesized that if the children were getting increased access to the speech signal as a result of their NLFC hearing aids (question 1), it would be possible to see improved performance in areas of speech production, morphosyntax, and speech perception compared with the group with conventional processing.

DESIGN

Participants included 66 children with hearing loss recruited as part of a larger multisite National Institutes of Health-funded study, Outcomes for Children with Hearing Loss, designed to explore the developmental outcomes of children with mild to severe hearing loss. For the larger study, data on communication, academic and psychosocial skills were gathered in an accelerated longitudinal design, with entry into the study between 6 months and 7 years of age. Subjects in this report consisted of 3-, 4-, and 5-year-old children recruited at the North Carolina test site. All had at least at least 6 months of current hearing aid usage with their NLFC or conventional amplification. Demographic characteristics were compared at the three age levels as well as audibility and speech/language outcomes; speech-perception scores were compared for the 5-year-old groups.

RESULTS

Results indicate that the audibility provided did not differ between the technology options. As a result, there was no difference between groups on speech or language outcome measures at 4 or 5 years of age, and no impact on speech perception (measured at 5 years of age). The difference in Comprehensive Assessment of Spoken Language and mean length of utterance scores for the 3-year-old group favoring the group with conventional amplification may be a consequence of confounding factors such as increased incidence of prematurity in the group using NLFC.

CONCLUSIONS

Children fit with NLFC had similar audibility, as measured by a modified Speech Intelligibility Index, compared with a matched group of children using conventional technology. In turn, there were no differences in their speech and language abilities.

Listening effort and perceived clarity for normal-hearing children with the use of digital noise reduction

OBJECTIVES

The goal of this study was to evaluate how digital noise reduction (DNR) impacts listening effort and judgment of sound clarity in children with normal hearing. It was hypothesized that when two DNR algorithms differing in signal-to-noise ratio (SNR) output are compared, the algorithm that provides the greatest improvement in overall output SNR will reduce listening effort and receive a better clarity rating from child listeners. A secondary goal was to evaluate the relation between the inversion method measurements and listening effort with DNR processing.

DESIGN

Twenty-four children with normal hearing (ages 7 to 12 years) participated in a speech recognition task in which consonant-vowel-consonant nonwords were presented in broadband background noise. Test stimuli were recorded through two hearing aids with DNR off and DNR on at 0 dB and +5 dB input SNR. Stimuli were presented to listeners and verbal response time (VRT) and phoneme recognition scores were measured. The underlying assumption was that an increase in VRT reflects an increase in listening effort. Children rated the sound clarity for each condition. The two commercially available HAs were chosen based on: (1) an inversion technique, which was used to quantify the magnitude of change in SNR with the activation of DNR, and (2) a measure of magnitude-squared coherence, which was used to ensure that DNR in both devices preserved the spectrum.

RESULTS

One device provided a greater improvement in overall output SNR than the other. Both DNR algorithms resulted in minimal spectral distortion as measured using coherence. For both devices, VRT decreased for the DNR-on condition, suggesting that listening effort decreased with DNR in both devices. Clarity ratings were also better in the DNR-on condition for both devices. The device showing the greatest improvement in output SNR with DNR engaged improved phoneme recognition scores. The magnitude of this improved phoneme recognition was not accurately predicted with measurements of output SNR. Measured output SNR varied in the ability to predict other outcomes.

CONCLUSIONS

Overall, results suggest that DNR effectively reduces listening effort and improves subjective clarity ratings in children with normal hearing but that these improvements are not necessarily related to the output SNR improvements or preserved speech spectra provided by the DNR.

The Complexities of Fatigue in Children with Hearing Loss

Fatigue is a common phenomenon in our society, and it can have a major impact on an individual's performance and wellbeing. Parents and teachers have long believed that children with hearing loss (CHL) are at increased risk for fatigue. One could easily speculate that toward the end of a school day, CHL may be “physically and mentally spent” as a result of focusing so intently on a teacher's speech, as well as conversations with other students. Moreover, the increased listening effort, stress, and subsequent fatigue experienced by CHL could jeopardize the ability to learn in a noisy classroom environment, thus increasing the risk for problems in school. Only recently, however, have we begun to see empirical studies supporting the notion that CHL experience more fatigue than children with normal hearing (CNH).

This review was developed to enhance the awareness of fatigue among those audiologists interested in serving CHL. To this end, we have presented an overview on fatigue in CHL, including its importance, definitions, prevalence, consequences, and recent developments. The complexity and multifaceted nature of fatigue has been highlighted and the need for additional research on fatigue in CHL is emphasized.

The Effects of Digital Signal Processing Features on Children's Speech Recognition and Loudness Perception

Purpose

The purpose of this study was to determine the effects of hearing instruments set to Desired Sensation Level version 5 (DSL v5) hearing instrument prescription algorithm targets and equipped with directional microphones and digital noise reduction (DNR) on children's sentence recognition in noise performance and loudness perception in a classroom environment.

Method

Ten children (ages 8–17 years) with stable, congenital sensorineural hearing losses participated in the study. Participants were fitted bilaterally with behind-the-ear hearing instruments set to DSL v5 prescriptive targets. Sentence recognition in noise was evaluated using the Bamford–Kowal–Bench Speech in Noise Test (Niquette et al., 2003). Loudness perception was evaluated using a modified version of the Contour Test of Loudness Perception (Cox, Alexander, Taylor, & Gray, 1997).

Results

Children's sentence recognition in noise performance was significantly better when using directional microphones alone or in combination with DNR than when using omnidirectional microphones alone or in combination with DNR. Children's loudness ratings for sounds above 72 dB SPL were lowest when fitted with the DSL v5 Noise prescription combined with directional microphones. DNR use showed no effect on loudness ratings.

Conclusion

Use of the DSL v5 Noise prescription with a directional microphone improved sentence recognition in noise performance and reduced loudness perception ratings for loud sounds relative to a typical clinical reference fitting with the DSL v5 Quiet prescription with no digital signal processing features enabled. Potential clinical strategies are discussed.

An evidence-based systematic review of directional microphones and digital noise reduction hearing aids in school-age children with hearing loss

PURPOSE

The purpose of this evidence-based systematic review was to evaluate the efficacy of digital noise reduction and directional microphones for outcome measures of audibility, speech recognition, speech and language, and self- or parent-report in pediatric hearing aid users.

METHOD

The authors searched 26 databases for experimental studies published after 1980 addressing one or more clinical questions and meeting all inclusion criteria. The authors evaluated studies for methodological quality and reported or calculated p values and effect sizes when possible.

RESULTS

A systematic search of the literature resulted in the inclusion of 4 digital noise reduction and 7 directional microphone studies (in 9 journal articles) that addressed speech recognition, speech and language, and/or self- or parent-report outcomes. No digital noise reduction or directional microphone studies addressed audibility outcomes.

CONCLUSIONS

On the basis of a moderate level of evidence, digital noise reduction was not found to improve or degrade speech understanding. Additional research is needed before conclusions can be drawn regarding the impact of digital noise reduction on important speech, language, hearing, and satisfaction outcomes. Moderate evidence also indicates that directional microphones resulted in improved speech recognition in controlled optimal settings; however, additional research is needed to determine the effectiveness of directional microphones in actual everyday listening environments.

Age-related benefits of digital noise reduction for short-term word learning in children with hearing loss

PURPOSE

To determine the rate of word learning for children with hearing loss (HL) in quiet and in noise compared to normal-hearing (NH) peers. The effects of digital noise reduction (DNR) were examined for children with HL.

METHOD

Forty-one children with NH and 26 children with HL were grouped by age (8-9 years and 11-12 years). The children learned novel words associated with novel objects through a process of trial and error. Functions relating performance across trials were calculated for each child in each listening condition and were compared.

RESULTS

Significant effects were observed for age (older > younger) in the children with NH and listening condition (quiet > noise) in the children with HL. Significant effects of hearing status were also observed across groups (NH > HL), indicating that the children with HL required more trials to learn the new words. However, word learning improved significantly in noise with the use of DNR for the older but not for the younger children with HL. Hearing aid history and signal-to-noise ratio did not contribute to performance.

CONCLUSION

Word learning was significantly reduced in younger children, in noise, and in the presence of hearing loss. Age-related benefits of DNR were apparent for children over 10 years of age.