A comparison of response time and word recognition measures using a word-monitoring and closed-set identification task

The effect of training on sensitivity and stability of double fusion in Panum's limiting case

Panum's limiting case is a phenomenon of monocular occlusion in binocular vision. This occurs when one object is occluded by the other object for one eye, but the two objects are both visible for the other eye. Although previous studies have found that vertical gradient of horizontal disparity and cue conflict are two important factors for double fusion, the effect of training on the sensitivity and stability of Panum's limiting case remains unknown. The current study trained 26 participants for 5 days with several of Panum's configurations (Gilliam, Frisby, and Wang series). The latency and duration of double fusion were recorded to examine the effects of training on sensitivity and stability of double fusion in Panum's limiting case. For each level of vertical gradient of horizontal disparity and cue conflict, the latency of double fusion decreased and the duration of double fusion increased with each additional training session. The results showed that vertical gradient of horizontal disparity and cue conflict interacted, and the duration of high cue conflict was significantly shorter than that of medium and low cue conflict for each level of vertical gradient of horizontal disparity. The findings suggest that there is an effect of training for vertical gradient of horizontal disparity and cue conflict in Panum's limiting case, and that the three factors jointly affect the sensitivity and stability of double fusion.

Effects of Spatial Speech Presentation on Listener Response Strategy for Talker-Identification

This study investigates effects of spatial auditory cues on human listeners' response strategy for identifying two alternately active talkers (“turn-taking” listening scenario). Previous research has demonstrated subjective benefits of audio spatialization with regard to speech intelligibility and talker-identification effort. So far, the deliberate activation of specific perceptual and cognitive processes by listeners to optimize their task performance remained largely unexamined. Spoken sentences selected as stimuli were either clean or degraded due to background noise or bandpass filtering. Stimuli were presented via three horizontally positioned loudspeakers: In a non-spatial mode, both talkers were presented through a central loudspeaker; in a spatial mode, each talker was presented through the central or a talker-specific lateral loudspeaker. Participants identified talkers via speeded keypresses and afterwards provided subjective ratings (speech quality, speech intelligibility, voice similarity, talker-identification effort). In the spatial mode, presentations at lateral loudspeaker locations entailed quicker behavioral responses, which were significantly slower in comparison to a talker-localization task. Under clean speech, response times globally increased in the spatial vs. non-spatial mode (across all locations); these “response time switch costs,” presumably being caused by repeated switching of spatial auditory attention between different locations, diminished under degraded speech. No significant effects of spatialization on subjective ratings were found. The results suggested that when listeners could utilize task-relevant auditory cues about talker location, they continued to rely on voice recognition instead of localization of talker sound sources as primary response strategy. Besides, the presence of speech degradations may have led to increased cognitive control, which in turn compensated for incurring response time switch costs.

Development of an 80-word clinical version of the modified rhyme test (MRT80)

The modified rhyme test [MRT; House, Williams, Hecker, and Kryter. (1965). J. Acoust. Soc. Am. 37, 158-166] is a widely used test for measuring the intelligibility of communication systems [ANSI (2009). S3.2 (American National Standards Institute, New York)] but has never gained widespread acceptance as a clinical test of speech intelligibility for listeners who are hearing impaired (HI). In this study, a clinical version of the MRT consisting of two 80-word lists was developed and tested on 2394 service members with varying levels of hearing loss. The test used a factorial design incorporating two speech levels [70 and 78 dB sound pressure level (SPL)], two signal-to-noise ratios (+4 and -4 dB), and two binaural conditions (diotic and binaural). High-frequency emphasis reduced the impact of audibility for HI listeners, focusing the test on the distortion component of hearing loss. The results show that listeners with normal hearing (NH) obtained an average score of 80% correct on the MRT₈₀ test. Listeners with a moderate hearing impairment scored an average of 70% correct. The overall level had little impact on performance for either NH or HI listeners. The results demonstrate that the MRT₈₀ test could be a useful test to assess the distortion effects of hearing loss on speech intelligibility, particularly in cases where it is desirable to use a closed-set test for automatic administration.

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.

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 effects of limited bandwidth and noise on verbal processing time and word recall in normal-hearing children

OBJECTIVES

Understanding speech in acoustically degraded environments can place significant cognitive demands on school-age children who are developing the cognitive and linguistic skills needed to support this process. Previous studies suggest the speech understanding, word learning, and academic performance can be negatively impacted by background noise, but the effect of limited audibility on cognitive processes in children has not been directly studied. The aim of the present study was to evaluate the impact of limited audibility on speech understanding and working memory tasks in school-age children with normal hearing.

DESIGN

Seventeen children with normal hearing between 6 and 12 years of age participated in the present study. Repetition of nonword consonant-vowel-consonant stimuli was measured under conditions with combinations of two different signal to noise ratios (SNRs; 3 and 9 dB) and two low-pass filter settings (3.2 and 5.6 kHz). Verbal processing time was calculated based on the time from the onset of the stimulus to the onset of the child's response. Monosyllabic word repetition and recall were also measured in conditions with a full bandwidth and 5.6 kHz low-pass cutoff.

RESULTS

Nonword repetition scores decreased as audibility decreased. Verbal processing time increased as audibility decreased, consistent with predictions based on increased listening effort. Although monosyllabic word repetition did not vary between the full bandwidth and 5.6 kHz low-pass filter condition, recall was significantly poorer in the condition with limited bandwidth (low pass at 5.6 kHz). Age and expressive language scores predicted performance on word recall tasks, but did not predict nonword repetition accuracy or verbal processing time.

CONCLUSIONS

Decreased audibility was associated with reduced accuracy for nonword repetition and increased verbal processing time in children with normal hearing. Deficits in free recall were observed even under conditions where word repetition was not affected. The negative effects of reduced audibility may occur even under conditions where speech repetition is not impacted. Limited stimulus audibility may result in greater cognitive effort for verbal rehearsal in working memory and may limit the availability of cognitive resources to allocate to working memory and other processes.

Subjective and psychophysiological indexes of listening effort in a competing-talker task

BACKGROUND

The effects of noise and other competing backgrounds on speech recognition performance are well documented. There is less information, however, on listening effort and stress experienced by listeners during a speech-recognition task that requires inhibition of competing sounds.

PURPOSE

The purpose was (a) to determine if psychophysiological indexes of listening effort were more sensitive than performance measures (percentage correct) obtained near ceiling level during a competing speech task, (b) to determine the relative sensitivity of four psychophysiological measures to changes in task demand, and (c) to determine the relationships between changes in psychophysiological measures and changes in subjective ratings of stress and workload.

RESEARCH DESIGN

A repeated-measures experimental design was used to examine changes in performance, psychophysiological measures, and subjective ratings in response to increasing task demand.

STUDY SAMPLE

Fifteen adults with normal hearing participated in the study. The mean age of the participants was 27 (range: 24-54).

DATA COLLECTION AND ANALYSIS

Psychophysiological recordings of heart rate, skin conductance, skin temperature, and electromyographic (EMG) activity were obtained during listening tasks of varying demand. Materials from the Dichotic Digits Test were used to modulate task demand. The three levels of task demand were single digits presented to one ear (low-demand reference condition), single digits presented simultaneously to both ears (medium demand), and a series of two digits presented simultaneously to both ears (high demand). Participants were asked to repeat all the digits they heard, while psychophysiological activity was recorded simultaneously. Subjective ratings of task load were obtained after each condition using the National Aeronautics and Space Administration Task Load Index questionnaire. Repeated-measures analyses of variance were completed for each measure using task demand and session as factors.

RESULTS

Mean performance was higher than 96% for all listening tasks. There was no significant change in performance across listening conditions for any listener. There was, however, a significant increase in mean skin conductance and EMG activity as task demand increased. Heart rate and skin temperature did not change significantly. There was no strong association between subjective and psychophysiological measures, but all participants with mean normalized effort ratings of greater than 4.5 (i.e., effort increased by a factor of at least 4.5) showed significant changes in skin conductance.

CONCLUSIONS

Even in the absence of substantial performance changes, listeners may experience changes in subjective and psychophysiological responses consistent with the activation of a stress response. Skin conductance appears to be the most promising measure for evaluating individual changes in psychophysiological responses during listening tasks.

Speech signal modification to increase intelligibility in noisy environments

The role of transient speech components on speech intelligibility was investigated. Speech was decomposed into two components--quasi-steady-state (QSS) and transient--using a set of time-varying filters whose center frequencies and bandwidths were controlled to identify the strongest formant components in speech. The relative energy and intelligibility of the QSS and transient components were compared to original speech. Most of the speech energy was in the QSS component, but this component had low intelligibility. The transient component had much lower energy but was almost as intelligible as the original speech, suggesting that the transient component included speech elements important to speech perception. A modified version of speech was produced by amplifying the transient component and recombining it with the original speech. The intelligibility of the modified speech in background noise was compared to that of the original speech, using a psychoacoustic procedure based on the modified rhyme protocol. Word recognition rates for the modified speech were significantly higher at low signal-to-noise ratios (SNRs), with minimal effect on intelligibility at higher SNRs. These results suggest that amplification of transient information may improve the intelligibility of speech in noise and that this improvement is more effective in severe noise conditions.

A comparison between vocal reaction time and word recognition measures of children with APD and age-matched peers using auditory word discrimination test

The purpose of this study was to investigate the possibility of improving speech recognition testing sensitivity in children with auditory processing disorders (APD) by incorporating response time measures. A group of children identified in a clinical setting as having APD was compared to an age-matched peer group using a vocal reaction time (VRT) format. The participants were between the ages of 5.5 and 15 years. All children were presented spoken monosyllabic words of the clinical Hebrew speech discrimination test. Statistically significant differences were found, with means in the APD children reflecting slower performance than that of their peers. The two groups did not differ in their performance accuracy. These data show that combining response time measures with percent correct scores improved test sensitivity. Such an approach may hold promise for future clinical applications in the assessment of APD.

Use of a simultaneous sentence perception test to enhance sensitivity to ease of listening

The purpose of the study was to determine if a divided-attention, sentence-recall task was more sensitive to distortion of the speech signal than a conventional focused-attention task. The divided-attention task required listeners to repeat both of two sentences delivered simultaneously to the same ear. The focused-attention task required listeners to repeat a single sentence presented to one ear in quiet or in amplitude-modulated noise (0 dB signal-to-noise ratio). Distortion was introduced by peak clipping. Eighteen listeners with normal hearing were tested under three levels of peak clipping: 0 dB, 11 dB, and 29 dB (re: waveform peak). The effects of clipping were similar, on average, for simultaneous sentences and single sentences in noise. When data were separated by sentence length, however, the effects of clipping were found to be greater for the simultaneous-sentence task, but only for the short sentences (6 words or fewer). The simultaneous-sentence test, in its present form, is not more sensitive to the effects of clipping than is a single-sentence test in noise. Modification of the simultaneous-sentence test to include only short sentences, however, may provide greater test sensitivity than more conventional tests using single sentences in noise.

Response time and word recognition using a Modified-Rhyme monitoring task: list equivalency and time-order effects

OBJECTIVE

The purpose of this study was to assess list equivalency and time-order effects of word recognition scores and response time measures obtained using a digital recording of the Modified Rhyme Test (MRT) with a response time monitoring task (Mackersie, Neuman, & Levitt, 1999).

DESIGN

Response times and percent correct measures were obtained from listeners with normal hearing using the MRT materials presented at a signal to noise ratio of +3 dB. Listeners were tested using a word-monitoring task in which six alternatives were presented in series and listeners pushed a button when they heard the target word (as displayed on the computer monitor). Listeners were tested in two sessions. During each session each of the six MRT lists was administered once. Time-order effects were examined both between and within test sessions.

RESULTS

All lists were equivalent for both speech recognition accuracy and response time except List 1, which showed slightly higher percent correct scores than the other lists. Varied patterns of systematic change over time were observed in 75% of the listeners for the response time measures and for 33% of the listeners for the percent correct measures.

CONCLUSIONS

Lists 2 through 6 of this version of the MRT are equivalent, with List 1 producing slightly higher word recognition scores. Systematic changes over time in response time data for the majority of listeners suggest the need for careful implementation of the test to avoid time-order effects.