Acoustic change complex for assessing speech discrimination in normal-hearing and hearing-impaired infants.

OBJECTIVE: This study examined (1) the utility of a clinical system to record acoustic change complex (ACC, an event-related potential recorded by electroencephalography) for assessing speech discrimination in infants, and (2) the relationship between ACC and functional performance in real life. METHODS: Participants included 115 infants (43 normal-hearing, 72 hearing-impaired), aged 3-12 months. ACCs were recorded using [szs], [uiu], and a spectral rippled noise high-pass filtered at 2 kHz as stimuli. Assessments were conducted at age 3-6 months and at 7-12 months. Functional performance was evaluated using a parent-report questionnaire, and correlations with ACC were examined. RESULTS: The rates of onset and ACC responses of normal-hearing infants were not significantly different from those of aided infants with mild or moderate hearing loss but were significantly higher than those with severe loss. On average, response rates measured at 3-6 months were not significantly different from those at 7-12 months. Higher rates of ACC responses were significantly associated with better functional performance. CONCLUSIONS: ACCs demonstrated auditory capacity for discrimination in infants by 3-6 months. This capacity was positively related to real-life functional performance. SIGNIFICANCE: ACCs can be used to evaluate the effectiveness of amplification and monitor development in aided hearing-impaired infants.

Automated cortical auditory response detection strategy.

Objective: This study describes a new automated strategy to determine the detection status of an electrophysiological response.Design: Response, noise and signal-to-noise ratio of the cortical auditory evoked potential (CAEP) were characterised. Detection rules were defined: when to start testing, when to conduct subsequent statistical tests using residual noise as an objective criterion, and when to stop testing.Study sample: Simulations were run to determine optimal parameters on a large combined CAEP data set collected in 45 normal-hearing adults and 17 adults with hearing loss.Results: The proposed strategy to detect CAEPs is fully automated. The first statistical test is conducted when the residual noise level is equal to or smaller than 5.1 µV. The succeeding Hotelling's T2 statistical tests are conducted using pre-defined residual noise levels criteria ranging from 5.1 to 1.2 µV. A rule was introduced allowing to stop testing before the maximum number of recorded epochs is reached, depending on a minimum p-value criterion.Conclusion: The proposed framework can be applied to systems which involves detection of electrophysiological responses in biological systems containing background noise. The proposed detection algorithm which optimise sensitivity, specificity, and recording time has the potential to be used in clinical setting.

The development of the listening in spatialised noise - universal test (LiSN-U) and preliminary evaluation in English-speaking listeners.

Objective: To create a language independent version of the Listening in Spatialised Noise - Sentences test (LiSN-S) and evaluate it in an English-speaking population.Design: Test development and normative data collection. LiSN-Universal (LiSN-U) targets consisted of CVCV pseudo-words (e.g. /mupa/). Two looped distracter tracks consisted of CVCVCVCV pseudo-words. The listener's task was to repeat back the target pseudo-words. Stimuli were presented over headphones using an iPad. Speech reception thresholds were measured adaptively. In the co-located condition all stimuli came from directly in front. In the spatially-separated condition the distracters emanated from +90° and -90° azimuth. Perceived location was manipulated using head-related transfer functions. Spatial advantage was calculated as the difference in dB between the co-located and spatially separated conditions.Study samples: Stimulus intelligibility data were collected from 20 adults. Normative data were collected from native English speakers (23 adults and 127 children).Results: Children's spatially separated, co-located, and spatial advantage results improved significantly with age. Spatial advantage was 4-6 dB larger in the LiSN-U than LiSN-S depending on age group.Conclusion: Whereas additional research in non-native English populations is required, the LiSN-U appears to be an effective tool for measuring spatial processing ability.

Effects of lifetime noise exposure on the middle-age human auditory brainstem response, tinnitus and speech-in-noise intelligibility.

Recent animal studies have shown that the synapses between inner hair cells and the dendrites of the spiral ganglion cells they innervate are the elements in the cochlea most vulnerable to excessive noise exposure. Particularly in rodents, several studies have concluded that exposure to high level octave-band noise for 2 h leads to an irreversible loss of around 50% of synaptic ribbons, leaving audiometric hearing thresholds unaltered. Cochlear synaptopathy following noise exposure is hypothesized to degrade the neural encoding of sounds at the subcortical level, which would help explain certain listening-in-noise difficulties reported by some subjects with otherwise 'normal' hearing. In response to this peripheral damage, increased gain of central stages of the auditory system has been observed across several species of mammals, particularly in association with tinnitus. The auditory brainstem response (ABR) wave I amplitude and waves I-V amplitude ratio have been suggested as non-invasive indicators of cochlear synaptopathy and central gain activation respectively, but the evidence for these hearing disorders in humans is inconclusive. In this study, we evaluated the influence of lifetime noise exposure (LNE) on the human ABR and on speech-in-noise intelligibility performance in a large cohort of adults aged 29 to 55. Despite large inter-subject variability, results showed a moderate, but statistically significant, negative correlation between the ABR wave I amplitude and LNE, consistent with cochlear synaptopathy. The results also showed (a) that central gain mechanisms observed in animal studies might also occur in humans, in which higher stages of the auditory pathway appear to compensate for reduced input from the cochlea; (b) that tinnitus was associated with activation of central gain mechanisms; (c) that relevant cognitive and subcortical factors influence speech-in-noise intelligibility, in particular, longer ABR waves I-V interpeak latencies were associated with poorer performance in understanding speech in noise when central gain mechanisms were active; and (d) absence of a significant relationship between LNE and tinnitus, central gain activation or speech-in-noise performance. Although this study supports the possible existence of cochlear synaptopathy in humans, the great degree of variability, the lack of uniformity in central gain activation and the significant involvement of attention in speech-in-noise performance suggests that noise-induced cochlear synaptopathy is, at most, one of several factors that play a role in humans' speech-in-noise performance.

Hearing tests are just child's play: the sound scouts game for children entering school.

OBJECTIVE: To create a hearing test useable without the involvement of a clinician or calibrated equipment, suitable for children aged 5 or older. DESIGN: The tablet-based app (Sound Scouts) includes tests of speech in quiet, speech in noise and tones in noise, all embedded in game designed to maintain attention. Data were collected to intelligibility-equalize the stimuli, establish normative performance, and evaluate the sensitivity with which Sound Scouts detected known hearing problems and identified their type. STUDY SAMPLE: Participants were children from age 5 to 14 (394 with normal hearing, 97 with previously identified hearing loss) and 50 adults with normal hearing. RESULTS: With pass-fail criteria set such that 98% of children with normal hearing passed Sound Scouts, 85% of children with hearing loss failed Sound Scouts (after exclusion of children in either group who received an inconclusive result or had incomplete results). No child with four-frequency average hearing thresholds of 30 dB HL or greater in their poorer ear passed Sound Scouts. Hearing loss type was correctly identified in only two-thirds of those cases where the algorithm attempted to identify a single type of loss. CONCLUSIONS: Sound Scouts has specificity and sensitivity sufficiently high to provide hearing screening around the time children typically enter school.

The effects of noise exposure and musical training on suprathreshold auditory processing and speech perception in noise.

Recent animal research has shown that exposure to single episodes of intense noise causes cochlear synaptopathy without affecting hearing thresholds. It has been suggested that the same may occur in humans. If so, it is hypothesized that this would result in impaired encoding of sound and lead to difficulties hearing at suprathreshold levels, particularly in challenging listening environments. The primary aim of this study was to investigate the effect of noise exposure on auditory processing, including the perception of speech in noise, in adult humans. A secondary aim was to explore whether musical training might improve some aspects of auditory processing and thus counteract or ameliorate any negative impacts of noise exposure. In a sample of 122 participants (63 female) aged 30-57 years with normal or near-normal hearing thresholds, we conducted audiometric tests, including tympanometry, audiometry, acoustic reflexes, otoacoustic emissions and medial olivocochlear responses. We also assessed temporal and spectral processing, by determining thresholds for detection of amplitude modulation and temporal fine structure. We assessed speech-in-noise perception, and conducted tests of attention, memory and sentence closure. We also calculated participants' accumulated lifetime noise exposure and administered questionnaires to assess self-reported listening difficulty and musical training. The results showed no clear link between participants' lifetime noise exposure and performance on any of the auditory processing or speech-in-noise tasks. Musical training was associated with better performance on the auditory processing tasks, but not the on the speech-in-noise perception tasks. The results indicate that sentence closure skills, working memory, attention, extended high frequency hearing thresholds and medial olivocochlear suppression strength are important factors that are related to the ability to process speech in noise.

Cortical Auditory-Evoked Potentials in Response to Multitone Stimuli in Hearing-Impaired Adults.

PURPOSE: To determine if one-octave multitone (MT) stimuli increase the amplitude of cortical auditory-evoked potentials (CAEPs) in individuals with a hearing loss when compared to standard pure-tone (PT) stimuli and narrow-band noise (NBN). RESEARCH DESIGN: CAEPs were obtained from 16 hearing-impaired adults in response to PT and MT auditory stimuli centered around 0.5, 1, 2, and 4 kHz and NBN centered around 1 and 2 kHz. Hearing impairment ranged from a mild to a moderate hearing loss in both ears. Auditory stimuli were monaurally delivered through insert earphones at 10 and 20 dB above threshold. The root mean square amplitude of the CAEP and the detectability of the responses using Hotelling's T² were calculated and analyzed. RESULTS: CAEP amplitudes elicited with MT stimuli were on average 29% larger than PT stimuli for frequencies centered around 1, 2, and 4 kHz. No significant difference was found for responses to 0.5-kHz stimuli. Significantly higher objective detection scores were found for MT when compared to PT. For the 1- and 2-kHz stimuli, the CAEP amplitudes to NBN were not significantly different to those evoked by PT but a significant difference was found between MT stimuli and both NBN and PT. The mean detection sensitivity of MT for the four frequencies was 80% at 10 dB SL and 95% at 20 dB SL, and was comparable with detection sensitivities observed in normal-hearing participants. CONCLUSIONS: Using MT stimuli when testing CAEPs in adults with hearing impairment showed larger amplitudes and a higher objective detection sensitivity compared to using traditional PT stimuli for frequencies centered around 1, 2, and 4 kHz. These findings suggest that MT stimuli are a clinically useful tool to increase the efficiency of frequency-specific CAEP testing in adults with hearing impairment.

An evaluation of the performance of two binaural beamformers in complex and dynamic multitalker environments.

OBJECTIVE: Binaural beamformers are super-directional hearing aids created by combining microphone outputs from each side of the head. While they offer substantial improvements in SNR over conventional directional hearing aids, the benefits (and possible limitations) of these devices in realistic, complex listening situations have not yet been fully explored. In this study we evaluated the performance of two experimental binaural beamformers. DESIGN: Testing was carried out using a horizontal loudspeaker array. Background noise was created using recorded conversations. Performance measures included speech intelligibility, localization in noise, acceptable noise level, subjective ratings, and a novel dynamic speech intelligibility measure. STUDY SAMPLE: Participants were 27 listeners with bilateral hearing loss, fitted with BTE prototypes that could be switched between conventional directional or binaural beamformer microphone modes. RESULTS: Relative to the conventional directional microphones, both binaural beamformer modes were generally superior for tasks involving fixed frontal targets, but not always for situations involving dynamic target locations. CONCLUSIONS: Binaural beamformers show promise for enhancing listening in complex situations when the location of the source of interest is predictable.

Bigger Is Better: Increasing Cortical Auditory Response Amplitude Via Stimulus Spectral Complexity.

OBJECTIVE: To determine the influence of auditory stimuli spectral characteristics on cortical auditory evoked potentials (CAEPs). DESIGN: CAEPs were obtained from 15 normal-hearing adults in response to six multitone (MT), four pure-tone (PT), and two narrowband noise stimuli. The sounds were presented at 10, 20, and 40 dB above threshold, which were estimated behaviorally beforehand. The root mean square amplitude of the CAEP and the detectability of the response were calculated and analyzed. RESULTS: Amplitudes of the CAEPs to the MT were significantly larger compared with PT for stimuli with frequencies centered around 1, 2, and 4 kHz, whereas no significant difference was found for 0.5 kHz. The objective detection score for the MT was significantly higher compared with the PT. For the 1- and 2-kHz stimuli, the CAEP amplitudes to narrowband noise were not significantly different than those evoked by PT. CONCLUSION: The study supports the notion that spectral complexity, not just bandwidth, has an impact on the CAEP amplitude for stimuli with center frequency above 0.5 kHz. The implication of these findings is that the clinical test time required to estimate thresholds can potentially be decreased by using complex band-limited MT rather than conventional PT stimuli.

Allowing for asymmetric distributions when comparing auditory processing test percentage scores with normative data.

BACKGROUND: Raw percentage scores can be transformed to age-specific Z scores, despite the asymmetric distribution of normative data using a process that is applicable to any percentage (or proportion)-based result. PURPOSE: Normative values are generated for the commonly used dichotic digit and frequency pattern behavioral tests of auditory processing. STUDY SAMPLE: A total of 180 normal-hearing children aged 7 yr 0 mo to 12 yr 2 mo took part in this study. RESEARCH DESIGN: A transformation and regression method is incorporated that allows for the asymmetric distribution of normative results and the development of the response across the 7-12-yr-age range. DATA COLLECTION AND ANALYSIS: Percentage correct scores were determined for each ear in the dichotic digit and frequency pattern tests, delivered at 50 dB HL. The scores were arcsine transformed, then regressed against using an exponential equation, providing an age specific estimated mean score. The residual error of the regression was then used to estimate age specific variance. RESULTS AND CONCLUSIONS: The ability to express results along an age continuum (while accounting for the asymmetric distribution and significant developmental influences) as a standard unit across all ages enables a simplified expression of performance ability on a task.

Least-squares (LS) deconvolution of a series of overlapping cortical auditory evoked potentials: a simulation and experimental study.

OBJECTIVE: To evaluate the viability of disentangling a series of overlapping 'cortical auditory evoked potentials' (CAEPs) elicited by different stimuli using least-squares (LS) deconvolution, and to assess the adaptation of CAEPs for different stimulus onset-asynchronies (SOAs). APPROACH: Optimal aperiodic stimulus sequences were designed by controlling the condition number of matrices associated with the LS deconvolution technique. First, theoretical considerations of LS deconvolution were assessed in simulations in which multiple artificial overlapping responses were recovered. Second, biological CAEPs were recorded in response to continuously repeated stimulus trains containing six different tone-bursts with frequencies 8, 4, 2, 1, 0.5, 0.25 kHz separated by SOAs jittered around 150 (120-185), 250 (220-285) and 650 (620-685) ms. The control condition had a fixed SOA of 1175 ms. In a second condition, using the same SOAs, trains of six stimuli were separated by a silence gap of 1600 ms. Twenty-four adults with normal hearing (<20 dB HL) were assessed. MAIN RESULTS: Results showed disentangling of a series of overlapping responses using LS deconvolution on simulated waveforms as well as on real EEG data. The use of rapid presentation and LS deconvolution did not however, allow the recovered CAEPs to have a higher signal-to-noise ratio than for slowly presented stimuli. The LS deconvolution technique enables the analysis of a series of overlapping responses in EEG. SIGNIFICANCE: LS deconvolution is a useful technique for the study of adaptation mechanisms of CAEPs for closely spaced stimuli whose characteristics change from stimulus to stimulus. High-rate presentation is necessary to develop an understanding of how the auditory system encodes natural speech or other intrinsically high-rate stimuli.

Deconvolution of overlapping cortical auditory evoked potentials recorded using short stimulus onset-asynchrony ranges.

OBJECTIVE: The first aim of this study is to validate the theoretical framework of least-squares (LS) deconvolution on experimental data. The second is to investigate the waveform morphology of the cortical auditory evoked potential (CAEP) for five stimulus onset-asynchronies (SOAs) and effects of alternating stimulus frequency in normally hearing adults. METHODS: Eleven adults (19-55 years) with normal hearing were investigated using tone-burst stimuli of 500 and 2000 Hz with SOAs jittered around 150, 250, 450, and 850 ms in a paired-interval paradigm with fixed or alternating stimulus frequency. RESULTS: The LS deconvolution technique disentangled the overlapping responses, which then provided the following insights. The CAEP amplitude reached a minimum value for SOAs jittered around 450 ms, in contrast with significantly larger amplitudes for SOAs jittered around 150 and 850 ms. Despite this, longer latencies of N1 and P2 consistently occurred for decreasing SOAs. Alternating stimulus frequency significantly increased the amplitude of the CAEP response and decreased latencies for SOAs jittered around 150 ms. Effects of SOAs and alternating stimuli on CAEP amplitude can be modelled using a quantitative model of latent inhibition. CONCLUSIONS: LS deconvolution allows correction for cortical response overlap. The amplitude of the CAEP is sensitive to SOA and stimulus frequency alternation. SIGNIFICANCE: CAEPs are emerging as an important tool in the objective evaluation of hearing aid and cochlear implant fittings. Responses to closely spaced stimuli provide objective information about integration and inhibition mechanisms in the auditory cortex.

Cortical auditory-evoked potentials (CAEPs) in adults in response to filtered speech stimuli.

BACKGROUND: Previous studies have demonstrated that cortical auditory-evoked potentials (CAEPs) can be reliably elicited in response to speech stimuli in listeners wearing hearing aids. It is unclear, however, how close to the aided behavioral threshold (i.e., at what behavioral sensation level) a sound must be before a cortical response can reliably be detected. PURPOSE: The purpose of this study was to systematically examine the relationship between CAEP detection and the audibility of speech sounds (as measured behaviorally), when the listener is wearing a hearing aid fitted to prescriptive targets. A secondary aim was to investigate whether CAEP detection is affected by varying the frequency emphasis of stimuli, so as to simulate variations to the prescribed gain-frequency response of a hearing aid. The results have direct implications for the evaluation of hearing aid fittings in nonresponsive adult clients, and indirect implications for the evaluation of hearing aid fittings in infants. RESEARCH DESIGN: Participants wore hearing aids while listening to speech sounds presented in a sound field. Aided thresholds were measured, and cortical responses evoked, under a range of stimulus conditions. The presence or absence of CAEPs was determined by an automated statistic. STUDY SAMPLE: Participants were adults (6 females and 4 males). Participants had sensorineural hearing loss ranging from mild to severe-profound in degree. DATA COLLECTION AND ANALYSIS: Participants' own hearing aids were replaced with a test hearing aid, with linear processing, during assessments. Pure-tone thresholds and hearing aid gain measurements were obtained, and a theoretical prediction of speech stimulus audibility for each participant (similar to those used for audibility predictions in infant hearing aid fittings) was calculated. Three speech stimuli, (/m/, /t/, and /g/) were presented aided (monaurally, nontest ear occluded), free field, under three conditions (+4 dB/octave, -4 dB/octave, and without filtering), at levels of 40, 50, and 60 dB SPL (measured for the unfiltered condition). Behavioral thresholds were obtained, and CAEP recordings were made using these stimuli. The interaction of hearing loss, presentation levels, and filtering conditions resulted in a range of CAEP test behavioral sensation levels (SLs), from -25 to +40 dB. RESULTS: Statistically significant CAEPs (p < .05) were obtained for virtually every presentation where the behavioral sensation level was >10 dB, and for only 5% of occasions when the sensation level was negative. In these ("false-positive") cases, the greatest (negative) sensation level at which a CAEP was judged to be present was -6 dB SL. CONCLUSIONS: CAEPs are a sensitive tool for directly evaluating the audibility of speech sounds, at least for adult listeners. CAEP evaluation was found to be more accurate than audibility predictions, based on threshold and hearing aid response measures.

The effect of better-ear glimpsing on spatial release from masking.

The current experiment investigated whether better-ear glimpsing can explain the spatial release achieved by normal-hearing adults when situations are high in informational masking. Both modeling and behavioral methods were used. The speech reception thresholds of 38 young adults were measured for co-located, spatially separated and two better-ear glimpsed conditions. In the better-ear glimpsed conditions the binaural signals were processed so that in each time-frequency segment, the signal with the better SNR (left or right ear) was presented diotically. To investigate the effect of widening auditory filters on better-ear glimpsing, adjacent frequency bands were combined in one of the better-ear glimpsing conditions. Twenty-two participants were tested with maskers high in informational masking, while 16 participants were tested with maskers lower in informational masking. The mean speech reception thresholds achieved in the glimpsed conditions were significantly worse than in the spatially separated condition. This suggests that better-ear glimpsing can explain some but not all of the observed spatial release from masking. The difference between performance in the spatially separated and glimpsed conditions was largest when informational masking was high, suggesting better-ear glimpsing may release energetic rather than informational masking. Reducing the number of frequency bands sampled had a small effect on performance.

The importance of interaural time differences and level differences in spatial release from masking.

Numerous studies have described improvements in speech understanding when interaural time differences (ITDs) and interaural level differences (ILDs) are present. The present study aimed to investigate whether either cue in isolation can elicit spatial release from masking (SRM) in a speech-on-speech masking paradigm with maskers positioned symmetrically around the listener. Twelve adults were tested using three presentations of the Listening in Spatialized Noise-Sentences Test, with each presentation modified to contain different interaural cues in the stimuli. Results suggest that ILDs provide a similar amount of SRM as ITDs and ILDs combined. ITDs alone provide significantly less benefit.

An algorithm that administers adaptive speech-in-noise testing to a specified reliability at selectable points on the psychometric function.

OBJECTIVE: To introduce and verify an algorithm designed to administer adaptive speech-in- noise testing to a specified reliability at selectable points on the psychometric function. DESIGN: Speech-in-noise performances were measured using BKB sentences presented in diffuse babble-noise, using morphemic scoring. Target of the algorithm was a test-retest standard deviation of 1.13 dB within the presentation of 32 sentences. Normal-hearing participants completed repeated measures using manual administration targeting 50% correct, and the automated procedure targeting 25%, 50%, and 75% correct. Aided hearing-impaired participants completed testing with the automated procedure targeting 25%, 50%, and 75% correct, repeating measurements at the 50% point three times. STUDY SAMPLE: Twelve normal-hearing and 63 hearing-impaired people who had English as first language. RESULTS: Relative to the manual procedure, the algorithm produced the same speech reception threshold in noise (p = 0.96) and lower test-retest reliability on normal-hearing listeners. Both groups obtained significantly different results at the three target points (p < 0.04) with observed reliability close to expected. Target accuracy was not reached within 32 sentences for 18% of measurements on hearing-impaired participants. CONCLUSIONS: The reliability of the algorithm was verified. A second test is recommended if the target variability is not reached during the first measurement.

NAL-NL2 empirical adjustments.

NAL-NL1, the first procedure from the National Acoustic Laboratories (NAL) for prescribing nonlinear gain, was a purely theoretically derived formula aimed at maximizing speech intelligibility for any input level of speech while keeping the overall loudness of speech at or below normal loudness. The formula was obtained through an optimization process in which speech intelligibility and loudness were predicted from selected models. Using updated models and applying some revisions to the derivation process, a theoretically derived NAL-NL2 formula was obtained in a similar way. Further adjustments, directed by empirical data collected in studies using NAL-NL1 as the baseline response, have been made to the theoretically derived formula. Specifically, empirical data have demonstrated that (a) female hearing aid users prefer lower overall gain than male users; (b) new hearing aid users with more than a mild hearing loss prefer increasingly less gain with increasing degree of hearing loss than experienced hearing aid users, and require up to 2 years to adapt to gain levels selected by experienced hearing aid users; (c) unilaterally and bilaterally fitted hearing aid users prefer overall gain levels that vary less than estimated by the bilateral correction factor; (d) adults prefer lower overall gain than children; and (e) people with severe/profound hearing loss prefer lower compression ratios than predicted when fitted with fast-acting compression. The literature and data leading to these conclusions are summarized and discussed in this article, and the procedure for implementing the adjustments to the theoretically derived NAL-NL2 formula is described.

The relationship between cortical auditory evoked potential (CAEP) detection and estimated audibility in infants with sensorineural hearing loss.

OBJECTIVE: To determine the effectiveness of objective statistical detection in CAEP testing to evaluate audibility in young infants with sensorineural hearing loss. DESIGN: CAEP recordings to speech-based stimuli were made at three presentation levels (55, 65, or 75 dB SPL) when a group of hearing-impaired infants were either aided or unaided. Later-obtained behavioral audiograms were used as the gold standard against which to evaluate the accuracy of the automatic detection of the presence/absence of CAEP responses. STUDY SAMPLE: Participants were 18 infants with confirmed sensorineural hearing loss. RESULTS: Higher sensation levels led to a greater number of present CAEP responses being detected. More CAEP waveforms were detected in the aided condition than in the unaided condition. CONCLUSION: Our results suggest that the presence/absence of CAEP responses defined by the automatic statistical criterion was effective in showing whether increased sensation levels provided by amplification were sufficient to reach the cortex. This was clearly apparent from the significant increase in cortical detections when comparing unaided with aided testing.

Spatial release from masking in normal-hearing children and children who use hearing aids.

Listening to speech in competing sounds poses a major difficulty for children with impaired hearing. This study aimed to determine the ability of children (3-12 yr of age) to use spatial separation between target speech and competing babble to improve speech intelligibility. Fifty-eight children (31 with normal hearing and 27 with impaired hearing who use bilateral hearing aids) were assessed by word and sentence material. Speech reception thresholds (SRTs) were measured with speech presented from 0° azimuth, and competing babble from either 0° or ±90° azimuth. Spatial release from masking (SRM) was defined as the difference between SRTs measured with co-located speech and babble and SRTs measured with spatially separated speech and babble. On average, hearing-impaired children attained near-normal performance when speech and babble originated from the frontal source, but performed poorer than their normal-hearing peers when babble was spatially separated from target speech. On average, normal-hearing children obtained an SRM of 3 dB whereas children with hearing loss did not demonstrate SRM. Results suggest that hearing-impaired children may need enhancement in signal-to-noise ratio to hear speech in difficult listening conditions as well as normal-hearing children.

Listening in Spatialized Noise-Sentences Test (LiSN-S): normative and retest reliability data for adolescents and adults up to 60 years of age.

BACKGROUND: The Australian version of the Listening in Spatialized Noise-Sentences Test (LiSN-S) was originally developed to assess auditory stream segregation skills in children aged 6 to 11 yr with suspected central auditory processing disorder. The LiSN-S creates a three-dimensional auditory environment under headphones. A simple repetition-response protocol is used to assess a listener's speech reception threshold (SRT) for target sentences presented in competing speech maskers. Performance is measured as the improvement in SRT in decibels gained when either pitch, spatial, or both pitch and spatial cues are incorporated in the maskers. PURPOSE: To collect additional normative data on the Australian LiSN-S for adolescents and adults up to 60 yr of age, to analyze the effects of age on LiSN-S performance, to examine retest reliability in the older population, and to extrapolate findings from the Australian data so that the North American version of the test can also be used clinically with older adults. RESEARCH DESIGN: In a descriptive design, normative and test-retest reliability data were collected from adolescents and adults and combined with previously published data from Australian children aged 6 to 11 yr. STUDY SAMPLE: One hundred thirty-two participants with normal hearing aged 12 yr, 0 mo, to 60 yr, 7 mo, took part in the normative data study. Fifty-five participants returned between 2 and 4 mo after the initial assessment for retesting. RESULTS: Analysis of variance revealed a significant effect of age on LiSN-S performance (p < .01 for all LiSN-S measures, ηp2 ranging from 0.16 to 0.54). On the low and high cue SRT measures, planned contrasts revealed significant differences between adults and children aged 13 yr and younger, as well as between 50- to 60-yr-olds and younger adults aged 18-29 yr. Whereas there were significant differences between adults and children on the talker, spatial, and total advantage measures, there were no significant differences in performance in adults aged 18-60 yr. There was a small but significant improvement on retest ranging from 0.5 to 1.2 dB across the four LiSN-S test conditions (p ranging from .01 to <.001). However, there was no significant difference between test and retest on the advantage measures (p ranging from .143 to .768). Test-retest differences across all LiSN-S measures were significantly correlated (r ranging from 0.2 to 0.7, p ranging from .023 to <.00000001) and did not differ as a function of age (p ranging from .178 to .980). CONCLUSIONS: As there was no significant difference among adults aged 18-60 yr on the LiSN-S talker, spatial, and total advantage measures, it appears that the decline in ability to understand speech in noise experienced by 50- to 60-yr-olds is not related to their ability to use either spatial or pitch cues. This result suggests that some other factor/s contributes to the decline in speech perception in noise experienced by older adults that is reported in the literature and was demonstrated in this study on the LiSN-S low and high cue SRT measures.