Paired comparisons of nonlinear frequency compression, extended bandwidth, and restricted bandwidth hearing aid processing for children and adults with hearing loss.

BACKGROUND: Preference for speech and music processed with nonlinear frequency compression (NFC) and two controls (restricted bandwidth [RBW] and extended bandwidth [EBW] hearing aid processing) was examined in adults and children with hearing loss. PURPOSE: The purpose of this study was to determine if stimulus type (music, sentences), age (children, adults), and degree of hearing loss influence listener preference for NFC, RBW, and EBW. RESEARCH DESIGN: Design was a within-participant, quasi-experimental study. Using a round-robin procedure, participants listened to amplified stimuli that were (1) frequency lowered using NFC, (2) low-pass filtered at 5 kHz to simulate the RBW of conventional hearing aid processing, or (3) low-pass filtered at 11 kHz to simulate EBW amplification. The examiner and participants were blinded to the type of processing. Using a two-alternative forced-choice task, participants selected the preferred music or sentence passage. STUDY SAMPLE: Participants included 16 children (ages 8-16 yr) and 16 adults (ages 19-65 yr) with mild to severe sensorineural hearing loss. INTERVENTION: All participants listened to speech and music processed using a hearing aid simulator fit to the Desired Sensation Level algorithm v5.0a. RESULTS: Children and adults did not differ in their preferences. For speech, participants preferred EBW to both NFC and RBW. Participants also preferred NFC to RBW. Preference was not related to the degree of hearing loss. For music, listeners did not show a preference. However, participants with greater hearing loss preferred NFC to RBW more than participants with less hearing loss. Conversely, participants with greater hearing loss were less likely to prefer EBW to RBW. CONCLUSIONS: Both age groups preferred access to high-frequency sounds, as demonstrated by their preference for either the EBW or NFC conditions over the RBW condition. Preference for EBW can be limited for those with greater degrees of hearing loss, but participants with greater hearing loss may be more likely to prefer NFC. Further investigation using participants with more severe hearing loss may be warranted.

Effects of frequency compression and frequency transposition on fricative and affricate perception in listeners with normal hearing and mild to moderate hearing loss.

OBJECTIVES: The authors have demonstrated that the limited bandwidth associated with conventional hearing aid amplification prevents useful high-frequency speech information from being transmitted. The purpose of this study was to examine the efficacy of two popular frequency-lowering algorithms and one novel algorithm (spectral envelope decimation) in adults with mild to moderate sensorineural hearing loss and in normal-hearing controls. DESIGN: Participants listened monaurally through headphones to recordings of nine fricatives and affricates spoken by three women in a vowel-consonant context. Stimuli were mixed with speech-shaped noise at 10 dB SNR and recorded through a Widex Inteo IN-9 and a Phonak Naída UP V behind-the-ear (BTE) hearing aid. Frequency transposition (FT) is used in the Inteo and nonlinear frequency compression (NFC) used in the Naída. Both devices were programmed to lower frequencies above 4 kHz, but neither device could lower frequencies above 6 to 7 kHz. Each device was tested under four conditions: frequency lowering deactivated (FT-off and NFC-off), frequency lowering activated (FT and NFC), wideband (WB), and a fourth condition unique to each hearing aid. The WB condition was constructed by mixing recordings from the first condition with high-pass filtered versions of the source stimuli. For the Inteo, the fourth condition consisted of recordings made with the same settings as the first, but with the noise-reduction feature activated (FT-off). For the Naída, the fourth condition was the same as the first condition except that source stimuli were preprocessed by a novel frequency compression algorithm, spectral envelope decimation (SED), designed in MATLAB, which allowed for a more complete lowering of the 4 to 10 kHz input band. A follow-up experiment with NFC used Phonak's Naída SP V BTE, which could also lower a greater range of input frequencies. RESULTS: For normal-hearing and hearing-impaired listeners, performance with FT was significantly worse compared with that in the other conditions. Consistent with previous findings, performance for the hearing-impaired listeners in the WB condition was significantly better than in the FT-off condition. In addition, performance in the SED and WB conditions were both significantly better than in the NFC-off condition and the NFC condition with 6 kHz input bandwidth. There were no significant differences between SED and WB, indicating that improvements in fricative identification obtained by increasing bandwidth can also be obtained using this form of frequency compression. Significant differences between most conditions could be largely attributed to an increase or decrease in confusions for the phonemes /s/ and /z/. In the follow-up experiment, performance in the NFC condition with 10 kHz input bandwidth was significantly better than NFC-off, replicating the results obtained with SED. Furthermore, listeners who performed poorly with NFC-off tended to show the most improvement with NFC. CONCLUSIONS: Improvements in the identification of stimuli chosen to be sensitive to the effects of frequency lowering have been demonstrated using two forms of frequency compression (NFC and SED) in individuals with mild to moderate high-frequency sensorineural hearing loss. However, negative results caution against using FT for this population. Results also indicate that the advantage of an extended bandwidth as reported here and elsewhere applies to the input bandwidth for frequency compression (NFC/SED) when the start frequency is ≥4 kHz.

The influence of audibility on speech recognition with nonlinear frequency compression for children and adults with hearing loss.

OBJECTIVE: The primary goal of nonlinear frequency compression (NFC) and other frequency-lowering strategies is to increase the audibility of high-frequency sounds that are not otherwise audible with conventional hearing aid (HA) processing due to the degree of hearing loss, limited HA bandwidth, or a combination of both factors. The aim of the present study was to compare estimates of speech audibility processed by NFC with improvements in speech recognition for a group of children and adults with high-frequency hearing loss. DESIGN: Monosyllabic word recognition was measured in noise for 24 adults and 12 children with mild to severe sensorineural hearing loss. Stimuli were amplified based on each listener's audiogram with conventional processing (CP) with amplitude compression or with NFC and presented under headphones using a software-based HA simulator. A modification of the speech intelligibility index (SII) was used to estimate audibility of information in frequency-lowered bands. The mean improvement in SII was compared with the mean improvement in speech recognition. RESULTS: All but 2 listeners experienced improvements in speech recognition with NFC compared with CP, consistent with the small increase in audibility that was estimated using the modification of the SII. Children and adults had similar improvements in speech recognition with NFC. CONCLUSION: Word recognition with NFC was higher than CP for children and adults with mild to severe hearing loss. The average improvement in speech recognition with NFC (7%) was consistent with the modified SII, which indicated that listeners experienced an increase in audibility with NFC compared with CP. Further studies are necessary to determine whether changes in audibility with NFC are related to speech recognition with NFC for listeners with greater degrees of hearing loss, with a greater variety of compression settings, and using auditory training.

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.

Maximizing audibility and speech recognition with nonlinear frequency compression by estimating audible bandwidth.

OBJECTIVE: Nonlinear frequency compression attempts to restore high-frequency audibility by lowering high-frequency input signals. Methods of determining the optimal parameters that maximize speech understanding have not been evaluated. The effect of maximizing the audible bandwidth on speech recognition for a group of listeners with normal hearing is described. DESIGN: Nonword recognition was measured with 20 normal-hearing adults. Three audiograms with different high-frequency thresholds were used to create conditions with varying high-frequency audibility. Bandwidth was manipulated using three conditions for each audiogram: conventional processing, the manufacturer's default compression parameters, and compression parameters that optimized bandwidth. RESULTS: Nonlinear frequency compression optimized to provide the widest audible bandwidth improved nonword recognition compared with both conventional processing and the default parameters. CONCLUSIONS: These results showed that using the widest audible bandwidth maximized speech identification when using nonlinear frequency compression. Future studies should apply these methods to listeners with hearing loss to demonstrate efficacy in clinical populations.

Effects of reverberation on speech recognition in stationary and modulated noise by school-aged children and young adults.

OBJECTIVES: The purpose of this study was to determine how combinations of reverberation and noise, typical of environments in many elementary school classrooms, affect normal-hearing school-aged children's speech recognition in stationary and amplitude-modulated noise, and to compare their performance with that of normal-hearing young adults. In addition, the magnitude of release from masking in the modulated noise relative to that in stationary noise was compared across age groups in nonreverberant and reverberant listening conditions. Last, for all noise and reverberation combinations the degree of change in predicted performance at 70% correct was obtained for all age groups using a best-fit cubic polynomial. DESIGN: Bamford-Kowal-Bench sentences and noise were convolved with binaural room impulse responses representing nonreverberant and reverberant environments to create test materials representative of both audiology clinics and school classroom environments. Speech recognition of 48 school-aged children and 12 adults was measured in speech-shaped and amplitude-modulated speech-shaped noise, in the following three virtual listening environments: nonreverberant, reverberant at 2 m, and reverberant at 6 m. RESULTS: Speech recognition decreased in the reverberant conditions and with decreasing age. Release from masking in modulated noise relative to stationary noise decreased with age and was reduced by reverberation. In the nonreverberant condition, participants showed similar amounts of masking release across ages. The slopes of performance-intensity functions increased with age, with the exception of the nonreverberant modulated masker condition. The slopes were steeper in the stationary masker conditions, where they also decreased with reverberation and distance. In the presence of a modulated masker, the slopes did not differ between the two reverberant conditions. CONCLUSIONS: The results of this study reveal systematic developmental changes in speech recognition in noisy and reverberant environments for elementary-school-aged children. The overall pattern suggests that younger children require better acoustic conditions to achieve sentence recognition equivalent to their older peers and adults. In addition, this is the first study to report a reduction of masking release in children as a result of reverberation. Results support the importance of minimizing noise and reverberation in classrooms, and highlight the need to incorporate noise and reverberation into audiological speech-recognition testing to improve predictions of performance in the real world.

Audibility-based predictions of speech recognition for children and adults with normal hearing.

This study investigated the relationship between audibility and predictions of speech recognition for children and adults with normal hearing. The Speech Intelligibility Index (SII) is used to quantify the audibility of speech signals and can be applied to transfer functions to predict speech recognition scores. Although the SII is used clinically with children, relatively few studies have evaluated SII predictions of children's speech recognition directly. Children have required more audibility than adults to reach maximum levels of speech understanding in previous studies. Furthermore, children may require greater bandwidth than adults for optimal speech understanding, which could influence frequency-importance functions used to calculate the SII. Speech recognition was measured for 116 children and 19 adults with normal hearing. Stimulus bandwidth and background noise level were varied systematically in order to evaluate speech recognition as predicted by the SII and derive frequency-importance functions for children and adults. Results suggested that children required greater audibility to reach the same level of speech understanding as adults. However, differences in performance between adults and children did not vary across frequency bands.

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.

Performance-intensity functions for normal-hearing adults and children using computer-aided speech perception assessment.

OBJECTIVES: The Computer-Aided Speech Perception Assessment (CASPA) is a clinical measure of speech recognition that uses 10-item, isophonemic word lists to derive performance intensity (PI) functions for adult listeners. Because CASPA was developed for adults, the ability to obtain PI functions in children has not been evaluated directly. This study sought to evaluate PI functions for adults and four age groups of children with normal hearing to compare speech recognition as a function of age using CASPA. Comparisons between age groups for scoring by words and phonemes correct were made to determine the relative benefits of available scoring methods in CASPA. DESIGN: Speech recognition using CASPA was completed with 12 adults and four age groups of children (5- to 6-, 7- to 8-, 9- to 10-, and 11- to 12-yr olds), each with 12 participants. Results were scored by the percentage of words, phonemes, consonants, and vowels correct. All participants had normal hearing and age-appropriate speech production skills. RESULTS: Differences in speech recognition were significant across all age groups when responses were scored by the percentage of words correct. However, only differences between adults and the two youngest groups of children were significant when results were scored by the number of phonemes correct. Speech recognition scores decreased as a function of signal to noise ratio for both children and adults. However, the magnitude of degradation at poorer signal to noise ratios did not vary between adults and children, suggesting that mean differences could not be explained by interference from noise. CONCLUSIONS: Obtaining PI functions in noise using CASPA is feasible with children as young as 5 yrs. Statistically significant differences in speech recognition were observed between adults and the two youngest age groups of children when scored by the percentage of words correct. When results were scored by the percentage of phonemes correct, however, the only significant difference was between the youngest group of children and the adults. These results suggest that phoneme scoring may help to minimize differences between recognition scores of adults and children because children may be more likely to provide responses that are phonemic approximations when words are outside their lexicon.

Comparison of in-situ calibration methods for quantifying input to the middle ear.

Sound pressure level in-situ measurements are sensitive to standing-wave pressure minima and have the potential to result in over-amplification with risk to residual hearing in hearing-aid fittings. Forward pressure level (FPL) quantifies the pressure traveling toward the tympanic membrane and may be a potential solution as it is insensitive to ear-canal pressure minima. Derivation of FPL is dependent on a Thevenin-equivalent source calibration technique yielding source pressure and impedance. This technique is found to accurately decompose cavity pressure into incident and reflected components in both a hard-walled test cavity and in the human ear canal through the derivation of a second sound-level measure termed integrated pressure level (IPL). IPL is quantified by the sum of incident and reflected pressure amplitudes. FPL and IPL were both investigated as measures of sound-level entering the middle ear. FPL may be a better measure of middle-ear input because IPL is more dependent on middle-ear reflectance and ear-canal conductance. The use of FPL in hearing-aid applications is expected to provide an accurate means of quantifying high-frequency amplification.

Use of forward pressure level to minimize the influence of acoustic standing waves during probe-microphone hearing-aid verification.

Probe-microphone measurements are a reliable method of verifying hearing-aid sound pressure level (SPL) in the ear canal for frequencies between 0.25 and 4 kHz. However, standing waves in the ear canal reduce the accuracy of these measurements above 4 kHz. Recent data suggest that speech information at frequencies up to 10 kHz may enhance speech perception, particularly for children. Incident and reflected components of a stimulus in the ear canal can be separated, allowing the use of forward (incident) pressure as a measure of stimulus level. Two experiments were conducted to determine if hearing-aid output in forward pressure provides valid estimates of in-situ sound level in the ear canal. In experiment 1, SPL measurements were obtained at the tympanic membrane and the medial end of an earmold in ten adults. While within-subject test-retest reliability was acceptable, measures near the tympanic membrane reduced the influence of standing waves for two of the ten participants. In experiment 2, forward pressure measurements were found to be unaffected by standing waves in the ear canal for frequencies up to 10 kHz. Implications for clinical assessment of amplification are discussed.

Effects of stimulus bandwidth on the imitation of ish fricatives by normal-hearing children.

PURPOSE: Recent studies from the authors' laboratory have suggested that reduced audibility in the high frequencies (because of the bandwidth of hearing instruments) may play a role in the delays in phonological development often exhibited by children with hearing impairment. The goal of the current study was to extend previous findings on the effect of bandwidth on fricatives/affricates to more complex stimuli. METHOD: Nine fricatives/affricates embedded in 2-syllable nonsense words were filtered at 5 and 10 kHz and presented to normal-hearing 6- to 7-year-olds who repeated words exactly as heard. Responses were recorded for subsequent phonetic and acoustic analyses. RESULTS: Significant effects of talker gender and bandwidth were found, with better performance for the male talker and the wider bandwidth condition. In contrast to previous studies, relatively small (5%) mean bandwidth effects were observed for /s/ and /z/ spoken by the female talker. Acoustic analyses of stimuli used in the previous and the current studies failed to explain this discrepancy. CONCLUSIONS: It appears likely that a combination of factors (i.e., dynamic cues, prior phonotactic knowledge, and perhaps other unidentified cues to fricative identity) may have facilitated the perception of these complex nonsense words in the current study.

Effect of stimulus bandwidth on auditory skills in normal-hearing and hearing-impaired children.

OBJECTIVE: Previous studies from our laboratory have shown that a restricted stimulus bandwidth can have a negative effect upon the perception of the phonemes /s/ and /z/, which serve multiple linguistic functions in the English language. These findings may have important implications for the development of speech and language in young children with hearing loss because the bandwidth of current hearing aids generally is restricted to 6 to 7 kHz. The primary goal of the current study was to expand our previous work to examine the effects of stimulus bandwidth on a wide range of speech materials, to include a variety of auditory-related tasks, and to include the effects of background noise. DESIGN: Thirty-two children with normal hearing and 24 children with sensorineural hearing loss (7 to 14 yr) participated in this study. To assess the effects of stimulus bandwidth, four different auditory tasks were used: 1) nonsense syllable perception, 2) word recognition, 3) novel-word learning, and 4) listening effort. Auditory stimuli recorded by a female talker were low-pass filtered at 5 and 10 kHz and presented in noise. RESULTS: For the children with normal hearing, significant bandwidth effects were observed for the perception of nonsense syllables and for words but not for novel-word learning or listening effort. In the 10-kHz bandwidth condition, children with hearing loss showed significant improvements for monosyllabic words but not for nonsense syllables, novel-word learning, or listening effort. Further examination, however, revealed marked improvements for the perception of specific phonemes. For example, bandwidth effects for the perception of /s/ and /z/ were not only significant but much greater than that seen in the group with normal hearing. CONCLUSIONS: The current results are consistent with previous studies that have shown that a restricted stimulus bandwidth can negatively affect the perception of /s/ and /z/ spoken by female talkers. Given the importance of these phonemes in the English language and the tendency of early caregivers to be female, an inability to perceive these sounds correctly may have a negative impact on both phonological and morphological development.

The importance of high-frequency audibility in the speech and language development of children with hearing loss.

OBJECTIVES: To review recent research studies concerning the importance of high-frequency amplification for speech perception in adults and children with hearing loss and to provide preliminary data on the phonological development of normal-hearing and hearing-impaired infants. DESIGN AND SETTING: With the exception of preliminary data from a longitudinal study of phonological development, all of the reviewed studies were taken from the archival literature. To determine the course of phonological development in the first 4 years of life, the following 3 groups of children were recruited: 20 normal-hearing children, 12 hearing-impaired children identified and aided up to 12 months of age (early-ID group), and 4 hearing-impaired children identified after 12 months of age (late-ID group). Children were videotaped in 30-minute sessions at 6- to 8-week intervals from 4 to 36 months of age (or shortly after identification of hearing loss) and at 2- and 6-month intervals thereafter. Broad transcription of child vocalizations, babble, and words was conducted using the International Phonetic Alphabet. A phoneme was judged acquired if it was produced 3 times in a 30-minute session. SUBJECTS: Preliminary data are presented from the 20 normal-hearing children, 3 children from the early-ID group, and 2 children from the late-ID group. RESULTS: Compared with the normal-hearing group, the 3 children from the early-ID group showed marked delays in the acquisition of all phonemes. The delay was shortest for vowels and longest for fricatives. Delays for the 2 children from the late-ID group were substantially longer. CONCLUSIONS: The reviewed studies and preliminary results from our longitudinal study suggest that (1) hearing-aid studies with adult subjects should not be used to predict speech and language performance in infants and young children; (2) the bandwidth of current behind-the-ear hearing aids is inadequate to accurately represent the high-frequency sounds of speech, particularly for female speakers; and (3) preliminary data on phonological development in infants with hearing loss suggest that the greatest delays occur for fricatives, consistent with predictions based on hearing-aid bandwidth.

Novel-word learning in children with normal hearing and hearing loss.

OBJECTIVE: The goal of this study was to assess performance on a novel-word learning task by normal-hearing and hearing-impaired children for words varying in form (noun versus verb), stimulus level (50 versus 60 dB SPL), and number of repetitions (4 versus 6). It was hypothesized that novel-word learning would be significantly poorer in the subjects with hearing loss, would increase with both level and repetition, and would be better for nouns than verbs. DESIGN: Twenty normal-hearing and 11 hearing-impaired children (6 to 9 yr old) participated in this study. Each child viewed a 4-minute animated slide show containing 8 novel words. The effects of hearing status, word form, repetition, and stimulus level were examined systematically. The influence of audibility, word recognition, chronological age, and lexical development also were evaluated. After hearing the story twice, children were asked to identify each word from a set of four pictures. RESULTS: Overall performance was 60% for the normal-hearing children and 41% for the children with hearing loss. Significant predictors of performance were PPVT raw scores, hearing status, stimulus level, and repetitions. The variables age, audibility, word recognition scores, and word form were not significant predictors. CONCLUSIONS: Results suggest that a child's ability to learn new words can be predicted from vocabulary size, stimulus level, number of exposures, and hearing status. Further, the sensitivity to presentation level observed in this novel-word learning task suggests that this type of paradigm may be an effective tool for studying various forms of hearing aid signal processing algorithms.

Spectral characteristics of speech at the ear: implications for amplification in children.

This study examined the long- and short-term spectral characteristics of speech simultaneously recorded at the ear and at a reference microphone position (30 cm at 0 degrees azimuth). Twenty adults and 26 children (2-4 years of age) with normal hearing were asked to produce 9 short sentences in a quiet environment. Long-term average speech spectra (LTASS) were calculated for the concatenated sentences, and short-term spectra were calculated for selected phonemes within the sentences (/m/, /n/, /s/, [see text], /f/, /a/, /u/, and /i/). Relative to the reference microphone position, the LTASS at the ear showed higher amplitudes for frequencies below 1 kHz and lower amplitudes for frequencies above 2 kHz for both groups. At both microphone positions, the short-term spectra of the children's phonemes revealed reduced amplitudes for /s/ and [see text] and for vowel energy above 2 kHz relative to the adults' phonemes. The results of this study suggest that, for listeners with hearing loss (a) the talker's own voice through a hearing instrument would contain lower overall energy at frequencies above 2 kHz relative to speech originating in front of the talker, (b) a child's own speech would contain even lower energy above 2 kHz because of adult-child differences in overall amplitude, and (c) frequency regions important to normal speech development (e.g., high-frequency energy in the phonemes /s/ and [see text]) may not be amplified sufficiently by many hearing instruments.

Aided perception of /s/ and /z/ by hearing-impaired children.

OBJECTIVE: The overall goal of this study was to determine the accuracy with which hearing-impaired children can detect the inflectional morphemes /s/ and /z/ when listening to speech through hearing aids. DESIGN: In the first part of the study a perceptual test was developed with equal numbers of singular and plural nouns spoken by both a male and female talker. Thirty-six normal-hearing children (3 to 5 yr) were tested to determine the age at which children could perform this test without difficulty. In the second part of the study, 40 children with bilateral sensorineural hearing losses (5 to 13 yr) were tested while wearing personal hearing aids. Stimuli were presented in the sound field at 65 dB SPL. RESULTS: For the normal-hearing children, mean performance increased and inter-subject variability decreased through age 5 yr 3 mo when performance reached >or=90% for all children. No significant talker or form (plural versus singular) effects were noted for this group. For the hearing-impaired children, performance varied considerably across all ages. For these subjects, significant effects of talker and form were observed. Specifically, plural test items spoken by the female talker showed the highest error rate. CONCLUSIONS: In general, mid-frequency audibility (2 to 4 kHz) appeared to be most important for perception of the fricative noise for the male talker while a somewhat wider frequency range (2 to 8 kHz) was important for the female talker.

Influence of hearing loss on the perceptual strategies of children and adults.

To accommodate growing vocabularies, young children are thought to modify their perceptual weights as they gain experience with speech and language. The purpose of the present study was to determine whether the perceptual weights of children and adults with hearing loss differ from those of their normal-hearing counterparts. Adults and children with normal hearing and with hearing loss served as participants. Fricative and vowel segments within consonant-vowel-consonant stimuli were presented at randomly selected levels under two conditions: unaltered and with the formant transition removed. Overall performance for each group was calculated as a function of segment level. Perceptual weights were also calculated for each group using point-biserial correlation coefficients that relate the level of each segment to performance. Results revealed child-adult differences in overall performance and also revealed an effect of hearing loss. Despite these performance differences, the pattern of perceptual weights was similar across all four groups for most conditions.