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Adaptation and the masking of tinnitus.

The effect of adaptation on the masking of tinnitus was investigated. Six patients with tinnitus performed two 5-min tracking tasks, each replicated six times. The first task examined the masking of tinnitus by tracking the intensity of a pure tone required to mask the tinnitus. The second task examined adaptation of a suprathreshold tone by tracking the intensity of a pure tone required for constant loudness. For 3 patients, the change required for constant loudness did not differ from the change required for constant maskability. For 3 patients, however, these two changes were different. Possible implications of these results for determining the locus of tinnitus and for the use of tinnitus maskers are discussed.

Adaptation, Physiological↗

Masking of tone bursts by modulated noise in normal, noise-masked normal, and hearing-impaired listeners.

Threshold of 4.6-ms tone bursts was measured in quiet and in the presence of a 100% sinusoidally amplitude-modulated speech-shaped noise. For the modulated-noise conditions, the onset of the tone burst coincided either with the maximum or the minimum modulator amplitude. The difference in these two masked thresholds provided an indication of the psychoacoustic modulation depth, or the modulation depth preserved within the auditory system. Modulation frequencies spanning the modulation spectrum of speech (2.5 to 20 Hz) were examined. Tone bursts were 500, 1400, and 4000 Hz. Subjects included normal listeners, normal listeners with a hearing loss simulated by high-pass noise, and hearing-impaired listeners having high-frequency sensorineural hearing loss. Normal listeners revealed a psychoacoustic modulation depth of 30-40 dB for the lowest modulation frequencies which decreased to about 15 dB at 20 Hz. The psychoacoustic modulation depth was decreased in the normal listeners with simulated hearing loss and in the hearing-impaired listeners. There was general agreement in the data, however, for the latter two groups of listeners suggesting that the normal listeners with hearing loss simulated by an additional masking noise provided a good representation of the performance of hearing-impaired listeners on this task.

Adult↗

Temporal effects in simultaneous masking by vowel and consonant-vowel maskers.

Temporal effects in simultaneous masking were studied using synthetic vowel (V) and consonant-vowel (CV) maskers. For the steady-state V maskers (/i,a,u/), signals were presented at the beginning or in the temporal center of the masker. The masking patterns generally reflected the formant differences among the vowels, and the formant structure of each V masker was more clearly revealed when the signal was presented in the temporal center of the masker. For the CV maskers (/bi,gi/), signals were presented at the beginning of the (consonant portion of the) masker, at the beginning of the vowel portion of the masker, or in the temporal center of the masker. The second-formant difference between the maskers (observed acoustically at their onset) was generally revealed in the masking patterns when the signal was presented at the beginning of the consonant; this difference in the masking patterns was also present, to a lesser extent, when the signal was presented at the beginning of the vowel, where the two maskers were identical acoustically. The masking patterns for the two CV maskers were virtually identical when the signal was presented in the temporal center of the masker. These data extend previous tone-on-tone masking data and suggest that the auditory system requires a certain amount of time to represent most accurately the acoustic spectrum of both steady-state and dynamic complex maskers.

Adult↗

Auditory temporal acuity in normally achieving and learning-disabled college students.

Recent research has suggested that deficits in several metalinguistic/phonological abilities, such as short-term verbal memory and phoneme segmentation, may be etiologic factors in specific reading disability, and it has been speculated that these weaknesses may result from a more fundamental deficit in the processing of temporal, auditory stimuli. This study examined the auditory temporal processing skills of reading-disabled, math-disabled, and normally achieving college students. The math-disabled group was included to control for the possibility that poor temporal processing is a "marker" variable for learning disability rather than being related specifically to reading disability. Subjects were assessed on a battery of psychophysical tasks that included five tests of temporal processing. The reading-disabled group performed significantly more poorly on the temporal tasks but performed as well as the other groups on the simple pitch and loudness discrimination tasks. In spite of the significant difference on the temporal tasks, the majority of reading-disabled subjects performed within the same range as the subjects in the other two groups, and there were also some normally reading subjects who performed poorly on the temporal processing tasks. These findings suggest that poor temporal processing is neither a necessary nor a sufficient cause of reading disability, but that there is a modest association between the two domains.

Achievement↗

The development and cross-validation of a self-report inventory to assess pure-tone threshold hearing sensitivity.

Previous attempts to assess hearing loss by means of self-report survey items have shown only low to moderate correlations with actual audiometric measures, probably because these attempts used items with high face validity rather than laboratory-tested validity. Beginning with a pool of 108 items used with 384 individuals, we developed a self-report inventory (see Appendix) suitable for group testing or survey administration, which appears to have high correlation with pure-tone hearing thresholds. The inventory was then cross-validated against laboratory audiometric measures in a separate sample of 422 subjects. The resulting 12-item Hearing Screening Inventory (HSI) was shown to be reliable with an internal consistency coefficient (alpha) of 0.89 and test-retest stability coefficient of 0.88. The correlation between pure-tone hearing thresholds in the better ear and the HSI scores for the combined samples was r = 0.81. The correct classification rate for the HSI was 92.1% for a low fence of 25-dB hearing level and 93.4% for a high fence of 55-dB hearing level. A conversion equation with estimated variability is also provided for point estimates of pure-tone hearing thresholds from the HSI scores. A copy of the inventory and scoring procedure is appended to this report.

Adult↗

Some psychometric properties of the Test of Basic Auditory Capabilities (TBAC).

This study examined some psychometric properties of the Test of Basic Auditory Capabilities (TBAC). Two experiments are described that evaluate the psychometric functions and the test-retest reliability of the tests comprising the TBAC. The psychometric functions were established for young listeners with normal hearing and the test-retest reliability was evaluated both with young listeners with normal hearing and elderly listeners with hearing impairment. Results indicate that maximum scores on the TBAC are reached at presentation levels of at least 65-75 dB SPL. In addition, the reliability analyses indicate that the TBAC is a reliable measure for both young listeners with normal hearing and elderly listeners with hearing impairment when at least one practice test is given.

Adult↗

Distortion-product emissions and auditory sensitivity in human ears with normal hearing and cochlear hearing loss.

Distortion product emissions (DPEs) at 2f1-f2 frequencies were measured in 53 human ears; 21 of them exhibited cochlear hearing loss. DPEs were obtained as a function of stimulus level (DPE growth curves) at seven frequency regions between 707 Hz and 5656 Hz. Several distinctly different shapes or patterns of DPE growth curves were observed. These included single-segment monotonic growth curves with and without saturation at moderate and high stimulus levels, diphasic growth curves with nulls at moderate stimulus levels, and non-monotonic growth curves with negative slopes at high stimulus levels. Low-level, irregularly shaped segments were more frequent in normal-hearing ears, suggestive of normal low-level active nonlinearities from the outer-hair-cell subsystem. High-level, steeply sloped segments were frequent in hearing-impaired ears, suggestive of residual nonlinearities from a cochlear partition without functional outer hair cells. The stimulus level at which the DPE could just be distinguished from the noise floor, the DPE detection threshold, demonstrated moderate positive correlations (r's from 0.50 to 0.81) with auditory thresholds when all ears, both normal and impaired, were considered together. Those correlations were not strong enough to quantitatively predict auditory thresholds with any great accuracy. However, DPE thresholds were able to predict abnormal auditory sensitivity with some precision. DPE thresholds correctly predicted abnormal auditory sensitivity 79% of the time in the present study, and up to 96% of the time in previous studies. These results suggest that DPE thresholds may prove useful for hearing screening in cases where cooperation from the subject is limited or where corroboration of cochlear hearing loss is required. Different patterns of DPE growth curves suggest underlying micro-mechanical differences between ears, but the differential diagnostic value of those patterns remains to be determined.

Acoustic Stimulation↗

Masking of tinnitus induced by sound.

Two experiments were performed in which 8 listeners used external sound to mask the tinnitus induced by a 95-dB SPL tone presented for 1 min. Wider bandwidth noises were more effective maskers than noises of critical bandwidth, which, in turn, were more effective than tonal maskers. Contralateral maskers were often effective, but less so than ipsilateral maskers. Tuning curves showed some degree of frequency specificity that was not related to the frequency of the tinnitus-inducing tone. There were consistent and pronounced differences between individual listeners. Overall, our results indicate both similarities and differences between the masking of induced tinnitus and the masking of pathological tinnitus.

Adult↗

Temporal analysis in children.

This study investigated the development of temporal resolution as a function of frequency region using a modified masking period pattern paradigm. This paradigm also allowed age-dependent comparisons of within-channel (temporal resolution) versus across-channel (comodulation masking release [CMR]) processing of temporal information to be made in the same listeners. The results indicated that temporal resolution improves with age. At low frequencies, this improvement continues beyond 10 years of age, whereas at high frequencies performance approaches adult levels by about age 6. Although it is reasonable to expect an association between CMR and temporal acuity, the measure of CMR did not show a significant age effect. The possibility was raised that the poorer temporal resolution of children may not reflect simply a deficiency in peripheral processing of temporal information.

Adult↗

Influence of frequency selectivity on comodulation masking release in normal-hearing listeners.

Experiments 1 and 2 investigated the effect of frequency selectivity on comodulation masking release (CMR) in normal-hearing subjects, examining conditions where frequency selectivity was relatively good (low masker level at both low [500-Hz] and high [2500-Hz] signal frequency, and high masker level at low signal frequency) and where frequency selectivity was somewhat degraded (high masker level and high signal frequency). The first experiment investigated CMR in conditions where a narrow modulated noise band was centered on the signal frequency, and a wider comodulated noise band was located below the band centered on the signal frequency. Signal frequencies were 500 and 2000 Hz. The masker level and the frequency separation between the on-signal and comodulated flanking band were varied. In addition to conditions where the flanking band and on-signal band were presented at the same spectrum level, conditions were included where the spectrum level of the flanking band was 10-dB higher than that of the on-signal band, in order to accentuate effects of reduced frequency selectivity. Results indicated that CMR was reduced at the 2000-Hz region when masker level was high, when the frequency separation between on-signal and flanking band was small, and when a 10-dB level disparity existed between the on-signal and flanking band. In the second experiment, CMR was investigated for narrow comodulated noise bands, presented either without any additional sound or in the presence of a random noise background. CMR increased slightly as the masker level increased, except at 2500 Hz when the noise background was present. The decrease in CMR at 2500 Hz with the high masker level and with a noise background present could be explained in terms of reduced frequency selectivity. In a third experiment, we compared performance for equal absolute bandwidth maskers at a low (500-Hz) and a high (2000-Hz) stimulus frequency. Results here suggested that detection in modulated noise may be reduced due to a reduction in the number of quasi-independent auditory filters contributing temporal envelope information. The effects found in the present study using normal-hearing listeners under conditions of degraded frequency selectivity may be useful in understanding part of the reduction of CMR that occurs in cochlear-impaired listeners having reduced frequency selectivity.

Auditory Perception↗

Psychometric functions for children's detection of tones in noise.

This article reports the results of an experiment that used a two-alternative forced-choice task to measure the ability of 3- to 5-year-old children to detect 501 Hz, 1000 Hz, and 2818 Hz sinusoids in noise. Psychometric functions were fit to each individual's data, and thresholds (signal level required for 75% correct) were interpolated from the fitted functions. Results showed that, on average, the children's thresholds were higher and the slopes of their psychometric functions were shallower than those of the adults. However, the between-subjects variability in the children's data was large, and the performance of many individual children was not well described by group mean performance. One-third of the children produced thresholds that were elevated by an average of 10 dB but psychometric function slopes that were adult-like. Another one-third of the children produced thresholds that were elevated relative to those of the adults by an average of 20 dB and psychometric function slopes that were very shallow. The data from a smaller group of children showed large variability in psychometric function slope and threshold, and for a very few children performance was at chance regardless of the signal level. A replication of the study several months later showed that for most listeners the individual patterns of performance persisted over time.

Acoustic Stimulation↗

Effect of step size on clinical and adaptive 2IFC procedures in quiet and in a noise background.

Audibility thresholds for a 1000-Hz sinusoid were measured with a standard clinical (CLIN) procedure and a two-interval, forced-choice (2IFC) adaptive procedure bracketing 79% correct. Both used 2- and 5-dB step sizes in quiet and in a continuous, broadband noise background. Clinical thresholds were from 2 to 4 dB higher than 2IFC thresholds, depending on the condition. Step size had a larger effect on the CLIN thresholds than the 2IFC thresholds. For the CLIN procedure, thresholds with a 2-dB step size were 1.4 dB lower than with a 5-dB step size. For the 2IFC procedure, thresholds with a 2-dB step size were 0.8 dB higher than with a 5-dB step size. Reliability, as measured by the intrasubject standard deviation, was better for the 2IFC than for the CLIN procedure and better in noise than in quiet. Reliability was unaffected by step size. Adding extra trials to the 2IFC adaptive track decreased the variability across threshold estimates, but more for the noise background than the quiet background. The efficiency of the 2IFC procedure was fairly constant across track length in noise, but decreased for longer track lengths in quiet. In both quiet and noise backgrounds, CLIN procedures were much more efficient than 2IFC procedures.

Adult↗

Multichannel compression, temporal cues, and audibility.

Although multichannel compression systems are quickly becoming integral components of programmable hearing aids, research results have not consistently demonstrated their benefit over conventional amplification. The present study examined two confounding factors that may have contributed to this inconsistency in results: alteration of temporal information and audibility of speech cues. Recognition of linearly amplified and multichannel-compressed speech was measured for listeners with mild-to-severe sensorineural hearing loss and for a control group of listeners with normal hearing. In addition to the standard speech signal, which provided both temporal and spectral information, the listener's ability to use temporal information in a multichannel compressed signal was directly tested using a signal-correlated noise (SCN) stimulus. This stimulus consisted of a time-varying speech envelope modulating a two-channel noise carrier. It preserved temporal cues but provided minimal spectral information. For each stimulus condition, short-term level measurements were used to determine the range of audible speech. Multichannel compression improved speech recognition under conditions where superior audibility was provided by the two-channel compression system over linear amplification. When audibility of both linearly amplified and multichannel-compressed speech was maximized, the multichannel compression had no significant effect on speech recognition score for speech containing both temporal and spectral cues. However, results for the SCN stimuli show that more extreme amounts of multichannel compression can reduce use of temporal information.

Adult↗

Peripheral auditory asymmetry in infantile autism.

Difficulty in filtering relevant auditory information in background noise is one of the features of autism. Auditory filtering processes can be investigated at the peripheral level as they are hypothesized to involve active cochlear mechanisms which are regulated by the efferent activity of the medial olivocochlear (MOC) system. The aim of the present work was therefore to assess these peripheral auditory processes in 22 children and adolescents with autism compared with age- and gender-matched normal controls. Active cochlear mechanisms were evaluated with transiently evoked otoacoustic emissions (TEOAEs) and MOC system efficiency was assessed via TEOAEs which are decreased when stimulating the contralateral ear with noise. The MOC system evaluation was performed on 18 of the 22 children. In both studies, results were analysed according to age (from 4 to 10 years and from 11 to 20 years). The main result concerns the asymmetry of the efferent system which differs in individuals with autism. Several neural processes might be hypothesized as involved in the results obtained as the MOC system which originates in the brainstem received regulating controls from upper brain structures including auditory cortex. Lateralization abnormalities at the auditory periphery may reflect indirectly a problem at a higher level of auditory processing. A second important result shows a decrease in TEOAE amplitude with age, in patients, that may correspond to a decrease in hearing sensitivity.

Adolescent↗

Auditory event-related potentials in the assessment of auditory processing disorders: a pilot study.

The aim of this pilot study was to investigate whether children with a suspected auditory processing disorder (sAPD) in the presence of normal hearing, differ significantly from normal age-matched controls on particular parameters of auditory event-related potentials. We assessed nine children (mean age 9.5 years) in whom the clinical profile and the results in a screening test for auditory processing disorder (SCAN/SCAN-A) suggested the presence of an auditory processing disorder, and nine age-matched normal control subjects, using auditory event-related potentials (ERP) to phonemes/ba/(standard) and/da/(deviant). Analysis of the auditory ERP recordings revealed an enlarged P85 - 120 and attenuated N1 and P2 in all sAPD children compared to controls. We also found significantly increased N1 peak latency, and a larger peak to peak amplitude of the P85 - 120-N1 and P2-N2 and smaller peak to peak amplitude of the N1-P2 in the sAPD children. Subtraction of the standard auditory ERP from the deviant revealed a mismatch negativity with no significant differences in duration, peak or onset latency between the control subjects and sAPD. Our results indicate that neurophysiological measures may identify a group of children with specific problems suggestive of an auditory processing disorder in the absence of an obvious structural or functional lesion who warrant further study in order to assess whether these findings reflect delayed CNS myelination.

Acoustic Stimulation↗

[Critical analysis of children with suspicion of auditory processing disorders].

BACKGROUND: APDs at infancy has become a common reason of introduction at phoniatric/pedaudiologic departments. The question arises whether this neurocognitive construct can be accounted with the standard clinical diagnostics. METHODS: The children with suspicion of APD referred to the Department of Phoniatrics/Pedaudiology at the University Hospital Goettingen/Germany were clinically examined. PATIENTS: Of 107 children 8 % demonstrated abnormal hearing acuity, 7 % learning and intelligence disorders, 7 % developmental dyslexia, 6 % language impairments, and 5 % attention deficit/hyperactivity. So, 59 children remained for evaluating for an APD (mean age: 85.3; SD 16.3 months). RESULTS: Their auditory performances were normdeviant from 7 % (speech audiometry) to 86 % (auditory sequential short-term memory for non-words). 55 % of the children exhibited a reduced dichotic word discrimination, 59 % a performance below norm level in auditory sequential memory for digits, and 86 % for non-words. Next step, the children of the study group were distributed according to their therapy situations at the time of examination: without; speech therapy; occupational therapy; speech therapy + occupational therapy. No significant group effects were found in the mean performances of the audiometric and psychometric tests, even though the results considerably differed. No auditory dimension made a contribution to separate the groups in a stepwise discriminant analysis. CONCLUSIONS: There was a notably inherent heterogeneity of the population presenting with auditory processing problems. The overall objective of the APD evaluation must be to assess processing skills apart from complex stimuli like language skills (e. g. parameter of tones, memory of tone pitch).

Attention Deficit Disorder with Hyperactivity↗

Auditory stimulus detection is not suppressed during saccadic eye movements.

Auditory detection and pitch discrimination thresholds were measured during saccades and during periods of fixation. The accuracy of auditory localisation under these two conditions was also measured. These thresholds were unaffected by whether the sound was presented during a saccade or during periods of steady fixation: there is no evidence for saccadic suppression of auditory processing.

Auditory Perception↗