Maximum length sequences-auditory brainstem responses from children with auditory processing disorders.

This study was designed to evaluate maximum length sequences-auditory brainstem responses (MLS-ABR) in children with auditory processing disorders and to compare these results with a normal control group matched for age, intelligence, and gender. Although each waveform was analyzed for the presence of waves I, III, and V, the primary focus was wave V. Although absolute latency measures for wave V were obtained from all subjects, waves I and III were not always identified. Although the results showed latency increases for all waveforms in both groups, the only significant difference noted was an increase in wave V latency for both the left and right ears in the clinical group. These results suggest that the MLS-ABR may be useful in the assessment of auditory processing disorders. Implications for the potential use of the MLS-ABR in management programs are discussed.

The clinical utility of the P3 AERP in children with auditory processing disorders.

This study investigated whether the P3 AERP could be used to reflect behavioral changes resulting from therapeutic intervention in a group of children with central auditory processing disorders (CAPDs). Results showed a significant decrease in P3 latency, along with a significant increase in P3 amplitude, following a structured treatment program. No changes occurred in either the CAPD control group or in the normal control group. These results suggest that the P3 AERP latency and amplitude measures are sensitive to changes in clinical status following a treatment program.

Long latency auditory event-related potentials from children with auditory processing disorders.

The purpose of this study was to evaluate auditory event-related potentials, and related long latency components, in children with auditory processing disorders, and to compare these results with a normal group matched for age, intelligence, and gender. Results showed a significant latency increase for the N1, P2, and P3 components in the processing disordered group. Furthermore, the interpeak latency interval P2-P3 was significantly longer in the clinical group. In terms of amplitude measures, only P3 amplitude differed significantly between groups. These results suggest that the long latency potentials may be useful in the assessment of children with processing disorders.

Effects of intermodulation distortion on speech intelligibility.

This investigation was designed (1) to investigate further intermodulation distortion in hearing aids, and (2) to determine the effect of this type of distortion on speech intelligibility. After four hearing aids were analyzed for intermodulation distortion, 10 CID sentences were recorded through each instrument and presented to both normally hearing and sensorineurally impaired listeners. Results indicated an inverse relationship between levels of intermodulation distortion and frequency, with the highest distortion levels found below 1 kHz. This low-frequency distortion significantly interfered with speech intelligibility for sensorineurally impaired subjects listening to sentences in quite. For both the normally hearing group and the sensorineural group listening in noise, no significant differences were found. The results were interpreted to suggest that the low-frequency intermodulation distortion resulted in an upward spread of masking which interfered with perception of high-frequency acoustic cues in sensorineural impaired listeners; however, with the addition of a competing signal, the subtle masking effect of intermodulation distortion were obscured. Implications for additional research are discussed.

Relationship of acoustic gain to aided threshold improvement in children.

Aided threshold improvement obtained by 12 hearing-impaired children was compared to the acoustic gain of their hearing aids using both the traditional 2-cc coupler and a variable volume coupler designed to approximate real ear volume in children. Results indicated that acoustic gain determined in the 2-cc coupler underestimated aided threshold improvement by approximately 8.7 dB. Use of the variable volume coupler to determine acoustic gain, however, adequately predicted aided improvement at comfort setting. Use of the variable volume coupler in hearing-aid fittings for children is discussed with special emphasis on preventing over-amplification.

A critical examination of distortion measurement in hearing aids.

This study was designed to examine relationships between measures of total distortion (TD) and individual 2nd and 3rd harmonic distortion in various types of hearing aids. Measures of 2nd harmonic, 3rd harmonic, and TD were determined for six instruments. Analysis of the results revealed that little additional information is obtained from a measure of TD as opposed to individual harmonic measures. Furthermore, in two instances TD measures resulted in erroneously high distortion readings because of ambient and system noise. It is recommended that in less than ideal acoustic environments, measures of 2nd and 3rd harmonic distortion be used in lieu of TD.

Lack of reliability of the SISI procedure for determining inner ear threshold.

Ten normally hearing subjects were tested using the conductive short increment sensitivity index procedure to evaluate the 60-dB constant as used in the test described by Byers (1974). Also investigated were the effects of frequency and order of presentation on the short increment sensitivity index at high sensation levels. Test frequencies included 1, 2, 4, and 6 kHz in random order. Means of all frequencies exceeded the 60-dB constant implemented by Byers (1974). Intersubject variability was large. Frequency and order of presentation were not statistically significant factors. It was recommended that the conductive short increment sensitivity index be used with caution.

Unreliability of half-list discrimination tests.

The present study was undertaken to investigate the reliability of the half-list forms of the CID W-22 and the NU no. 6 auditory discrimination tests with both normally hearing and sensorineurally impaired subjects. For each group of subjects, both the first half-lists and the whole-lists were scored. Analysis of the data indicated that the half-list forms of the tests were not as reliable as sometimes suggested in the literature. Further, the half-list form of the NU no. 6 was demonstrated to be not as reliable as the half-list form of the CID W-22 even before the correction coefficient was applied.