ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Amplitude growth functions of the electrically elicited stapedius reflex were compared with behavioral estimates of dynamic range in seven patients using multielectrode cochlear implants. The range between threshold and saturation level of the amplitude growth function usually either encompassed or fell between the preferred and uncomfortable listening levels. Implications of these findings for the initial mapping of electrodes in young children are discussed.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The present study was designed to investigate whether mellaril and thorazine, when used alone and in combination with other medications by mentally retarded clients, either abolish acoustic reflexes or compromise estimates of hearing sensitivity based on acoustic reflex measures. Acoustic reflex thresholds were determined in 35 normal-hearing institutionalized mentally retarded subjects who were regular users of the medications under investigation. Five sensitivity prediction methods based on acoustic reflex thresholds were applied to the data. The results of the study showed that acoustic reflexes were present in most subjects. However, the accuracy of all the acoustic reflex-based sensitivity prediction methods was quite poor with greatly exaggerated predictions of hearing loss. The methods based solely on noise reflex thresholds provided better accuracy than those based on noise-tone differences. In general, the accuracy of the prediction methods decreased as the number of medications used by the subjects increased. It is argued that the results provide evidence for reticular activating system mediation of acoustic reflex activity.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

In a digitally controlled adaptive filter, ongoing detection and spectral analysis of quasi steady state noise are performed, and analog filter parameters are adjusted to provide greatest attenuation in frequency regions where noise energy is greatest. Attenuation introduced by the filter affects both speech and noise signals in the attenuation region. Effects of a master hearing aid incorporating an adaptive filter chip were assessed by measuring aided speech recognition threshold in noise with and without the filter. Performance of four hearing-impaired subjects showed that filter effects were related both to the frequency spectrum of the noise and to the distribution of speech information by frequency. No improvement in speech recognition threshold was seen for broadband speech materials in broadband noise. Better performance was observed for low-frequency noise in combination with speech materials for which the important information was confined to high frequencies.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Four hearing aid prescription methods were compared. A digital master hearing aid was used to produce the prescribed frequency gain characteristics. Measures of speech recognition and paired comparison judgments of relative speech intelligibility and speech quality were obtained at three output levels for each of the experimental frequency gain characteristics. No single prescriptive method emerged as being clearly superior. Relative performance of the four prescriptive methods varied as a function of output level. Similar results were observed for both speech recognition testing and paired comparison testing.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Forty-six hearing-impaired young adults were tested with a newly developed instrument that requires a discrimination response to assess viseme perception as a component of lipreading performance. Stimuli were videotaped sentences that differed on half of the trials from a captioned target sentence by one viseme embedded in the middle of the sentence. Discrimination within six visual categories was tested: gross syllable pattern, consonant articulation—lips, consonant articulation—tongue, vowel articulation—extreme lip shapes, vowel articulation—graded lip shapes, and vowel articulation—jaw movement. Test data were analyzed using an item response theory model. The results indicated that the test data conformed to the expectations of the Rasch model for person measurement. Relationships among subjects' test scores and communication characteristics also were examined. The data provide evidence that the test protocol, at this earty stage of development, is useful for assessing at least one perceptual component of lipreading performance.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Spectral analysis along with zero and standard-phase shift digital fittering were performed on evoked potentials recorded from 12 normal hearing subjects. The results indicated a progressive shifting of the mean spectral content of the ABR toward the low frequencies as the stimulus intensity was lowered. Despite this, the effects of zero-phase shift high-pass digital filtering at 100 Hz (36 dB/oct) did not significantly differ between waveforms elicited by a 75 dB nHL, 55 dB nHL, and 35 dB nHL stimulus. The major response frequency of the ABR is related to the distance between the peak (IV/V) and the following major trough (approximates one-half the response period). In waveforms where the major trough occurred before 10 msec, the use of 100 Hz, 36 dB/oct, zero-phase shift high-pass filters produced only a small reduction in response amplitude, even at low stimulus intensity levels. Waveforms which had a major trough (Na,) between 10 to 15 msec were reduced in amplitude by 100 Hz, 36 dB/oct, zero-phase shift high-pass filters (the longer period of the response energy in these waveforms corresponds to a lower energy frequency). However, this trough has a latency that prevents it from being recorded on a 10 msec time base or defined as an ABR. Based on these results, the use of zero-phase shift high-pass filters with a high-pass cutoff frequency that is equal to or less than the resolution of the time base (1/time base) appears to be a desirable method of reducing muscle artifact and other electrical contamination of the ABR. Used in this manner, the filter mainly served to eliminate baseline shift and to flatten a sloping baseline. Standard phase shift filters distorted the response and resulted in significant amplitude reduction at all stimulus settings.

ISSN:0196-0202    

出版商:OVID    

年代:1988

数据来源: OVID