ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Evoked potentials are usually analyzed in the time domain (voltage versus time). The most familiar frequency-domain measure, the power spectral density function, displays power as a function of frequency but doesn't distinguish signal power from noise power. The coherence function estimates, for each frequency, the ratio of signal power to total (signal plus noise) power and, thus, indicates the degree to which system output (scalp potential) is determined by input (acoustic stimulus). Coherence ranges from 0 to 1; values above specified critical values can be accepted as demonstrating statistically significant system response. In this paper, we present coherence analysis of human scalp responses to clicks and amplitude-modulated tones. In both cases, this analytic method provides insight into the spectral character of the response (for example, assisting in specifying desirable filter characteristics). Threshold sensitivity is also improved: statistically significant responses can be detected at lower intensity by coherence analysis than by inspection of time-domain waveforms.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This study explored further the relationship between peripheral and central auditory maturation on the basis of the auditory brain stem response. Auditory brain stem responses were recorded in preterm infants and adults to rarefaction and condensation click stimuli transduced through insert Tubephones@. Infant recordings presented a triphasic waveform preceding wave I similar to that of the cochlear receptor potentials seen with adults during electrocochleography. Wave I latency and amplitude were found to be equivalent to those of adult subjects. Moreover, neither latency nor amplitude variability among infant wave I responses was found to be any greater than adults. Laencies of waves 111 and V, however, exhibited the expected differences relative to the adult comparison group. When the indirect evidence of cochlear receptor potentials in the infant are viewed adjacent to the observations that their ABR wave I latency, amplitude, and variability were entirely consistent with those of young adults, the data lend strong support for peripheral auditory electroma-turity. These data are discussed relative to previously published reports of prolonged wave I latency in the infant which was attributed either to middle ear effects or immaturity of the cochlea and first order Vlllth nerve neurons.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The cochlear nerve action potential (AP) was monitored during two types of hearing preservation surgery: (1) removal of small cerebellopontine angle tumors and (2) retrolabyrinthine vestibular nerve section. The purpose of this investigation was to study the relationship between changes in intraoperative AP latency, amplitude, and threshold, and changes in audiometric hearing subsequent to surgery. The presence or absence of a cochlear nerve AP toward the end of surgery accurately predicted the presence or absence of postoperative hearing (93%). Regression analyses were performed to explore the relationship between audiometric pre- and postoperative thresholds and intraoperative AP threshold changes. Statistically significant relationships were found for (1) pre-operative audiometric thresholds and initial AP click thresholds (p = 0.0068); (2) final AP click thresholds and postoperative audiometric thresholds (p = 0.0003); (3) AP click (p = 0.0001) and 1 kHz (p = 0.0006) threshold shifts and pre-to postoperative audiometric threshold shifts. No relatiohship was found between either AP latency or amplitude values and postoperative hearing. Intraoperative threshold measurements can be used as an indicator of hearing change. If amplitude or latency indices are also monitored it may be better to use stimulus levels close to the evoked potential threshold.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The Connected Speech Test (CST) is used to measure the intelligibility of everyday speech; it is intended primarily for quantifying hearing aid benefit. The test consists of 48 passages of conversationally produced connected speech, each passage concerning a familiar topic and comprising 10 sentences. Listeners are apprised of the passage topic in advance and are required to repeat the sentences one at a time. Each passage contains 25 scoring words. The test is recorded audiovisually. In previous papers, we have reported the development of the test materials and investigations of the use of the audio portion with normally hearing and hearing-impaired listeners. Audio versions of the test have been developed for use with normal hearers (CST version l), and for hearing-impaired listeners (CST version 2). In the present paper, we report a study of the test administered audiovisually. Twenty-six normally hearing subjects responded to audiovisual presentation of all 48 test passages. On the basis of the results, a new version of the test (CST version 3) was generated. In this new version, the test passages are presented in designated sets of four or six passages. The critical difference between two scores is estimated to be the same for both audio and audiovisual administration.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Monosyllabic rhyme words were dichotically presented to normal and complete split-brain subjects. In the normal adult population, only one of the words in the dichotic condition was identified. Hence, normal performance was about 50%, with a small but significant right-ear advantage. The split-brain patients yielded the expected marked left deficit, as seen on other dichotic speech tests, and demonstrated a right-ear enhancement, producing a large interear difference. This right-ear enhancement on the dichotic rhyme task (DRT) may suggest a release from central auditory competition in the left hemisphere. The dichotic rhyme task's normative data results and sensitivity to lack of callosal transmission make it worthy of further clinical and basic research.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In this report we describe the vowel identification ability of eight patients who scored above 70% correct on a test of spondee word identification. The stimuli were 12 synthetic vowels in “bVt” format. The vowels differed in the frequency of F1, F2, and F3. The mean identification accuracy was 60% correct. Front vowels and dipthongs, /3/, and /u/ were relatively well identified. The vowels in “but,” “bought,” and “bout,” which were characterized by high F1 s and low F2s were not well identified. The results are consistent with a model of recognition in which FI is specified, with relatively good accuracy, by a rate code and in which extreme values of F2 are specified by a ratelplace code.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We describe the word recognition ability of 50 patients who use the multichannel cochlear implant manufactured by Symbion, Inc. The median scores for open set tests involving auditory stimulation alone were: 14% correct (range 0 to 60) for monosyllabic words, 44% correct (range 0 to 100) for spondees, and 45% correct (range 0 to 100) for words in the Everyday CID Sentences. In the visual stimulation condition of the Everyday CID Sentences, the median score was 64% correct (range 0 to 100). In the visual plus auditory stimulation condition, the median score was 99% correct (range 46 to 100). These results demonstrate that relatively good speech understanding can be achieved using a cochlear implant which employs only a few channels of stimulation and which simultaneously activates mon-opolar electrodes.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Hearing aids with signal processors use advanced circuitry to enhance speech recognition in noise. The effectiveness of these processors has not been well established. The purpose of this study was to evaluate performance on a speech recognition in noise task for listeners wearing a Zeta signal processor aid with the processor turned on and with the processor turned off. In addition, comparisons were made to performance while unaided and aided with a conventional hearing aid. A simple adaptive procedure and a psychometric function were the procedures used. Results for normal-hearing subjects indicate performance was usually better without a hearing aid. Performance when aided was similar for the processor on and the conventional aid. Performance in both of these conditions was clearly better than with the signal processor off. Although results for the hearing-impaired subjects varied widely, there was a trend for better performance with the conventional aid and with the signal processor on than for the signal processor off condition.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

In hearing aid research and application it is often necessary to transform the sound pressure level or acoustic gain measured at one physical point (e.g., 2 cc coupler) to an equivalent value at another physical point (e.g., tympanic membrane). Results of currently available studies on various transformations are summarized in this report. When no data were available, the desired transfer function was calculated as a linear combination of known contributing transfer functions. Values are given for the center frequencies of 1/3 octaves and critical bands.

ISSN:0196-0202    

出版商:OVID    

年代:1989

数据来源: OVID