ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectiveThe aim was to measure the loudness of monaural and binaural stimuli in a group of cochlear implant users who had residual hearing in the nonimplanted ear, and to consider the implications of these measures for a binaural fitting consisting of a hearing aid and an implant in opposite ears. Three independent hypotheses were addressed: that the shapes of the electric and acoustic loudness growth functions would be similar, although the dynamic ranges would differ; that standard implant and hearing aid fittings would result in substantial loudness mismatches between the acoustic and electric signals; and that loudness summation would occur for binaural combinations of electric and acoustic signals.DesignA modified version of the “Loudness Growth in 1/2-Octave Bands” method (Allen, Hall, & Jeng, 1990) was used to measure loudness growth for each ear of nine subjects. At the time of the experiment, the subject group included all implant users in Melbourne and Denver who were available for research and who also had sufficient residual hearing to use a hearing aid in the nonimplanted ear. Five acoustic frequencies and five electrodes were measured for each subject. The same subjects also estimated the loudness of a set of stimuli including monaural and binaural signals chosen to cover the loudness range from very soft to loud.ResultsThe shapes of the averaged loudness growth functions were similar in impaired and electrically stimulated ears, although the shapes of iso-loudness curves were quite different in the two ears, and dynamic ranges varied considerably. Calculations based on the psychophysical data demonstrated that standard fitting procedures for cochlear implants and hearing aids lead to a complex pattern of loudness differences between the ears. A substantial amount of loudness summation was observed for the binaural stimuli, with most summation occurring when the acoustic and electric components were of equal loudness. This is consistent with observations for subjects with normal hearing and subjects with bilaterally impaired hearing.ConclusionsThese experiments provide data on which criteria and methods for the binaural fitting of cochlear implants and hearing aids may be based. It is unlikely that standard monaural fitting methods for cochlear implants and hearing aids will result in balanced loudness between the two ears across a reasonably broad range of frequencies and levels. It is also likely that output levels of both devices will need to be reduced relative to a monaural fitting to compensate for the binaural summation of loudness in some listeners.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectiveComparison of preverbal communication behavior in young children before receiving cochlear implants with outcomes 3 yr after implantation on speech identification and speech production tasks, to assess whether outcomes can be predicted from characteristics inherent to the child before implantation.DesignVideo recordings of preverbal communicative behavior were examined before use of the implant to quantify turn-taking and demonstration of autonomy by the child. Speech identification ability was measured 3 yr after implantation based on the Iowa Closed-Set Speech Perception Sentence Test, continuous discourse tracking, and an observational measure of telephone use. Speech production ability was measured 3 yr after implantation by the Edinburgh Articulation Test. Associations between the preimplant measures and the 3-yr outcomes were assessed by correlation analysis of data from 33 children.ResultsThe 3-yr performance measures of speech identification were correlated with the preimplant measure of autonomy. Telephone use and speech production ability were not significantly associated with the preimplant measures.ConclusionsUp to a fourth of the variance in speech identification performance 3 yr after cochlear implantation of young children may be predicted from characteristics that are inherent to the child before implantation. Those characteristics are represented by the demonstration of autonomy in preverbal communicative interactions, whether by means of vocalization or by gesture. If those characteristics are acquired during infancy, outcomes in children with auditory prostheses including cochlear implants may be enhanced by activities that encourage autonomy in early years.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectiveTo determine the effect of reduced dynamic range on speech understanding when the speech signals are processed in a manner similar to a 6-channel cochlear implant speech processor.DesignSignals were processed in a manner similar to a 6-channel cochlear implant processor and output as a sum of sine waves with frequencies equal to the center frequencies of the analysis filters. The amplitudes of the sine waves were compressed in a systematic fashion to simulate the effect of reduced dynamic range. The compressed signals were presented to 10 normal-hearing listeners for identification.ResultsThere was a significant effect of compression for all test materials. The effect of the compression on speech understanding was different for the three test materials (vowels, consonants, and sentences). Vowel recognition was affected the most by the compression, and consonant recognition was affected the least by the compression. Feature analysis indicated that the reception of place information was affected the most. Sentence recognition was moderately affected by the compression.ConclusionsDynamic range should affect the speech perception abilities of cochlear implant users. Our results suggest that a relatively wide dynamic range is needed for a high level of vowel recognition and a relatively small dynamic range is sufficient to maintain consonant recognition. We infer from this outcome that, if other factors were held equal, an implant patient with a small dynamic range could achieve moderately high scores on tests of consonant recognition but poor performance on vowel recognition, and that it is more likely for an implant patient with a large dynamic range to obtain high scores on vowel recognition than for an implant patient with a small dynamic range.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectivesThe goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growth.DesignTen adolescents and young adults with moderate to severe sensorineural hearing loss were fitted monaurally with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Threshold, upper limit of comfort and loudness growth were measured in the unaided, linear gain and WDRC conditions for warble tones, environmental sounds and speech. Twelve adult listeners with normal hearing also were tested monaurally in the unaided condition to provide normative data for comparison purposes.ResultsThe WDRC hearing aid provided a greater input dynamic range than the linear circuit for all stimuli. The dynamic range was normalized for more subjects with the WDRC than the linear hearing aid. In addition, exponential loudness growth functions fitted to the loudness growth data showed that, on average, loudness growth was more normalized with the WDRC hearing aid fitted to DSL[i/o] targets than the linear hearing aid fitted to DSL[i/o] targets.ConclusionsWDRC processing, fitted using the DSL[i/o] method, has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides an audible, comfortable and tolerable amplified signal across a wider range of inputs than linear gain processing, without the need for volume control adjustments.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectiveTo evaluate the impact of venting, microphone port orientation, and compression on the electroacoustically measured directivity of directional and omnidirectional behind-the-ear hearing aids. In addition, the average directivity provided across three brands of directional and omnidirectional behind-the-ear hearing aids was compared with that provided by the open ear.DesignThree groups of hearing aids (four instruments in each group) representing three commercial models (a total of 12) were selected for electroacoustic evaluation of directivity. Polar directivity patterns were measured and directivity index was calculated across four different venting configurations, and for five different microphone port angles. All measurements were made for instruments in directional and omnidirectional modes. Single source traditional, and two-source modified front-to-back ratios were also measured with the hearing aids in linear and compression modes.ResultsThe directivity provided by the open (Knowles Electronics Manikin for Acoustic Research) ear was superior to that of the omnidirectional hearing aids in this study. Although the directivity measured for directional hearing aids was significantly better than that of omnidirectional models, significant variability was measured both within and across the tested models both on average and at specific test frequencies. Both venting and microphone port orientation affected the measured directivity. Although compression reduced the magnitude of traditionally measured front-to-back ratios, no difference from linear amplification was noted using a modified methodology.ConclusionsThe variation in the measured directivity both within and across the directional microphone hearing aid brands suggests that manufacturer’s specification of directivity may not provide an accurate index of the actual performance of all individual instruments. The significant impact of venting and microphone port orientation on directivity indicate that these variables must be addressed when fitting directional hearing aids on hearing-impaired listeners. Modified front-to-back ratio results suggest that compression does not affect the directivity of hearing aids, if it is assumed that the signal of interest from one azimuth, and the competing signal from a different azimuth, occur at the same time.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

ObjectiveThe purpose of the study was to evaluate the validity of predicting the real-ear aided response by adding customized acoustic transform functions to the performance of a hearing aid in a 2-cc coupler.DesignThe real-ear hearing aid response, the real-ear-to-coupler difference (RECD/HA2), and field to behind-the-ear microphone transfer functions were measured in both ears of 24 normally hearing subjects using probe-tube microphone equipment. The RECD/HA2 transform function was obtained using both insert earphones and with the hearing aid/pressure comparison method. An RECD/HA2 transfer function was also obtained with a customized earmold, ER-3A foam tip, and an oto-admittance tip.ResultsValidity estimates were calculated as the difference between the derived and measured real-ear response. The derived response was generally within 5 dB of the measured real-ear response when it incorporated an RECD/HA2 transform function obtained with a customized earmold for the specific ear in question. Discrepancies increased when the RECD/HA2 transfer function was obtained from the same subject but the opposite ear. There were significant differences between the RECD/HA2 transform function obtained with customized and temporary earmolds. As a result, the derived response incorporating these transforms differed significantly from the measured real-ear response obtained with the customized earmold. The insert earphone and the hearing aid RECD/HA2 transfer function were equally valid.ConclusionsThe derived response may be used as a substitute for in situ hearing aid response procedures when it incorporates acoustic transform functions obtained with a customized earmold from the specific ear in question.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Over the past few years, there has been increased interest in studying some of the cognitive factors that affect speech perception performance of cochlear implant patients. In this paper, I provide a brief theoretical overview of the fundamental assumptions of the information-processing approach to cognition and discuss the role of perception, learning, and memory in speech perception and spoken language processing. The information-processing framework provides researchers and clinicians with a new way to understand the time-course of perceptual and cognitive development and the relations between perception and production of spoken language. Directions for future research using this approach are discussed including the study of individual differences, predicting success with a cochlear implant from a set of cognitive measures of performance and developing new intervention strategies.

ISSN:0196-0202    

出版商:OVID    

年代:2000

数据来源: OVID