Biomedical subjects

R Katsch

Publications and source records attributed to R Katsch.

5 recordsLinked to original sources

PubMed2001

Maximizing effective audibility in hearing aid fitting.

OBJECTIVE: This paper examines why more audibility is not always better than less audibility if hearing-impaired people are to best understand speech. DESIGN: We used speech perception data from 14 normally hearing and 40 hearing-impaired people to quantify the contribution of audibility to speech intelligibility. The quantification revealed that the effectiveness of audibility decreased with hearing loss, and the decrement was greater at high frequencies than at lower frequencies. To apply the Speech Intelligibility Index (SII) model to predict speech intelligibility for hearing-impaired people, we modified the model to take account of effective audibility rather than physical audibility. RESULTS: The modified SII model provided an adequate description of speech performance of people with a wide range of hearing threshold levels. We applied the model to the evaluation of two prescriptions for a sloping audiogram at prescribed levels and at equated loudness levels to demonstrate the necessity of considering loudness and effective audibility in prescribing amplification. Effective audibility is defined as audibility corrected for the effects of level distortion and hearing loss desensitization, and this paper proposes a method of estimating effective audibility from hearing threshold level at different frequencies. CONCLUSIONS: The practical implication of considering effective audibility in prescribing hearing aids is that for a given listening level, less gain is provided at frequencies where the hearing is most impaired to allow more gain at frequencies where audibility is most useful. In developing the NAL-NL1 prescription for nonlinear hearing aids, we adopted the modified SII model together with a loudness model to derive optimal gain-frequency response characteristics that maximize predicted speech intelligibility for people with different degrees of hearing losses.

Audiometry, Speech↗

PubMed2001

NAL-NL1 procedure for fitting nonlinear hearing aids: characteristics and comparisons with other procedures.

A new procedure for fitting nonlinear hearing aids (National Acoustic Laboratories' nonlinear fitting procedure, version 1 [NAL-NL1]) is described. The rationale is to maximize speech intelligibility while constraining loudness to be normal or less. Speech intelligibility is predicted by the Speech Intelligibility Index (SII), which has been modified to account for the reduction in performance associated with increasing degrees of hearing loss, especially at high frequencies. Prescriptions are compared for the NAL-NL1, desired sensation level [input/output], FIG6, and a threshold version of the Independent Hearing Aid Fitting Forum procedures. For an average speech input level, the NAL-NL1 prescriptions are very similar to those of the well-established NAL-Revised, Profound procedure. Compared with the other procedures, NAL-NL1 prescribes less low-frequency gain for flat and upward sloping audiograms. It prescribes less high-frequency gain for steeply sloping high-frequency hearing losses. NAL-NL1 tends to prescribe less compression than the other procedures. All procedures differ considerably from one another for some audiograms.

Acoustic Stimulation↗

PubMed2000

Relative loudness perception of low and high frequency sounds in the open and occluded ear.

A comparison of published equal loudness contours indicates that different shapes are obtained at a comfortable level when the measurements are done in an occluded ear than when they are done in an open ear, even though all measurements are expressed as dB SPL at the eardrum. This paper presents the result from a loudness balancing test which confirms this observation. Eleven normal-hearing listeners balanced the level of a 500- and a 3000-Hz octave band babble-noise to the level of a 1500-Hz octave band babble-noise. The balancing test was completed in open and occluded ears using a loudspeaker and a hearing aid receiver, respectively. A probe tube microphone was used to measure the actual levels presented near the individual's eardrum. The results show that an average of 10 dB higher level was selected for the 500-Hz octave band when listening with the occluded ear than when listening with the open ear. A large range of factors is discussed, but no physical explanation for the discrepancy was found. The findings could have consequences for psychoacoustic experiments and for the use of loudness measurements for hearing aid prescription.

Auditory Threshold↗

PubMed1983

Dichotic listening in good and poor readers.

Dichotic listening performance using CV pairs was investigated in a group of 30 children, 15 good readers and 15 poor readers, aged 10-13 years. The results indicate that the poor readers did not demonstrate atypical laterality or phonetic processing effects, although there was a significant difference in their ability to identify both items on dichotic trials correctly. However, when the same stimuli were presented monotically, there was no difference in the performance of the groups. Additional testing indicated that the poor performance for the double-correct response class was also demonstrated in conditions where the dichotic stimuli were separated by as much as 500 and 1000 msec. These results support previous findings that reading-disabled children exhibit a deficit in their capacity to process two items on dichotic tasks. The implications of these results are discussed in terms of both neurological and auditory processing interpretations, and it is suggested that dichotic tasks are useful for investigating auditory processing problems in reading-disabled children.

Child↗

PubMedDate not supplied

Auditory processing limitations in low verbal children: evidence from a two-response dichotic listening task.

Evidence for auditory processing limitations based on the use of two-response consonant-vowel (CV) dichotic listening tasks is reviewed. These studies show that low verbal children obtain fewer trials on which both items are correctly identified (double correct responses). A study is reported comparing a group of good and poor readers on the dichotic CV task. These data are then analyzed in terms of a normative model which attempts to show the effects of overall performance and guessing on double correct responses. It is concluded, in terms of the model, that the poor double correct performance of the poor readers is the direct result of poor auditory processing capacity.

Auditory Perception↗