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At least 343 records · Page 19Linked to original sources
PubMed1980

[Occupational hearing loss as probability diagnosis (author's transl)].

The paper discusses the question of which factors that are to be taken into consideration are of relevance to the expert in making his differential diagnosis in cases of occupational hearing loss. On the basis of the medical literature and earlier investigations the discussion is concerned with the proof of recruitment as well as with the effects of the exposure level and the exposure duration. Special reference is made to the "typical" hearing-threshold curve. The result of the examination with factor-analysis of 14,684 pure tone audiograms suggests that a small involvement of low and medium frequencies in the hearing loss is especially typical of occupational hearing losses. Not even this method permits delineating the effects of age on hearing from those of exposure to noise. The varying (pathogenetic) exposure level has a strikingly low influence on the extent of the occupational hearing loss. The entire data resulting from 25.544 pure tone audiograms are furthermore used for the computation of hearing-loss curves of different tail probability (supposing a normal distribution). The expert has thus a means available to estimate the probability of whether or not a concrete case is still a typical example of occupational hearing loss.

Aging↗
PubMed1982

A model for the speech-reception threshold in noise without and with a hearing aid.

This paper presents a summary of the main results of our current research programme on the speech-reception threshold for sentences as a function of the sound-pressure level of interfering noise. The experimental results agree with a simple quantitative model in which every hearing loss for speech is interpreted as the sum of a class-A loss (attenuation), characterized by a reduction in the levels of both speech signal and noise, and a class-D loss (distortion), comparable to a reduction in S/N ratio. The experiments confirm the model's prediction that a hearing aid can compensate for class-A hearing losses but, generally, not for class-D hearing losses. The implies that the problem of having difficulties in understanding speech in a noisy environment, which is the primary handicap of hearing-impaired subjects, is not solved by the hearing aid.

Audiometry, Speech↗
PubMed1982

Loudness recruitment in abrupt drop sensorineural hearing impairment.

Monaural bifrequency loudness balance tests were performed on 11 adults with abrupt drop sensorineural hearing impairment. To study frequencies on the slope, 2-octave Bekesy threshold measurements were made beginning at a frequency exhibiting normal hearing nearest to initiation of the slope (F1). Loudness was matched (Test 1) between F1 and F2 (a frequency nearest to termination of the slope), (Test 2) between F1 and F1 + F2/2 (a frequency halfway between F1 and F2), and (Test 3) between F1 and 2F1 (a frequency an octave above F1). Our data indicated that a combination of asymptotic and straight-line recruitment was demonstrated in Test 1, pure asymptotic recruitment in Test 2, and straight-line recruitment in Test 3. It was speculated that diffuse hair cell lesions such as in frequency areas in the vicinity of 2F1 in abrupt drop sensorineural hearing impairment or endolymphatic hydrops may show straight-line recruitment, and discrete outer hair cell lesions such as frequency regions around F1 + F2/2 may demonstrate pure asymptotic recruitment. Our results were discussed in relation to histopathological findings of human and animal subjects with abrupt drop hearing loss reported by other investigators. Data appeared to show a relationship between the types of loudness recruitment and the hair cell damage.

Adult↗
PubMed1980

[A contribution to binaural impulse modulaton (author's transl)].

The reported investigations shall detect possiblilties for using binaural impulse modulation with an interaural loudness difference to differentiate between normal and pathological hearing. The different curves between modulation and pure tone thresholds indicate cochlear lesions (recruitment) as well as such within the binaural pathways.

Audiometry, Pure-Tone↗
PubMedDate not supplied

[Occupational hearing loss and study of the recruitment by the brain stem auditory potentials].

We have studied 60 ears initial stage professional acoustic trauma and a hearing loss in the 2,000 and 4,000 frequencies at 30-40 db. We also included in the study 60 normal ears as the control group. In the first group we investigated the recruitment by the SISI test. Watson and Tolan's test, vocal audiometry and Metz's test. Recruitment was considered positive when indicated so by two of four tests. In waves I and V of BERA we have obtained the following results compared to those of the normal ears: Amplitude is similar in both waves, whatever the intensity of the click. Latencies increase with weak clicks, more in wave V, while the become equal with stronger clicks, what means the existence of recruitment. While other tests are not useful or doubtful, BERA are of interest for the study on recruitment in deep hearing loss.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1993

Multifocal amplification, a decisive step in recruitment compensation.

After several years of intense research the people at the Eriksholm Research Center in Denmark have found a new amplification principle that compensates for Loudness Recruitment in sensorineural hearing losses. This new amplification principle has been the basis for the development of the world's first fully automatic non-linear hearing aid: MultiFocus. The non-linear amplification has been found superior to the traditional linear amplification in every sense and improves life quality for the hearing impaired due to: increased listening range, improved speech intelligibility in noise, less or no problems with own voice, less occlusion problems, always correct loudness in different listening situations. One may conclude that from now on the hearing impaired can concentrate on what they hear rather than concentrate on hearing. Though simple, the fitting method for a non-linear hearing aid is different from that of a linear hearing aid. For the hearing aid fitters the challenge is to get familiar with this new way of fitting.

Amplifiers, Electronic↗
PubMed1994

[Loudness scaling. A procedure for quantitative recruitment detection].

Direct loudness scaling has been known as an audiological tool for about four decades. Although numerous publications have shown its clinical importance, loudness scaling has not been used in audiology and hearing aid fitting until now. This might be due to the lack of audiometers equipped with loudness scaling devices as well as missing evidence for its clinical applicability. In this study normal data for a single-step direct scaling procedure were established and loudness determinations of 105 patients with sensorineural hearing losses collected. The results show that normal level loudness functions exhibit very similar shapes for narrow band stimulation in the frequency range of 500 to 4000 Hz. However, loudness scaling is affected by the gender of the subjects: females scale systematically louder than do males. In hearing-impaired subjects the slopes of the level loudness functions tend to decrease with increasing hearing loss, indicating negative recruitment. This holds particularly true in the high-frequency range, e.g. at 4000 Hz. Our long-term experience with single-step direct loudness scaling has proven its clinical feasibility in typical patients of an audiology unit. Loudness scaling will prove useful for the localization of hearing impairments, as it can be employed as a quantitative indicator of recruitment without any restrictive preconditions. In addition, it allows the evaluation of hearing aids and cochlear implants by frequency-specific gain measurement.

Audiometry, Pure-Tone↗
PubMed1993

Effect on the speech reception threshold in noise of the recovery time of the compressor in the high-frequency channel of a two-channel aid.

This paper describes two experiments in a series evaluating and optimising a hearing aid incorporating two forms of automatic gain control (AGC). The first form is a front-end AGC which is normally slow acting and which compensates for variations in the overall level of speech from one situation to another. The second form of AGC follows the front-end AGC. The signal is split into two frequency bands, and fast-acting AGC is applied in the upper band only. The bands are then recombined. The two experiments described here were aimed at determining the optimum value of the recovery time of the AGC in the high-frequency channel. Speech reception thresholds (SRTs) were measured in the presence of speech-shaped noise as a function of the recovery time, for subjects with mild-to-moderate sensorineural loss. In the first experiment the recovery time was varied over the range 10-80 ms. SRTs tended to be lowest (best) at the shorter recovery times but the effects were small. In the second experiment, the recovery time was varied over the range 5-320 ms. In this case, there was a clear trend for SRTs to increase with increasing recovery time. A recovery time of about 20 ms appears to be optimal.

Aged↗
PubMed1993

[Diagnostic value of the peripheral and central vestibular recruitment and decruitment].

The subject of our investigation was the diagnostic value of the distinguish of peripheral and central type of the vestibular recruitment and decruitment. The examination was performed in the healthy subjects and in the two groups of the peripheral and central vestibular pathology cases. For the definition of the presence of peripheral or central type of the recruitment/decruitment phenomenon we used Ghosh and Kacker method for the labyrinth irritation. The results of this study show that for more detail topographic diagnosis of the vestibular disorders one must search the type of recruitment and decruitment.

Adult↗
PubMed1993

Real-time multiband dynamic compression and noise reduction for binaural hearing aids.

A multi-signal-processor set-up is introduced that is used for real-time implementation of digital hearing aid algorithms that operate on stereophonic (i.e., binaural) input signals and perform signal processing in the frequency domain. A multiband dynamic compression algorithm was implemented which operates in 24 critical band filter channels, allows for interaction between frequency bands and stereo channels, and is fitted to the hearing of the individual patient by a loudness scaling method. In addition, a binaural noise reduction algorithm was implemented that amplifies sound emanating from the front and suppresses lateral noise sources as well as reverberation. These algorithms were optimized with respect to their processing parameters and by minimizing the processing artifacts. Different versions of the algorithms were tested in six listeners with sensorineural hearing impairment using both subjective quality assessment methods and speech intelligibility measurements in different acoustical situations. For most subjects, linear frequency shaping was subjectively assessed to be negative, although it improved speech intelligibility in noise. Additional compression was assessed to be positive and did not deteriorate speech intelligibility as long as the processing parameters were fitted carefully. All noise reduction strategies employed here were subjectively assessed to be positive. Although the suppression of reverberation only slightly improved speech intelligibility, a combination of directional filtering and dereverberation provided a substantial improvement in speech intelligibility for most subjects and for a certain range of signal-to-noise ratios. The real-time implementation was very helpful in optimizing and testing the algorithms, and the overall results indicate that carefully designed and fitted binaural hearing aids might be very beneficial for a large number of patients.

Adult↗
PubMed1996

[Pathologic mechanoelectric transduction of outer hair cells as the cause of recruitment].

It is believed that the sound-induced travelling wave in the mammalian cochlea is enhanced and sharpened by a positive feedback mechanism. This causes the passive linear basilar membrane growth function to become non-linear. The present paper shows that nonlinear basilar membrane vibration is due to the nonlinear growth function of the receptor potential of outer hair cells, which can be described by a 2nd-order Boltzmann function. Since intensity coding in the inner ear depends on an interaction of nonlinear basilar membrane motion and nerve fibers with three different types of synaptic threshold and growth function, the process is directly dependent on an intact mechanoelectrical transduction of outer hair cells. According to the proposed model, a loss in efficiency of outer hair cell mechanoelectrical transduction must lead to both a reduction in gain (i.e., hearing loss) and a linearizing of the response. As a result, once above threshold, the changes of stereociliary displacement, basilar membrane displacement and neural firing rate per unit change of sound intensity must be larger than for the healthy cochlea with its compressive nonlinearity.

Animals↗
PubMed1996

Effect of hearing aid experience on preferred insertion gain selection.

The effect of hearing aid experience (measured as years of hearing aid use and user insertion gain at octave frequencies from 250 Hz to 4000 Hz) on the selection of preferred insertion gain under six listening conditions and one vocalization condition was examined. Thirteen experienced hearing aid users selected their preferred insertion gain in each test condition using a modified simplex procedure. The results showed that for the listening conditions, preferred insertion gain was highly correlated with the subjects' hearing loss from 500 Hz to 2000 Hz. Hearing aid experience did not correlate at all with preferred insertion gain. On the other hand, user insertion gain at 250 Hz and 500 Hz correlated highly with preferred insertion gain selected during vocalization. Years of hearing aid use did not correlate with preferred insertion gain selection. These results suggest that user insertion gain can affect preferred insertion gain selection only when the test conditions are identical to those that the hearing aid wearers experience in everyday lives. In typical laboratory conditions, preferred insertion gain is likely determined by the stimulus characteristics and subjective preference.

Adult↗