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Biomedical subjects

W A Dreschler

Publications and source records attributed to W A Dreschler.

16 recordsLinked to original sources
PubMed1992

Late effects of radiotherapy on hearing.

The effect of radiotherapy on hearing was studied in 30 patients who were treated by surgery and radiotherapy for a parotid neoplasm. Functions of the irradiated ear were compared with those of the non-irradiated ear in the same patient. Tympanometry showed a small but significant reduction of static compliance on the irradiated side when compared with the non-irradiated side. Audiometry showed a significant increase in hearing loss in the 1-2, 4-8 and 10-20 kHz ranges that increased with frequency. This hearing loss was mainly sensorineural in contrast to hearing loss at 250-500 Hz, where it was more of a conductive type. There appeared to be a significant dose-effect relation in sound perception at 4-8 kHz. Doses to the cochlea of less than 55 Gy seldom caused a hearing loss, in contrast to doses exceeding 65 Gy. Overall, radiotherapy was found to cause significant, mainly sensorineural hearing losses, which were partly dose-dependent.

Acoustic Impedance Tests↗
PubMed1992

The effects of input-output configuration in syllabic compression on speech perception.

Speech perception was tested through a broad-band syllabic compressor with four different static input-output configurations. All other parameters of the compressor were held constant. The compressor was implemented digitally and incorporated a delay to reduce overshoot. We studied four different input-output configurations, including a linear reference condition. Normal-hearing and hearing-impaired subjects participated in the experiments testing perception of meaningful sentences as well as nonsense CVCs in carrier phrases. The speech materials were presented in quiet and in noise. The results from the CVCs were analyzed quantitatively in terms of scores and qualitatively in terms of phoneme confusions. Differences in speech perception due to the different input-output configurations were small. The input-output configuration with the highest amplification of low amplitude sounds yielded the best results. Detailed analysis of the results included a correlational analysis with a number of auditory functions characterizing the ears tested. The pure-tone audiogram provided parameters of auditory sensitivity: average audiometric loss and audiometric slope. Psychophysical tests provided parameters of temporal resolution and frequency selectivity: the temporal resolution factor, temporal gap detection, and auditory filter shape. The correlational analysis showed that the subjects with better temporal acuity obtained better results.

Adolescent↗
PubMed1992

Fitting multichannel-compression hearing aids.

Multichannel hearing aids have been introduced recently in clinical practice. In this paper, some advantages and disadvantages of multichannel hearing aids are discussed. The advantages include an improved use of compression. However, the number of settings will be larger in multichannel hearing aids and exact knowledge of the goal to be pursued by compression is more necessary than ever. Inexactness of the definitions of these goals may have been a reason for the contradictory results in the studies on multichannel compression. A number of requirements must be fulfilled for a successful application of multichannel compression. One of these is detailed knowledge about the perception of suprathreshold signals. For that reason, an extension of the battery of tests commonly used in rehabilitative audiology is necessary. Another requirement is that the fitting strategy is determined by the purpose of applying compression. The objectives will be different for compression limiting and syllabic compression. A fitting procedure used in clinical practice has to take into account some limitations in the fitting time available. A number of possible fitting tools are discussed. Two strongly different fitting strategies for the same commercially available three-channel compression aid illustrate fundamental differences in fitting philosophy.

Audiometry, Pure-Tone↗
PubMed1992

[Predictive value of high frequency audiometry in otosclerosis].

A study was carried out to evaluate the value of high-frequency audiometry in stapes surgery in cases of otosclerosis. The hearing function was measured pre- and postoperatively by means of conventional and high-frequency audiometry (Demlar 20k). The operative findings of the gradation of otosclerosis were compared with the pre and postoperative audiometrical measurements. The results of this study point out that a clear relation exists between the preoperative high tone audiogram and the gradation of otosclerosis. In conclusion, we state that high-frequency audiometry can predict the state of stapes fixation in otosclerosis and that can be important in stapes surgery.

Audiometry↗
PubMed1991

Advantages of directional hearing aid microphones related to room acoustics.

In this study, two types of hearing aids were used. Both aids had the same frequency characteristics for frontal sound, but one employed an omnidirectional microphone and the other a directional microphone. The frequency characteristics of both hearing aids were measured for five azimuths on KEMAR and in situ in 12 normal-hearing subjects. For these subjects we also determined the speech reception threshold (SRT) with background noise in two rooms with different reverberation times. The direction of the speech stimuli was always frontal; the direction of the noise was varied. Additionally, directional hearing was measured with short noise bursts from eight loudspeakers surrounding the subject. In the less reverberant room, sounds coming from behind were less amplified by the hearing aid with the directional microphone than by the one with the omnidirectional microphone. In this room the monaural SRT values were largely determined by the level of the background noise. For the directional hearing aids there was an extra binaural advantage which depended on the direction of the background noise. Only for low-frequency noise bursts was directional hearing better with directional hearing aids. In the more reverberant room, no distinct differences between the frequency characteristics of the two hearing aid types were measured. However, a systematic difference between monaural SRT values measured through the two hearing aids was found. This difference was independent of noise azimuth. In conclusion, hearing aid(s) with a directional microphone showed no disadvantages and clear advantages under specific conditions.

Acoustics↗
PubMed1990

Speech reception in reverberation related to temporal resolution.

In this study, the influence of temporal properties of the auditory system on speech recognition, either in noise or in both noise and reverberation, has been investigated. Temporal resolution parameters consisted of both the temporal resolution factor (TRF) and the minimum detectable gap (MDG). TRFs were measured for probe-tone frequencies of 500, 1000, and 3000 Hz; MDGs were measured for octave-band noises centered at 500, 1000, and 3000 Hz and for a wideband noise. TRF and MDG proved to be rather independent parameters of temporal resolution. For both temporal-resolution parameters, there was considerable overlap between the performance of the normal-hearing and hearing-impaired listeners. A correlation analysis shows that MDG for wideband noise is related to speech recognition in reverberation. However, there is a mutual dependence of speech recognition and MDG on the pure-tone audiogram.

Adolescent↗
PubMed1990

Pre- and postoperative high-frequency audiometry in otosclerosis. A study of 53 cases.

A study was carried out to evaluate the results of stapes surgery in 53 cases of otosclerosis. The hearing function was measured pre- and postoperatively by means of conventional and high-frequency audiometry (Demlar 20K). The operative findings of the gradation of otosclerosis were compared with the pre- and postoperative audiometrical measurements. The results of this study point out that a clear relation exists between the preoperative high-tone audiogram and the gradation of otosclerosis. Stapedotomy does not influence the high-frequency threshold postoperatively. In conclusion, high-frequency audiometry can predict the state of stapes fixation in otosclerosis and this can be important in stapes surgery.

Audiometry↗
PubMed1990

The temporal resolution factor with and without background noise.

In this paper we discuss the measurement of the temporal resolution factor (TRF). The major merits of this measurement are that it is simple enough to be used clinically and that the results are, within certain limits, independent of presentation level. Addition of a continuous background noise has been suggested to enhance the discriminative power of TRF between normal-hearing listeners and listeners with poor temporal resolution. However, we showed through a simple model that this background noise may introduce a strong dependence on presentation level, which must be taken into consideration. To test our model we developed a new measurement protocol. This protocol was applied in measurements of 5 normal-hearing and 9 sensorineurally hearing-impaired listeners. Their results could reasonably well be fitted by the model. The model predicts large measurement errors for TRF values determined with background noise. We found the standard deviations of TRF values, calculated from test and retest measurements, to be smaller in conditions without a continuous background noise. In addition, our results did not show the predicted enhancement in discriminative power between normal-hearing and hearing-impaired listeners. Therefore, the primary conclusion is that the determination of the TRF is not improved by adding a background noise.

Adaptation, Physiological↗
PubMed1989

Phoneme perception via hearing aids with and without compression and the role of temporal resolution.

Hearing impairment is more than a sensitivity loss. The causes of reduced discrimination can be found also in deteriorations in loudness perception (recruitment), frequency resolution and temporal resolution. Only recruitment can be compensated for by modern hearing aids, namely by the reduction of the dynamic range by means of compression. However, the introduction of compression introduces temporal distortions, which may deteriorate the temporal cues of speech. In this study the perception of nonsense consonant-vowel-consonant-words presented through hearing aids was studied in a group of 12 hearing-impaired listeners. Phoneme perception in conditions with and without compression was analyzed and related to temporal parameters of the listeners' hearing. A detailed analysis of the patterns of confusions revealed clear qualitative differences in the perception of phonemes with and without compression. These differences can be related to an improved perception of temporal cues like the preburst silent interval of plosives and to spectral changes induced by the activation of the compression circuit. A reduced temporal resolution is disadvantageous for the perception of temporal cues like plosive detection, but our data do not suggest that the perception of temporal cues is hampered excessively by temporal distortions from the compression circuit itself.

Adolescent↗
PubMed1989

Role of high-frequency audiometry in the early detection of ototoxicity. II. Clinical Aspects.

As a supplement to a previous paper [Dreschler et al.: Audiology 1985; 24:387-395] high-frequency (HF) audiometry was applied to compare the ototoxic effects of two different drug administration protocols for cis-platinum (CDDP). In both subgroups, HF audiometry considerably enhanced the early detection of ototoxicity. Marked differences between treatments have been established both in the pattern of onset of the damage and in the relation between dose and damage severity. For subjects treated with platinum derivatives, the thresholds at 12 and 14 kHz prove to be especially important. The results suggest that for these subjects the measurement of only a single frequency may be considered: with a minimum of effort, most of the increased sensitivity for a complete HF audiogram can be obtained. Finally, the relation between threshold deteriorations above 8 kHz and threshold deteriorations in the conventional range of audiometric frequencies has been investigated.

Adult↗
PubMed1988

The effect of specific compression settings on phoneme identification in hearing-impaired subjects.

In this study, some aspects of single-channel compression have been investigated in 15 hearing-impaired subjects and 4 normal-hearing listeners. Phoneme perception as a function of the compression-threshold level was measured for two hearing aids with input-dependent compression, differing in compression ratio and compression recovery time. Phoneme-identification scores, obtained by different hearing aids under similar conditions, did not differ significantly. However, there was a small but significant increase in identification scores for the lowest setting of the compression threshold. Some qualitative differences in the patterns of confusion could also be established. There are indications that compression reduces the relative contribution of frication and enhances the contribution of the second formant of vowels in phoneme perception.

Adolescent↗
PubMed1988

Dynamic-range reduction by peak clipping or compression and its effects on phoneme perception in hearing-impaired listeners.

In this study, differences between dynamic-range reduction by peak clipping and single-channel compression for phoneme perception through conventional hearing aids have been investigated. The results from 16 hearing-impaired listeners show that compression limiting yields significantly better phoneme identification scores than does peak clipping if a strong reduction of the dynamic range has to be effected. In addition, some qualitative differences in confusion patterns could be established: the perception of low-frequency information appears to be relatively important in compression limiting; the perception of plosiveness is less important.

Adolescent↗
PubMed1987

Auditory psychophysics: spectrotemporal representation of signals.

The study of audition has widened: Having been concentrated in the 1960s on a few topics like pitch perception, binaural hearing, and fatigue, it now spans many more subjects. In the present paper we have emphasized the following topics: frequency analysis--this topic includes spectral integration and resolution, auditory excitation patterns, and processing of spectral information; temporal analysis--this topic refers mainly to studies in which abstract and stylized temporal variations in stimuli are used; binaural hearing--a subfield that still attracts a great deal of attention because of its unique character; pitch perception--of particular interest is this field for the perception of prosodic features of speech, but it also addresses fundamental questions of how the auditory system works; and pathology of hearing--in particular the effects of impaired hearing on speech perception and the relations among various hearing-test results. (This section was written in collaboration with W. A. Dreschler.) Many of the topics discussed have a direct relation to the capabilities of the auditory system in analyzing sounds--in particular, speech sounds. Experimentally, the problem can be approached from two sides: in one the stimuli are generated in a stylized form, and in the other they are taken as distorted versions of actual speech elements. In this paper we have described mainly the first category of experiments. Whereas we know for certain that the auditory system operates in the frequency-temporal domain, it is remarkable that the distinction between fields 1 and 2 (above) can still be made. Temporal effects in frequency analysis are often considered as perturbations, and the same is true for spectral effects in the study of temporal resolution. A true integration of time and frequency is often sought but seldom achieved as the focus of study. Of the many subjects that would ideally have received more coverage we mention two: the use of additional stimulation pathways to help patients with large hearing loss or deaf-blind people, and the use of a cochlear prosthesis ("cochlear implant"). Because we lacked space to cover these topics adequately, we omitted them completely. This indicates no undervaluation of these subjects of study or of the benefits they can provide to hearing-impaired people.

Auditory Perception↗
PubMed1987

Speech understanding and directional hearing for hearing-impaired subjects with in-the-ear and behind-the-ear hearing aids.

With respect to acoustical properties, in-the-ear (ITE) aids should give better understanding and directional hearing than behind-the-ear (BTE) aids. Also hearing-impaired subjects often prefer ITEs. A study was performed to assess objectively the improvement in speech understanding and directional hearing afforded by ITE aids versus BTEs. In 28 hearing-impaired subjects, who visited our Centre for a check-up of their ITEs, the following parameters were measured: (a) thresholds for third-octave bandpass noises between 0.25 and 4 kHz, (b) speech reception thresholds for short Dutch sentences in quiet and with background noise, (c) directional hearing. All three experiments were done binaurally with the subjects wearing their ITEs, BTEs, and no hearing aid. With the 2-cc coupler, the gain used by the subject was measured. The SRT values for the ITE were significantly lower than those for BTE. More gain at 2 and 4 kHz in the ITE proved to be a responsible factor for this improvement. Directional hearing was not improved by wearing an ITE. Large interindividual differences were found between functional gain and the 2-cc coupler measurements. The mean functional gain at 4 kHz for an ITE is higher than the gain measured in a 2-cc coupler. For a BTE, the functional gain at 2 and 4 kHz is lower than the 2-cc coupler gain.

Adult↗
PubMedDate not supplied

High frequency audiometry in prospective clinical research of ototoxicity due to platinum derivatives.

The results of clinical use of routine high frequency audiometry in monitoring the ototoxic side effects of platinum and its derivatives are described in this prospective study. After demonstrating the reproducibility of the technique, we discuss the first results of an analysis of ototoxic side effects in 75 patients (150 ears). Significant differences in the pattern of hearing loss were registered for the different platinum treatment groups (cisplatin 20 mg/m2, cisplatin 50 mg/m2, and carboplatin 350 mg/m2). In the groups receiving cisplatin 50 mg/m2 and carboplatin 350 mg/m2, 42% and 25%, respectively, of the investigated ears proved to be undamaged, versus 9% undamaged in the group receiving cisplatin 20 mg/m2 (p less than .01). Ototoxic hearing loss started mainly (46% to 70%) in the higher frequencies (10,000 to 18,000 Hz) and developed into a broader-range hearing loss (1,000 to 18,000 Hz) during treatment in 13% to 43% (p less than .01). The onset of hearing damage was influenced by the patient's age (p less than .001) and the existence of a troubled otologic history (p less than .05). The study demonstrates the important role of high frequency audiometry in early detection and monitoring of ototoxic damage.

Adolescent↗