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PubMed1992

Prescriptive hearing aid fitting by parameter adjustment and selection.

We describe the rationale for the development of a psychophysical procedure that allows individual listeners to adjust the frequency-gain characteristic of a programmable hearing aid on a unidimensional scale, based on a target-gain reference value. The listener's task is to adjust the frequency response and select the parametric value judged to optimize the intelligibility or quality of speech. Originally described as the Sliding Scale, the procedure has been modified for use in reliability and validity studies of hearing aid fitting at Michigan State University. The modified approach is referred to as the Parameter Adjustment and Selection (PAS) procedure. Primary immediate goals for the procedure are ease of use, high reliability, and rapid clinical administration. The procedure, which may offer potential advantages over a paired-comparison approach, appears to be generally applicable to the fitting of digitally programmable hearing aids.

Auditory Threshold↗
PubMed1992

[Follow-up of sound pressure level at the tympanic membrane at varying impedance of the tympanic membrane-ossicular system].

We investigated the influence of varying compliance of the tympanic membrane on the sound pressure level of the human ear canal using a model with adjustable compliance. Decrease of compliance augments the sound pressure close to the tympanic membrane due to the increase of reflected sound pressure. This augmentation occurs in a narrow frequency area near the maximum resonance frequency and reaches 6 dB (SPL). These experimental data correlate well with clinical investigations in patients with middle ear effusion before and after operation and in patients performing the Valsalva manoeuvre.

Acoustic Impedance Tests↗
PubMed2006

[Difficulties encountered by old patients wearing a hearing aid].

Presbycusis is a common cause of deafness in the elderly. The histopathology shows degenerative changes of the hair cells in the organ of Corti, and of the auditory nerve fibers. This implies a loss of sensibility for low intensity stimuli, although the perception of loud sounds remains normal. The dynamic range of the cochlea is therefore reduced. In addition, the discrimination is also altered. Hearing aids do not restore a normal hearing. Manufacturers have reduced their size, making them difficult to handle by old patients. This paper reports some of the difficulties encountered by old patients suffering from presbycusis, their family members, doctors, and nurses are not always aware of.

Adult↗
PubMed2006

[Polish language dychotomic tests for speech audiometry Part 2: A study of people with normal hearing from various age groups].

INTRODUCTION: Evaluation of the objective results in the clinical examination of central auditory disorders requires the use of reliable language tests which provide the means for the estimation of patients' audio-verbal communicative skills. MATERIALS AND METHODS: The authors present a new set of more difficult language tests in Polish, including a filtered speech test, numeral and verbal dichotic tests and the normal Calearo test. The tests were evaluated on a group of people with good hearing from various age groups. CONCLUSIONS: The presented tests are the only existing ones created for the Polish language which expand the diagnostic possibilities in the case of central auditory processing disorders. It was found that there is a right ear predominance in dichotic tests, which grows together with the patient's age. This observation can be very beneficial in practice, allowing for hearing aids to be better fitted.

Adult↗
PubMed1991

[Clinical study of speech understanding in noise].

The goal of this study was to determine the extent to which the difficulty frequently experienced by hearing-impaired listeners in understanding noisy speech can be clinically described in terms of the auditory site of lesion. To this end, shifts of speech reception threshold in noise, using standardized franco-québécois bisyllabic word lists, were obtained from noise-exposed workers and compared to Plomp's model to ascertain content validity. Shifts resulted from monaural listening to a broad-band speech spectrum noise held constant at 0 dB signal-to-noise ratio. In this manner, increasing the presentation levels of both speech and noise was expected to progressively minimize the contribution of Plomp's class A attenuation component to speech hearing loss and eventually show an unequivocal manifestation of its distortion component (class D speech hearing loss). Listeners were 457 noise-exposed workers giving a total of 914 observations. Rejection of those ears with suspected middle-ear pathology led to a reduction to a total of 709 observations representing various degrees of permanent hearing impairment. An additional 98 observations showed normal hearing sensitivity in spite of noise exposure averaging 9.6 years. Results indicated the presence of five categories of speech threshold shifts varying independently of hearing sensitivity. 59.8% of those observations with permanent hearing impairment (424/709) simultaneously showed a problem understanding speech in noise. On 78 occasions, listening in noise was so disturbed that the 50% performance level corresponding to the speech threshold could no longer be established within reasonable limits, that is up to 65 dB above the speech threshold in a quiet environment. Conversely, 26.5% of the observations with essentially normal hearing sensitivity (26/98) showed reduced speech reception in noise. Fitting Plomp's model confirmed our expectations for two of the five categories of scores. A principal component analysis identified similar behaviour of speech threshold shifts in noise compared with Plomp's class D speech hearing loss. Hence, these speech threshold shifts in noise were interpreted as predominantly reflecting peripheral auditory disorders, that is defective frequency selectivity and temporal resolution. The remaining categories were found to be under the predominant influence of two other mechanisms: (1) band width reduction resulting from impaired hearing; (2) disorders associated with certain non-auditory cognitive factors, namely selective attention and the ability to make use of the redundancy of the message.

Adult↗
PubMed1991

Effect of UCL on aided Articulation Index calculation.

Nine hearing threshold patterns and uncomfortable loudness level combinations were used in comparing three hearing aid prescriptive procedures by means of a modified Articulation Index. In a minority of the comparisons a small dynamic range required a reduction from the gain that would have been prescribed. For these cases reducing the real-ear gain, in turn, resulted in a mean lowering of the Articulation Index by 0.03 for POGO and 0.08 for the Berger Method.

Amplifiers, Electronic↗
PubMed1991

[Relations and variability of the stapedial reflex threshold and psychoacoustic discomfort threshold].

Ten normal hearing subjects were subjected to repeated measurement of the stapedial reflex threshold (RT) and loudness discomfort threshold (DT) during five separate sessions. On the average DT was 4.8 dB higher than the RT. The sessions did not affect the intra-individual variance of either threshold. A regression analysis demonstrated that a significant linear relationship exists between RT and DT. However, DT may be lower than RT when the latter is shifted towards its upper variance boundary. Hence, RT and DT are not equivalent as indicators of the upper limit of loudness tolerance; since DT revealed a low intra-subject variance, such a psychoacoustic measurement may be reliably used for clinical purposes.

Acoustic Impedance Tests↗
PubMed1990

How much do we gain by gain control in hearing aids?

This paper considers three rationales for the use of automatic gain control (AGC) in hearing aids, and particularly multi-channel AGC. One rationale is to restore loudness relations among the acoustical elements of speech to what they would be for a normal ear. At present, there seems to be little evidence to support the idea that such loudness relations are critical for speech intelligibility. A second rationale is to reduce the effects of narrowband interfering sounds. This may be applicable in some restricted situations, but not in many others. The third rationale, the one considered here to be most important, is to ensure that all of the important elements in speech are comfortably audible. This can be achieved using two forms of AGC: slow-acting AGC operating on the whole speech signal, to compensate for variations in overall sound level from one situation to another; and fast-acting (syllabic) compression acting independently in a number of bands, to compensate for differences in level of acoustical elements within speech. To reduce spectral and temporal distortions introduced by the syllabic compression, the number of bands should be small (probably two or three) and the amount of compression should be the minimum required to ensure that all of the important elements in speech are audible. It is concluded that gain control can be useful for increasing user comfort and for ensuring the audibility of speech sounds. It is not likely to restore impaired hearing to normal for most patients, but may usefully be employed in conjunction with other forms of signal processing.

Equipment Design↗
PubMed1990

Spectral frequency and the modulation of the acoustic startle reflex by background noise.

The rat's (Long-Evans) acoustic startle reflex to a high-frequency tone burst (10.5 kHz) was depressed by intense high-frequency band-pass noise (8-16 kHz) but enhanced by low frequency noise (1-2 kHz). However, contrary to the hypothesis that the depression of startle in intense background noise is produced by sensory masking, the reflex to a low-frequency tone burst (at 1 kHz) was depressed by both high- and low-frequency band-pass noise. Two additional hypotheses are offered to supplement sensory masking in order to explain the asymmetry in these data. The first is that the intratympanic reflex, which acts as a high pass filter on acoustic input, is elicited in intense backgrounds. The second is that acoustic startle reflexes elicited by intense low-frequency tones are in part elicited by their high-frequency distortion products and that these distortion products are then masked by high-frequency background noise.

Animals↗
PubMedDate not supplied

[Loudness measurement and automatic control in the acoustic analyzer].

A block diagram of a hearing system is presented in which external hair cells are used to measure the loudness level and to adjust automatically internal hair cells. This system may assure an optimal function of the basic acoustic systems responsible for sound analysis. The data presented form a theoretical foundation for an adequate physiological interpretation of the recruitment phenomenon recorded in certain forms of neurosensory hypoacusis.

Hair Cells, Auditory↗
PubMed1987

[Processing of acoustic stimuli in the inner ear--a review of recent research results].

This review presents recent findings on the micromechanics of the basilar membrane. Active processes are essential for basilar membrane motion. It may be that contractile proteins within the outer hair cells play an important role for this amplification. The coding of acoustic information within the auditory nerve depends on spectral analysis (place information) as well as on the time structure of the stimulus. This latter time analysis seems to play a major role.

Auditory Threshold↗
PubMed1989

[A dynamic model of loudness adaptation].

Previous research on loudness adaptation has provided heterogeneous and partly contradictory results. One major reason seems to be the inconsistent use of the term 'adaptation', which is due to differing operational definitions. Here, a measurement-theoretic definition of loudness adaptation is introduced, which also comprises a new method for the identification of certain linear dynamic systems. This is of particular interest, since there is a lack of dynamic models describing loudness adaptation. An experiment with sinusoidal sound stimuli (3000 Hz) was performed to test whether loudness adaptation can be modeled by such a linear system. The results of the system identification indicate that this is possible. Therefore, it can be concluded that the given definition of loudness adaptation might be appropriate and that the method of system identification is an applicable research tool.

Adult↗
PubMed1989

Comfortable loudness level: stimulus effects, long-term reliability, and predictability.

This paper reports the results of a series of investigations of comfortable loudness levels with particular reference to their application to hearing aid gain prescriptions. Experiment 1 studied the effects of several stimulus waveforms, bandwidths, and durations on comfortable loudness levels for normal and hearing impaired listeners. Speech band comfort levels were found to be significantly higher than equal-duration noise band or warble tone comfort levels. Comfortable loudness levels were found to be independent of warble tone modulation parameters and of stimulus bandwidth (stimuli did not exceed critical bandwidths). In Experiment 2, reliability of comfortable loudness levels was evaluated in hearing-impaired subjects over two consecutive 1-year periods. Results indicated that comfortable loudness levels were slightly less reliable than thresholds. In addition, the results were consistent with a hypothesis that exposure to amplified sound produces a small increase in comfortable loudness levels. In Experiment 3, data from 67 hearing-impaired subjects were used to develop regression equations for prediction of comfortable loudness levels. Thresholds at the test frequencies were combined with comfortable loudness data at 500 Hz and 4,000 Hz. The prediction method was then evaluated using a new group of 25 subjects. Accuracy of predictions of comfort levels was substantially better with the new method than with an older method that relied exclusively on threshold data. Relevance of the outcomes to hearing aid fitting procedures is discussed.

Adult↗
PubMed1989

[Comparison of auditory threshold and loudness in the Bing test].

The threshold and loudness comparison techniques of the Bing test were performed in a quantitative manner in both ears of 14 subjects. The results were related to their air-bone gap at 500 Hz. The study showed that the air-bone gap influenced a positive occlusion effect, but did not influence its subsequent magnitude. The magnitudes of the results of the occlusion test performed in these two ways were significantly related to each other.

Adult↗
PubMed1979

Level dependence of critical bandwidth: notched-noise masking paradigm.

The effect of increased stimulus level on critical bandwidth was investigated. Noise-masked, pulsed-tone thresholds were obtained by a Bekesy tracking procedure from 4 practiced normal-hearing adults at .5, 1, 2, and 4 kc/s. Tones were placed symmetrically within a band-reject region. Critical bandwidth was taken as the frequency separation between noise bands at which masked tonal threshold began to change and was found to increase fairly regularly as the spectrum level of the noise increased from 30-60 db SPL. However, the data at 60 db SPL may have been influenced a 2 and 4 kc/s by the detection of aural distortion products. The suggestion was made that when signal frequency is outside the spectral limits of the masker, critical bandwidth widens as masker level is raised; however, when signal frequency is within the spectral limits of the masker (as with a continuous noise wit no notches), critical bandwidth remains unchanged up to 80 bd SPL.

Adult↗