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PubMedDate not supplied

Loudness and the acoustic reflex: cochlear-impaired listeners.

The relationships among most comfortable listening level (MCL), loudness discomfort level, and the acoustic reflex (AR) to speech were studied on cochlear-impaired listeners using earphones and sound field conditions. Recorded sentence materials were presented monaurally in quiet and in the sound field in the presence of 55 dB SPL cafeteria noise. Both unaided and aided sound field testing were done. The results indicated that the MCL and AR fell at approximately the same intensities under all test conditions, whereas the LDL occurred at approximately 18 dB higher intensity. The MCL was elevated by the presence of noise, whereas the AR remained invariant. Also, the AR occurred below the level predicted by the loudness function. The results tend to indicate that although the AR is highly correlated with MCL in cochlear-impaired listeners a cause and effect relationship may not exist.

Adolescent↗
PubMedDate not supplied

An acoustic reflex technique of establishing hearing aid settings.

An acoustic reflex method of establishing hearing aid gain settings for most comfortable loudness was tested. Forty hearing-aid users were examined to determine relationships among MCL, loudness discomfort level, and the contralateral acoustic reflex to speech, under unaided and aided conditions. Results indicate that a simple 2-part rule results in amplification to most comfortable loudness for 76% of subjects. Implications for establishing hearing aid saturation sound pressure level settings are discussed.

Adolescent↗
PubMed1980

[Binaural summation of the ipsilateral and contralateral acoustic stapedius reflex (author's transl)].

The binaural summation of the simultaneous contra- and ipsilateral acoustic stapedius reflexes was examined in 20 normal-hearing patients. In these patients, the effect of summation was most pronounced with subthreshold intensities. A contralateral reflex was increased by ipsilateral intensities 8 db below threshold. A reflex could also be elicited by binaural intensities which were contra- and ipsilaterally 4 db below threshold. As a result of our studies, we recommend a revision of the definition of a positive Metz-recruitment. Because of possible binaural summation effects, the absolute value of the contralateral stapedius reflex threshold should not exceed 105 db HL in spite of possible sensorineural hearing loss.

Acoustic Impedance Tests↗
PubMedDate not supplied

Hearing loss in rats first exposed to toluene as weanlings or as young adults.

Male Fischer-344 rats were exposed by inhalation to 1200 ppm toluene (14 hr/day, 7 days/week for 5 weeks) beginning just after weaning or as young adults. During the fifth week of exposure, they were trained to perform a multisensory conditioned pole-climb avoidance response (CAR) task using a 4-kHz tone, a change in the intensity of the test chamber light, or a nonaversive current on the grill floor as the stimuli. When tested the week after the exposures ended, both groups of toluene-exposed rats were deficient in their performance of the CAR to a 20-kHz tone. This effect was significantly greater for the rats exposed beginning just after weaning than it was for the young adult rats. Subsequent behavioral and electrophysiologic audiometry confirmed the presence of a toluene-induced high-frequency hearing loss in both groups of rats with the more severe deficits occurring in the younger rats. Preliminary morphologic examinations revealed loss of, and/or damage to, hair cells in the basal turn of the cochlea of the younger toluene-exposed rats. These results confirm our earlier discovery that inhalation exposure to toluene causes hearing deficits in rats, and they indicate that young, prepubertal rats are more severely affected than older rats.

Age Factors↗
PubMed1984

Comfortable loudness levels for speech: effects of signal-to-noise ratios and instructions.

The effect of S/N from +20 to -10 db on loudness levels of connected discourse with or without background cafeteria noise was investigated for one set of instructions sampling the most comfortable loudness level (MCLL) and a second set sampling the upper limit of CLL. Normal young adults (N:16) showed no significant differences for either set of instructions in quiet or from 20 to 0 db S/N but mn MCLL was about 5 db lower at -10 db. Elderly hearing-aid wearers (N:10, mn age: 77 yrs) yielded mn differences across S/N of less than 5 db for either set of instructions. No data indicate that the speech CLL accurately predicts optimal hearing-aid gain, while the literature indicates that occasionally the desired maximum intelligibility frequently is not obtained at the MCLL. We question whether MCLL for speech justifies its measurement. A discussion is presented of the Comfort Level Method of adjusting gain in hearing-aid evaluations and a perhaps preferable Threshold Level Method in which the test stimulus is presented at a level corresponding to the predicted threshold and the aid's volume control is adjusted until S just perceives the signal.

Adult↗
PubMed1984

Hearing and vestibular abnormalities in primary fibrositis syndrome.

A prospective neurootological study of 30 cases of primary fibrositis syndrome (PFS) and 30 sex and age matched healthy volunteers was performed. Results showed that 70% of the PFS patients had decreased painful sound threshold, 40% hyperreactivity of perrotatory nystagmus without neurological or peripheral vestibular lesions, and 27% asymptomatic sensorineural hearing loss at low frequencies. Such abnormal data were not found in the matched controls. These findings suggest that otological problems may be part of the nonrheumatic features encountered in PFS.

Adult↗
PubMed1983

[Responses of neurons of the medial geniculate body in the cat to positive and negative intensity increments in noise signals].

73% of the cat internal geniculate body neurons responded with a phasic on-response to positive intensity increments of the white noise signal. 35% of the neurons responded with a phasic off-response to negative increments of the signal. At a constant rate of increment (6 dB), the amplitude and latency of the responses were found to depend on the level of the basis intensity. The amplitude dependence was rather irregular whereas the latency dependence was different in different neurons. Neurons were found which had the latencies of their on-responses augmenting with increase of the basis. The on- and off-responses revealed the ability of most neurons to single out the moment of intensity increment of a wide-band signal.

Animals↗
PubMed1983

Excursion size Bekesy tracings of continuous and interrupted tones at threshold and at most comfortable loudness in cochlear-impaired ears.

Bekesy fixed-frequency tracings at .5, 1, and 4 kc/s were obtained at THL and at MCL from 64 men with cochlear-impaired ears. Mean continuous- (C) and interrupted-tone (I) excursion sizes were compared within 4 hearing-level categories from mild to severe/profound. Mean I-tone excursions were comparable at THL and MCL, regardless of amount of loss or frequency, the majority of excursions between 5-15 db. Mean C-tone excursions at MCL were reduced to less than 5.5 db á value at HTL said by Bilger (1965) to be clinically significant in separating normal from pathological cochlear function], i.e., significantly more often than mean C-tone excursions at THL . Inspection of excursion size at MMCL appears to have diagnostic value.

Audiometry↗
PubMed1983

Temporal summation in normally and abnormally hearing chinchillas.

Young adult monauralized chinchillas (N:5) were conditioned to cross a barrier in response to 7 pure tones from .5-4 kc/s. Tone bursts were either 20- or 500-msec long. Individual S's yielded threshold data for the longer duration comparable to published norms. Group mn difference between thresholds at 20- vs 500-msec durations [i.e., temporal summation (TS)] was 7 db, or 4.7 db less than TS reported for normal chinchillas reported by Wall et al (J. Aud. Res., 1981, 21, 29-37) and others. One S yielded no TS. After exposure for 4 hrs to a 2-kc/s tone at 120 db SPL, group mn thresholds for the 20-msec tones were only 1 db poorer than those for 500-msec tones (i.e., negligible TS). TS is clearly altered in noise-induced hearing loss.

Acoustic Stimulation↗
PubMed1984

[Sound pressure isopotential levels for the microphonic potential of the internal ear].

The amplitude of gross microphonic potential of guinea pigs was used for output regulation of the generator of sinusoidal and narrow-band noise signals at continuous changing of frequencies. Thus isopotential contours of sound pressure levels (SPL) were obtained. The dynamics of the isopotential SPL on different levels within the range of 50-20 000 Hz, is described.

Acoustic Stimulation↗
PubMed1982

The SISI test: a review. Part II.

This is the second of two papers reviewing the SISI test. In this paper we discuss modifications of SISI, and the effects of contralateral masking and tone decay. We also compare SISI to other psychoacoustic site of lesion tests and discuss the implications of the results obtained in SISI. The following conclusions are drawn: (1) SISI performed at high levels appears powerful in detecting retrocochlear impairments. (2) Contralateral masking is advisable when cross-hearing cues are present. The masking level should be minimized and a noise level 10 dB below the level of the contralaterilized tone provides sufficient masking. (3) SISI remains valid despite the presence of tone decay. (4) High SISI scores in cochlearly impaired listeners do not indicate improved auditory acuity.

Audiometry, Pure-Tone↗
PubMedDate not supplied

Psychoelectric measurements and results from cochlear implant patients.

Psychoelectric experiments, including threshold, uncomfortable loudness level, loudness growth and frequency discrimination were performed with six cochlear implant patients. All subjects used a single-channel transdermal induction coil implant system. Stimuli were presented directly to the external induction coil and not through a signal processing device. A method is reported in which current at the electrode is derived from voltage measures at the external coil. The derived thresholds were on the order of 1 to 120 microA peak-to-peak and are similar to those reported by other investigators. Loudness growth was more rapid for implant patients, being over twice that of normal listeners. Frequency difference limens were determined using both analog and 16 kHz amplitude modulated signals. Frequency discrimination was better with the analog system than with the 16 kHz amplitude modulated system. In general, below 100 Hz the patients' difference limens were essentially normal, but rapidly deteriorated until at approximately 600 Hz there was little frequency discrimination.

Cochlear Implants↗
PubMedDate not supplied

Otopathological findings in a patient with bilateral cochlear implants.

The death in 1976 of a patient who had a multiple-electrode cochlear implant in one cochlea and a single-electrode cochlear implant in the other provided a unique opportunity for both clinical and histological study of the effects of such implants in a human an subject. The patient was 68 years old at the time of his death. In 1969, at the age of 61, and after 11 years of profound deafness, apparently as a result of lues, the patient was implanted on the left side with a hard-wired 5-wire multiple-electrode cochlear implant. Five years later, his right side was implanted with a single-electrode induction coil cochlear implant. Audiological and psychoacoustic studies were performed by a number of investigators. The results are reviewed. Following the patient's death, his temporal bones were obtained and examined using microdissection techniques followed by serial sectioning. The histological findings are described.

Aged↗

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