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Results for “Audiometry”

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At least 973 records · Page 54Linked to original sources
PubMed1976

Tone audiometry control of children treated for meningitis with large intravenous doses of ampicillin.

Thirty-seven children treated for bacterial meningitis with ampicillin in high doses were followed up with audiometric control. Defects were recorded in 6 cases. Two of these were ascribed to chronic otosalpingitis. In 4 patients with sensorineural hearing loss, 3 were unilateral, and in only one case was the damage bilateral. Even here there was a previous history of hearing loss. A suggested ototoxicity of ampicillin could not be confirmed.

Ampicillin↗
PubMed2006

Variation in the hearing sensitivity of a dolphin population determined through the use of evoked potential audiometry.

A portable electrophysiological data collection system was used to assess hearing in a captive population of bottlenose dolphins by recording auditory evoked potentials (AEPs). The AEP system used a transducer embedded in a suction cup to deliver amplitude modulated tones to the dolphin through the lower jaw. Evoked potentials were recorded noninvasively using surface electrodes. Adaptive procedures allowed hearing thresholds to be estimated from 10 to 150 kHz in a single ear in about 45 min. Hearing thresholds were measured in 42 bottlenose dolphins (28 male, 14 female), ranging in age from 4 to 47 years. Variations in hearing sensitivity with age and sex followed patterns seen in humans and terrestrial mammals: generally, within the population there was a progressive loss of high frequency hearing with age and an earlier onset of hearing loss in males than in females. Hearing loss generally occurred between the ages of 20 and 30, and all animals over the age of 27 had some degree of hearing loss. Two dolphins with profound hearing loss were found within the population. Aberrant hearing patterns were observed in related dolphins suggesting genetic links to hearing ability may exist.

Animals↗
PubMed1983

Reflex inhibition procedures for animal audiometry: a technique for assessing ototoxicity.

A procedure for making rapid audiometric assessments of animal subjects, based on the ability of weak stimuli to modify the strength of reflexes elicited by subsequently presented strong stimuli, is described. Pure-tone detection thresholds for rats and guinea pigs determined by this procedure are quite comparable to those determined by operant techniques, and are similarly sensitive to ototoxic insult. The procedure is also applicable to the assessment of suprathreshold sensory function, and offers advantages over commonly used procedures for assessing ototoxicity.

Animals↗
PubMed1987

Calibration of ear canals for audiometry at high frequencies.

A procedure is described for determining the absolute sound pressure at the inner end of the ear canal when a sound source is coupled to the ear, for frequencies in the range 8-20 kHz. The transducer that generates the sound is coupled to the ear canal through a lossy tube, yielding a source impedance that is approximately matched to the characteristic impedance of the ear canal. A small microphone is located in the coupling tube close to the entrance to the ear canal. Calibration is carried out by measuring the response at this microphone when an impulse is applied at the transducer. To estimate the sound pressure at the medial end of the ear canal, the Fourier transform of this impulse response is corrected by an all-pole function in which the poles are estimated from the minima in this Fourier transform. Data on individual ear canals are presented in terms of gain functions relating the sound pressure at the medial end of the ear canal to the sound pressure when the coupling tube is blocked. The average gain function for a group of adult ears increases from 2 to 12 dB over the frequency range 8-20 kHz, in rough agreement with data from ear-canal models. Possible sources of error in the calibration procedure are discussed.

Acoustics↗
PubMed1988

Sensory threshold estimation from a continuously graded response produced by reflex modification audiometry.

This article describes the use of reflex modification to determine sensory detection thresholds. The method is based upon the finding that low-intensity sensory stimuli presented shortly before a reflex eliciting stimulus are able to modify the amplitude of the reflex. The extent of such modification is related to the intensity of the initial low-intensity stimulus. In contrast to earlier reported procedures for threshold estimation, the method described in this article consists of fitting a smooth function to the relationship between startle response amplitude and the intensity of the inhibiting stimulus. The method entails fitting a cubic spline function to the medians of the square-root reflex amplitude at each prestimulus intensity. The resulting audiometric curves closely approximate audiometric data obtained from traditional operant methods both in sensitivity and shape. Parametric data are also presented that allow for optimizing stimulus presentation so as to obtain reliable thresholds using a minimal number of test trials. The procedures developed in this article may prove useful in other situations involving the estimation of a threshold effect from a continuously graded response.

Animals↗