Biomedical subjects

K A Beauchaine

Publications and source records attributed to K A Beauchaine.

14 recordsLinked to original sources

PubMed1989

High-frequency audiometry: test reliability and procedural considerations.

This study compared the reliability of a recently developed high-frequency audiometer (HFA) [Stevens et al., J. Acoust. Soc. Am. 81, 470-484 (1987)] with a less complicated system that uses supraaural earphones (Koss system). The new approach permits calibration on an individual basis, making it possible to express thresholds at high frequencies in dB SPL. Data obtained from 50 normal-hearing subjects, ranging in age from 10-60 years, were used to evaluate the effects on reliability of threshold variance, earpiece/earphone fitting variance, and the variance associated with the HFA calibration process. Without earpiece/earphone replacement, the reliability of thresholds for the two systems is similar. With replacement, the HFA showed poorer reliability than the Koss system above 11 kHz, largely due to errors in estimating the calibration function. HFA reliability is greater for subjects with valid calibration functions over the entire frequency range. When average correction factors are applied to the Koss data in an effort to convert threshold estimates to dB SPL, individual transfer functions are not represented accurately. Thus the benefit of being able to express thresholds at high frequencies in dB SPL must be weighed against the additional source of variability introduced by the HFA calibration process.

Adolescent↗

PubMed1989

Normative thresholds in the 8- to 20-kHz range as a function of age.

Using a prototype high-frequency audiometer, auditory thresholds in the 8- to 20-kHz range were obtained from 240 subjects ranging in age from 10-60 years. These measurements were obtained in interest of developing a normative database for frequencies above 8 kHz, and to evaluate intersubject variability as a function of age. An analysis of variance (ANOVA) revealed significant effects of frequency, age, and sex, and a significant frequency-by-age interaction. The largest changes in sensitivity with age occurred between 40 to 59 years. Below approximately 15 kHz, the intersubject variability of threshold estimates increased as a function of both age and frequency. Further analysis revealed that the age-related changes in variability were related to absolute thresholds rather than to age per se. When data are converted to dB HL (relative to the youngest group tested), the region of maximum hearing loss shifts to lower frequencies with increasing age, and threshold shifts with age are greatest in the 13- to 17-kHz range.

Adolescent↗

PubMed1988

Auditory brainstem responses to tone bursts in normally hearing subjects.

Auditory brainstem responses were recorded from 20 normally hearing subjects using tone-burst stimuli that were gated with cosine-squared functions. Clear responses were observed over a wide range of frequencies and levels. These responses were highly reproducible within individual subjects and were reliably measured by two independent examiners. ABR thresholds were higher than behavioral thresholds for all frequencies, especially for lower frequencies. Intersubject variability also was greater for lower frequencies. Wave-V latencies decreased with increases in both frequency and level for frequencies from 250 to 8000 Hz and for levels from 20 to 100 dB SPL. The standard deviations seldom exceeded 10% of the mean wave-V latency for any combination of level and frequency. These latencies can be viewed as the sum of both a peripheral and a central component. Assuming that the central component is relatively independent of both frequency and level, changes of wave V latency must be related to peripheral factors, such as travel time along the cochlear partition, and to stimulus characteristics, such as rise time.

Acoustic Stimulation↗

PubMed1988

Auditory brain stem responses from graduates of an intensive care nursery using an insert earphone.

Auditory brain stem responses (ABR) were measured from graduates of an intensive care nursery using an insert earphone. Approximately 95% of all ears had click-evoked ABR thresholds of 30 dB nHL or less. Absolute latencies of waves I and V were within the range observed for a circumaural earphone, once the delay introduced by the insert earphone's sound delivery tube was taken into account. Finally, interpeak latency differences and interaural symmetry were comparable to values observed when a similar group of patients were tested with a circumaural earphone.

Audiometry, Evoked Response↗

PubMed1988

The reliability of auditory thresholds in the 8- to 20-kHz range using a prototype audiometer.

This study was designed to evaluate both intra- and intertester reliability of auditory thresholds in the 8- to 20-kHz range using a recently developed high-frequency audiometer [Stevens et al., J. Acoust. Soc. Am. 81, 470-484 (1987)]. With this device, signals from a high-frequency transducer are introduced into the ear canal via a plastic tube. A calibration function is calculated for each ear and used to estimate the sound-pressure level (SPL) at the tympanic membrane. Twenty normal-hearing listeners were tested four times, twice by each of two examiners. In the higher frequencies, accurate calibration functions could not be obtained for many subjects; in these cases, values extrapolated from lower frequencies were used to estimate SPL. Findings reveal that the standard error of measurement for both intra- and intertester measures increases as a function of frequency. Intertester variability was only slightly higher than intratester variability. In most cases, variability of threshold estimates in dB SPL was higher than that observed for the uncorrected attenuator settings. Exclusion of extrapolated values improved reliability substantially.

Adult↗

PubMed1987

Comparison of onset and steady-state responses of hearing aids: implications for use of the auditory brainstem response in the selection of hearing aids.

Input-output (I/O) functions of hearing aids were measured in response to a 2000-Hz tone burst, having 0.5 ms rise/fall time and 10 ms duration. I/O functions, measured with a hearing-aid analyzer, served as reference conditions. Hearing-aid outputs at onset and during the steady-state portion of the waveform differed; these differences often depended upon stimulus rate. The relation between onset and steady-state estimates of output were not always predictable from hearing-aid attack and release times. These findings indicate that the steady-state output limitation characteristics of hearing aids cannot be estimated from their onset responses. In turn, this suggests that ABR measurements may not provide accurate estimates of the compressive characteristics of hearing aids.

Acoustics↗

PubMed1987

Auditory brainstem responses from graduates of an intensive care nursery: normal patterns of response.

Auditory brainstem responses (ABR) were obtained from graduates of an intensive care nursery (ICN) when those babies were in stable physiological states and ready for hospital discharge. Intensity ranged from ABR threshold to 80 dB nHL, and all recordings were made in a sound-isolated chamber. The data reviewed here are from 585 babies having presumably normal hearing, based upon bilateral ABR thresholds of 30 dB nHL or less. To insure that estimates of population statistics were not biased by high correlations between ears, only the data from the left ears were used in most analyses. Larger correlations were observed between conceptional age (CA) and ABR latencies than between either gestational age (GA) or chronological age (CHA) and the same latencies. Data were grouped into six CA groups for further analyses. Distributions of all response-component latencies were similar in shape and depended upon CA, showing orderly decreases in latency with increasing age. None of these distributions differed significantly from normal, and they were well fitted by normal ogives. Thus, accurate estimates of percentiles can be obtained from the means and standard deviations. The results indicate that it is important to take CA into account when evaluating ABR latencies.

Audiometry, Evoked Response↗

PubMed1987

Auditory brain stem responses to high-frequency tone bursts in normal-hearing subjects.

ABR and behavioral thresholds and ABR latencies were measured from six normal-hearing subjects in response to tone bursts, having frequencies of 9,000 to 16,000 Hz. In general, ABR thresholds were higher than behavioral thresholds; however, the differences were typically less than those observed for lower frequencies. Wave V latency-intensity functions were less dependent on frequency for these stimuli than they were for lower frequency stimuli. This may be due to the fact that higher frequencies are represented over a very narrow area of the cochlea and that minor variability in the measurement of latencies might obscure small differences in latency as a function of frequency. In general, these data suggest that ABRs can be measured in response to high-frequency stimuli and that these measurements may have clinical utility, especially when monitoring ototoxic effects in difficult-to-test patients.

Acoustic Stimulation↗

PubMed1987

Comparison of Beyer DT48 and etymotic insert earphones: auditory brain stem response measurements.

Click-evoked auditory brain stem responses (ABRs) were measured using a Beyer DT48 circumaural earphone and an Etymotic ER-3A insert earphone in a group of normal-hearing subjects. Comparisons were made between time waveforms and amplitude spectra for the two transducers. ABR waveforms, latencies, and thresholds were compared for the two transducers. Click-evoked ABR and behavioral thresholds were comparable for the two earphones. In addition, absolute response-component latencies differed by an amount that was equivalent to the travel time introduced by the insert earphone's sound-delivery tube. Inter-peak latency differences were virtually identical. These findings suggest that the insert earphone is a viable transducer for clinical ABR evaluations. Further, a temporal correction may be all that is necessary to account for the difference between the insert earphone and the circumaural earphone if other characteristics of the transducers are similar.

Auditory Threshold↗

PubMed1986

Application of ABRs to the hearing-aid selection process: preliminary data.

This paper describes preliminary data on the use of click-evoked ABRs in the hearing aid selection process. Four normal-hearing and 4 hearing-impaired subjects were tested with a hearing aid set at three different frequency response settings. Estimates of gain were calculated using shifts in Wave V thresholds, shifts in Wave V latency-level functions, acoustic-reflex measurements, coupler gain measurements, and measurements of functional gain. Results suggest that the click-evoked ABR does not distinguish between differing amounts of low-frequency gain, although reasonable estimates of high-frequency gain appear possible. Also discussed are technical factors that must be considered when using the ABR in the hearing aid evaluation process.

Adult↗

PubMed1985

Auditory brainstem responses in a case of high-frequency conductive hearing loss.

Click-evoked auditory brainstem responses were measured in a patient with high-frequency conductive hearing loss. As is typical in cases of conductive hearing loss, Wave I latency was prolonged beyond normal limits. Interpeak latency differences were just below the lower limits of the normal range. The Wave V latency-intensity function, however, was abnormally steep. This pattern is explained by the hypothesis that the slope of the latency-intensity function is determined principally by the configuration of the hearing loss. In cases of high-frequency hearing loss (regardless of the etiology), the response may be dominated by more apical regions of the cochlea at lower intensities and thus have a longer latency.

Audiometry↗

PubMed1984

The effects of stimulus duration on ABR and behavioral thresholds.

ABR and behavioral thresholds were estimated as a function of stimulus duration for three normal and two hearing-impaired subjects. Stimuli were 2000-Hz tone bursts with 0.5-ms rise/fall times and durations ranging from 1 to 256 or 512 ms. For both groups of subjects, ABR thresholds were independent of stimulus duration. Normal subjects showed greater improvement in behavioral thresholds as a function of duration than did subjects with hearing losses. Thus, it appeared that ABR and behavioral thresholds were affected differently by changes in stimulus duration and that the magnitude of these differences could depend upon the presence of hearing loss. These data indicate that temporal integration may be one factor which makes comparisons between ABR and behavioral thresholds complicated. In the present study, the magnitude of hearing loss, measured by the ABR, would have been underestimated if normal behavioral thresholds for short-duration stimuli were used as the reference.

Auditory Pathways↗

PubMedDate not supplied

Some comparisons between auditory brain stem response thresholds, latencies, and the pure-tone audiogram.

Aspects of auditory brain stem responses (ABR) and pure-tone behavioral audiograms were compared in patients with cochlear hearing loss. Click-evoked ABR thresholds appeared to be related most closely to the audiometric thresholds at 2000 and 4000 Hz, with relatively poor agreement at either 1000 or 8000 Hz. These results were related to the amplitude spectrum of the eliciting stimulus. The slope of the wave V latency-intensity function appeared to be related to the configuration of the hearing loss. Patients with high-frequency sensorineural losses had steeper slopes than normal subjects, whereas patients with flat sensorineural losses had shallower slopes. These results were related to the principle that response latency is determined by the cochlear region that predominates the ABR for different stimulus intensities.

Acoustic Stimulation↗

PubMedDate not supplied

Vestibular findings in the deaf and hard of hearing.

One hundred sixty-six youngsters (3 to 19 years of age) with severe-to-profound hearing impairments underwent vestibular evaluations with electronystagmography as part of a comprehensive medical and psychoeducational test battery. Twenty-two percent of the children had unilateral or bilateral labyrinthine weakness in response to caloric stimulation, and 21% demonstrated spontaneous or positional nystagmus. The tandem Romberg test was most predictive of those patients with caloric labyrinthine weakness. The performance of mental alerting tasks (using sign language when appropriate) by the patients during testing proved essential in overcoming a marked tendency toward central suppression of nystagmus.

Adolescent↗