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Biomedical subjects

T A Hamill

Publications and source records attributed to T A Hamill.

6 recordsLinked to original sources
PubMed1995

Differences in localization ability in cases of right versus left unilateral simulated conductive hearing loss.

The purpose of this study was to determine whether localization errors were greater in cases of right ear unilateral simulated conductive loss, as compared to left ear simulated conductive loss of the same degree and configuration. Thirty adults were asked to localize a 3-kHz warbled pure tone with their left and right ears alternately occluded with an earplug. Significantly greater localization difficulty was found when the right ear was occluded. The average error was 58 degrees with the left ear plugged and 64 degrees when the right ear was occluded, which approximates the 65-degree average error that would have resulted from random guessing. This suggests that short-term conductive losses result in unusually poor localization ability, which is worse if the right ear is affected.

Adolescent↗
PubMed1992

Threshold estimation using the "chained stimuli" auditory brain stem response technique.

The chained stimuli ABR method, which allows acquisition of data for a seven-point latency-intensity function for both ears in approximately 35 min, is described. Testing of 22 ears with a simulated conductive loss, and 20 ears with sensorineural impairment, indicates that the chained stimuli method provides equivalent threshold estimates to that obtained with the conventional ABR measurement technique.

Acoustic Impedance Tests↗
PubMed1992

Frequency response differences of four gain-equalized hearing aid prescription formulae.

The relative differences between the NAL, Berger, Lybarger und POGO hearing aid prescriptions were evaluated using 8 hypothetical audiograms and 81 actual hearing loss cases. The gains of the prescriptions were equalized, making the prescriptions maximally similar, as would presumably occur when the aids are worn. Statistically significant differences in the frequency responses of the prescriptions were found, with up to 17 dB gain difference observed; however, the gain differences at any given frequency were generally less than 8 dB. Sharply sloping hearing losses had the greatest differences between prescriptions. The NAL and Berger prescriptions were most disparate, while POGO and Lybarger were most similar. As large differences in prescribed gain are rare, research into the relevance of such small differences in frequency response is advocated as a precursor to study of the optimal prescription formula.

Ear↗
PubMed1991

Rapid threshold estimation using the "chained-stimuli" technique for auditory brain stem response measurement.

The "chained-stimuli" technique for rapid auditory brain stem response (ABR) threshold estimation involves lengthening the averaging time window and presenting a series ("chain") of click stimuli. Each stimulus chain contains, in addition to a silent interval, click stimuli of 10, 20, 30, 40, 50, 60, and 70 dB nHL that are separated by 10 msec intervals. Using this method, the single averaged response to the chained-stimulus contains up to seven individual ABRs. The responses elicited by each level of click stimulus within the chain can be analyzed separately. In this study, chained-stimuli ABR threshold estimations for normal hearers were essentially equivalent to those obtained using an automated conventional ABR method. The data for a seven point latency-intensity function using the chained-stimuli technique were obtained in a mean time of only 8 min per ear.

Acoustic Stimulation↗
PubMed1986

The relationship of pulsed, continuous, and warble extended-high frequency thresholds.

The relationship among pulsed, continuous and warble tone 10, 12, 14, and 16 kHz thresholds of six normal hearing young adults was studied. It was found that pulsed and continuous tones elicited essentially equivalent thresholds at all frequencies tested. Warble tone thresholds were markedly better than unmodulated thresholds at 14 and 16 kHz. This threshold discrepancy is believed to be attributable to hearing the lowest frequency components of the warble tone when a sloping audiometric configuration exists. The audiologist is cautioned against using warble tones in extended-high frequency testing.

Adult↗