Biomedical subjects

A Miśkiewicz

Publications and source records attributed to A Miśkiewicz.

3 recordsLinked to original sources

PubMed1997

Loudness adaptation and excitation patterns: effects of frequency and level.

Simple loudness adaptation for pure tones was measured at frequencies from 0.125 to 16 kHz and at sensation levels from 5 to 60 dB. Sixteen young listeners with normal hearing participated in four experiments. Most of the loudness measurements were obtained by the method of successive magnitude estimation; some were also obtained by loudness matching. The two indices of loudness adaptation gave similar results. At all frequencies, loudness adaptation increased as sensation level decreased. After 6 min, average loudness declined at most frequencies by about 20% at 40-dB sensation level (SL) and by between 70% and almost 100% at 5-dB SL. Adaptation also increased with increasing frequency, and was especially marked at 16 kHz, where loudness declined more than 60% at a sensation level as high as 40 dB. Most of the adaptation occurred usually within the first 3 min of exposure, but loudness continued to diminish at a slower rate up to around 6 min. The dependence of loudness adaptation on frequency and level can be largely accounted for by the restricted-excitation-pattern hypothesis. Adaptation is assumed to take place when excitation is restricted to a narrow region of the cochlea. This hypothesis is supported by a quantitative analysis based on excitation patterns derived from measurements of masking.

Adolescent↗

PubMed1994

Auditory facilitation: procedural or sensory effect?

A few studies have reported that, under certain conditions, thresholds following exposure to a sound may be lower than those measured without prior stimulation. For example, Rubin [J. Acoust. Soc. Am. 32, 670-681 (1960)] found a 7-dB negative shift in threshold, for a 20-ms tone presented 160 ms after termination of a low-level cue tone. This "auditory facilitation" was obtained with an up-and-down psychophysical method. In the present study, auditory facilitation was reexamined using an adaptive, two-interval, two-alternative-forced-choice (2I, 2AFC) procedure. Thresholds were measured for 20-ms tones at 1 and 5 kHz, preceded by a 15-dB SL 80-ms cue tone of the same frequency. In addition, thresholds were measured with the cue absent. The results show that thresholds can be lower in the presence of the cue than in its absence, but the effect averages 0.5 dB or less and seems to be independent of cue-signal delay between 80 and 640 ms. Because this finding contrasts with the 7-dB facilitation, which Rubin obtained using an up-and-down method, part of his experiment was replicated and the results were essentially the same as his. The failure to find a pronounced facilitation effect with a 2I, 2AFC procedure indicates that the poststimulatory lowering of threshold found by Rubin primarily resulted from biases and criterion shifts.

Auditory Perception↗

PubMed1993

Loudness adaptation at high frequencies.

Loudness adaptation was measured for pure tones at 4, 12, 14, and 16 kHz. In three experiments, a total of 87 young listeners judged--by the method of successive magnitude estimation--the loudness of the tones over a 6-min exposure period. Thresholds were measured by an adaptive 2IFC procedure. Although earlier measurements had shown that adaptation near threshold increases with frequency, these new data reveal that the increase is especially marked at higher sensation levels. Thus, at 40 dB SL, over a 6-min period loudness declined by 18% at 4 kHz and by 94% at 16 kHz. Moreover, the 4-kHz tone remained audible for all listeners throughout the 6-min exposure period whereas the 16-kHz tone became inaudible for two-thirds of them by the end of the exposure period. Listeners with relatively low thresholds (< 50 dB SPL) at 16 kHz showed much less adaptation at 14 kHz than at 16 kHz and much less than listeners with relatively high thresholds (> 50 dB SPL) at 16 kHz; this latter group showed strong adaptation at 14 kHz. The marked loudness adaptation of steady tones at very high frequencies and relatively high sensation levels is associated with a restricted spread of excitation in the auditory system resulting from the steep rise of the threshold curve at the highest audible frequencies.

Acoustic Stimulation↗