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R A Butler

Publications and source records attributed to R A Butler.

53 records · Page 3Linked to original sources
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The spatial attributes of stimulus frequency in the median sagittal plane and their role in sound localization.

Stimulus cues used to locate sounds in the median sagittal plane were investigated. Listeners first were required to report the location of noise bands 1.0 kHz wide whose center frequencies ranged from 4.0 through 14.0 kHz. It was found that the apparent locations of the stimuli depended on their frequency compositions, not their places of origin. As the center frequency was increased from 4.0 to about 12.0 kHz, the apparent location of the sound moved from in front of the subject to the rear. Then, at center frequencies of around 13.0 kHz, the sounds again appeared to come from the front. The authors infer that different frequency regions within the sound's spectrum possess specific spatial referents along the median sagittal plane. When the bandwidth was increased to 4.0 kHz, listeners could locate the stimuli with reasonable proficiency only for the sectors of the median sagittal plane that were represented by the spatial referents inherent in the frequency composition of the stimulus. Finally, a stimulus comprising all audible frequencies above 4.0 kHz could be located proficiently, and it is concluded that this sound, unlike the others, contained all spatial referents for the median sagittal plane, hence the superior performance on the localization task.

Acoustic Stimulation↗
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An evoked response study of the first-order difference tone in man.

The amplitude of the N1-P2 component of a response evoked by a 250 Hz test stimulus presented once each 5 sec was measured. Interposed at a rate of one per sec were either 1) a 4000 Hz tone, 2) a 4000 Hz and a 4250 Hz tone presented simultaneously which generated within the ear an audible 250 Hz difference tone, or 3) a 250 Hz tone. The results indicated that the N1-P2 component when preceded by the 4000 Hz plus 4250 Hz stimulus pair was larger than when preceded by a 250 Hz tone, but smaller than when preceded by a 4000 Hz tome. Apparently the processing of the difference tone is unlike that of a sinusoid of the same frequency or that of a high frequency sinusoid which participated in the generation of the difference tone. Parallel electrophysiological data from cochlear recordings are discussed.

Acoustic Stimulation↗