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B R Shelton

Publications and source records attributed to B R Shelton.

9 recordsLinked to original sources
PubMed1991

Counterintuitive reversals in lateralization using rectangularly modulated noise.

Listeners were required to detect an interaural delay of 37.5 microseconds in the modulation envelope of a pulse-modulated noise. The noise carrier had a bandwidth of 1000 Hz and a center frequency (fc) that varied from 550-9600 Hz. The modulation frequency was either 250, 500, or 1000 Hz and the pulse widths were either 100, 200, or 400 microseconds. For certain combinations of fc and pulse widths, unexpected results occurred when the side of the perceived image did not agree with the side stimulated first. Lateralizations of these stimuli were found to oscillate from the leading side to the lagging depending on the number of cycles of the carrier falling within a single pulse, seemingly indicating the importance of the stimulus' fine structure. Furthermore, conditions that either limited the bandwidth of the stimuli or masked portions of its spectrum show that the oscillations depended on information in the low-frequency regions. A cross-correlation model that emphasizes both the positive and negative peaks in the cross-correlations functions is shown to describe the basic phenomena.

Attention↗
PubMed1981

Psychophysical tuning curves independent of signal level.

Psychophysical tuning curves were obtained for three subjects in a forward masking paradigm, with signal levels of 21, 30, and 50 dB SPL at 1000 Hz and 30, 40, and 50 dB SPL with a 3000-Hz signal. All tuning curves were measured in quiet and with a background noise adjusted to produce a constant signal-to-noise ratio of E/N0 = 16 dB. The results indicated that the tuning curves obtained in quite change shape with increasing signal level, whereas the shapes of tuning curves measured in noise are the same at all signal levels. A control condition demonstrates that only signal energy in a narrow band near the signal frequency is useful in detecting the signal. This control along with the invariance of tuning curve shape with signal level support the interpretation that the broadening of tuning curves with increased signal level, observed when the signals are presented in quiet, is caused by the presence of off-frequency components.

Acoustic Stimulation↗
PubMed1979

Some published data on auditory localization reanalyzed within the framework of a model proposed by Searle, Braida, Davis, and Colburn.

The model for auditory localization proposed by Searle et al (J. Acoust. Soc. Am., 1976, 60, 1164-1175) was predicated on several assumptions and on data from restricted sound source loci. For example, only those studies were included using frontal-median plane sources and Ss with restrained head movements. The authors noted, however, that the model's generality needed to be tested by use of paradigms that gathered data from positions all around the S, and with data in which variables other than those accounted for by the model were utilized. Two studies (Gatehouse and Cox, J. Audit. Res., 1972, 12, 179-183, Gatehouse, J. Audit. Res., 1976, 16, 265-273) had required Ss to identify the position of a loudspeaker in both azimuth and elevation stimultaneously from a matrix of as many as 60 loci, but data had been reported only in per cent correct. The present paper offers a reanalysis of these data using average error in the spherical coordinates system of the model. Average-error analysis proved to be a relatively powerful tool, confirming the model to that extent. For example, a significant superiority of binaural over monaural performance in vertical plane localization was extracted from the data. Again, it could be shown that broadband noise, as compared with pure tones, provides useful binaural information in both the horizontal and vertical planes. Use of the model in studies of complex localization tasks may answer some unresolved issues and inconsistencies found in the general localization literature.

Analysis of Variance↗
PubMed1978

Two determinants of localization acuity in the horizontal plane.

An attempt was made to extend the auditory localization model of Searle, Braida, Davis, and Colburn [J. Acoust. Soc. Am. 60, 1164-1175 (1976)] to regions beyond the fontal horizontal plane. On the basis of two experiments, it appears that the assumption of acuity independent of angle is not valid for these more extensive regions, although the distribution of error magnitude can be accounted for by a span-specific unitary acuity. However, the assertion by the same authors that acuity is partially determined by the angular size of the speaker span was substantiated by direct experimental test. The results confirm the initial suggestion of Searle et al. that a complete account of the sound localization process must include both span and angular dependencies of acuity, and indicate average error to be a promising measurement technique in resolving this particular problem.

Auditory Perception↗