Jennifer J. Lentz
Dept. of Bioeng., Univ. of Pennsylvania, Philadelphia, PA 19103
Virginia M. Richards
Univ. of Pennsylvania, Philadelphia, PA 19103
The ability of observers to detect changes in interaural intensity difference across frequencies was tested using multitone complexes. The tonal components ranged in frequency from 200 to 5000 Hz, with amplitudes randomly drawn from a Gaussian distribution having a mean of 60 dB SPL and a given variance. For the standard stimulus, variance was zero, providing equal-amplitude tones. The signal stimulus had a nonzero variance. Because independently drawn signal stimuli were presented to the left and right ears, interaural level differences varied randomly across frequency. Percent correct signal detections were measured as a function of the variance of the signal stimulus. To encourage discrimination based on the pattern of interaural level differences across frequency rather than the change from diotic (standard) to dichotic (standard+signal), the overall levels of the stimuli presented to each ear were independently chosen from a 7-dB range. Because standard and standard+signal power spectra differed, monaural cues to the presence of the signal were available. Thus psychometric functions were separately obtained using the same signal stimulus at both ears. Results indicate that the detectability of changes in interaural level differences across frequency is nearly the same as the detectability of changes in power spectra for diotic presentations. [Work funded by NIH.]