This study investigated binaural detection of tonal targets (500 Hz) using sets of individual masker waveforms with two different bandwidths. Previous studies of binaural detection with wideband noise maskers show that responses to individual noise waveforms are correlated between diotic (N0S0) and dichotic (N0S(pi)) conditions [Gilkey et al., J. Acoust. Soc. Am. 78, 1207-1219 (1985)]; however, results for narrowband maskers are not correlated across interaural configurations [Isabelle and Colburn, J. Acoust. Soc. Am. 89, 352-359 (1991)]. This study was designed to allow direct comparison, in detail, of responses across bandwidths and interaural configurations. Subjects were tested on a binaural detection task using both narrowband (100-Hz bandwidth) and wideband (100 Hz to 3 kHz) noise maskers that had identical spectral components in the 100-Hz frequency band surrounding the tone frequency. The results of this study were consistent with the previous studies: N0S0 and N0S(pi) responses were more strongly correlated for wideband maskers than for narrowband maskers. Differences in the results for these two bandwidths suggest that binaural detection is not determined solely by the masker spectrum within the critical band centered on the target frequency, but rather that remote frequencies must be included in the analysis and modeling of binaural detection with wideband maskers. Results across the set of individual noises obtained with the fixed-level testing were comparable to those obtained with a tracking procedure which was similar to the procedure used in a companion study of rabbit subjects [Zheng et al., J. Acoust. Soc. Am. 111, 346-356 (2002)].

Binaural detection with narrowband and wideband noise maskers was examined by using a Pavlovian-conditioned eyeblink response in rabbits. The target was a tone at 500 Hz, and the maskers were ten individual noise samples having one of two bandwidths, 200 Hz (410 Hz to 610 Hz) or 2900 Hz (100 Hz to 3 kHz). The narrowband noise maskers were created by filtering the wideband noise maskers such that the two sets of maskers had identical spectra in the 200-Hz frequency region surrounding the tone. The responses across the set of noise maskers were compared across bandwidths and across interaural configurations (N0S0 and N0S(pi)). Responses across the set of noise waveforms were not strongly correlated across bandwidths; this result is inconsistent with models for binaural detection that depend only upon the narrow band of energy centered at the frequency of the target tone. Responses were correlated across interaural configurations for the wideband masker condition, but not for the narrowband masker. All of these results were consistent with the companion study of human listeners [Evilsizer et al., J. Acoust. Soc. Am. 111, 336-345 (2002)] and with the results of human studies of binaural detection that used only wideband [Gilkey et al., J. Acoust. Soc. Am. 78, 1207-1219 (1985)] or narrowband [Isabelle and Colburn, J. Acoust. Soc. Am. 89, 352-259 (1991)] individual noise maskers.

A Pavlovian conditioned eyeblink response in rabbits (Oryctolagus cuniculus) was used to study psychoacoustical phenomena previously demonstrated in human listeners and other animals. This article contains the results of a tone-in-noise detection study to examine 2 psychoacoustical phenomena in rabbit and in human listeners: (a) the binaural masking level difference (BMLD) and (b) differential performance across reproducible noise masker waveforms. The rabbits demonstrated a BMLD comparable in size to other species. Significant differences in performance across reproducible noise masker waveforms were seen in the rabbits. This performance was compared with the performance of human listeners using the same set of waveforms.

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