The interaural level difference (ILD) is a robust indicator of sound source azimuth, and human ILD sensitivity persists under conditions that degrade normally-dominant interaural time difference (ITD) cues. Nonetheless, ILD sensitivity varies somewhat with both stimulus frequency and interaural correlation (coherence). To further investigate the combined binaural perceptual influence of these variables, the present study assessed ILD sensitivity at frequencies 250–4000 Hz using stimuli of varied interaural correlation. In the first of two experiments, ILD discrimination thresholds were modestly elevated, and subjective lateralization slightly reduced, for both half-correlated and uncorrelated narrowband noise tokens relative to correlated tokens. Different from thresholds in the correlated condition, which were worst at 1000 Hz [Grantham, D.W. (1984). J. Acoust. Soc. Am. 75, 1191–1194], thresholds in the decorrelated conditions were independent of frequency. However, intrinsic envelope fluctuations in narrowband stimuli caused moment-to-moment variation of the nominal ILD, complicating interpretation of measured thresholds. Thus, a second experiment employed low-fluctuation noise tokens, revealing a clear effect of interaural decoherence per se that was strongly frequency-dependent, decreasing in magnitude from low to high frequencies. Measurements are consistent with known integration times in ILD-sensitive neurons and also suggest persistent influences of covert ITD cues in putative “ILD” tasks.

中文翻译：

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耳间退相干对跨频率的耳间电平差异敏感度的影响

耳间电平差 (ILD) 是声源方位角的可靠指标，并且人类 ILD 灵敏度在降低通常占优势的耳间时间差 (ITD) 线索的条件下仍然存在。尽管如此，ILD 敏感性会随着刺激频率和耳间相关性（连贯性）而有所不同。为了进一步研究这些变量的组合双耳感知影响，本研究使用不同耳间相关性的刺激评估了 250-4000 Hz 频率下的 ILD 敏感性。在两个实验的第一个中，相对于相关标记，对于半相关和不相关的窄带噪声标记，ILD 辨别阈值适度升高，主观偏侧化略有降低。与相关条件下的阈值不同，在 1000 Hz 时最差 [Grantham, DW （1984 年）。J. 声学。社会党。是。75 , 1191–1194]，去相关条件下的阈值与频率无关。然而，窄带刺激的内在包络波动导致标称 ILD 的瞬间变化，使测量阈值的解释复杂化。因此，第二个实验采用了低波动噪声标记，揭示了耳间退相干本身的明显影响，这种影响本身强烈依赖于频率，幅度从低频到高频递减。测量结果与 ILD 敏感神经元中已知的整合时间一致，并且还表明隐蔽 ITD 线索在假定的“ILD”任务中的持续影响。