Department of Otolaryngology, University of California, Irvine, CA 92697-5310, USA.
Adv Exp Med Biol. 2013;787:491-9. doi: 10.1007/978-1-4614-1590-9_54.
In a complex auditory scene, location in space is one of several acoustic features that permit listeners to segregate competing sequences of sounds into discrete perceptual streams. Nevertheless, the spatial acuity of stream segregation is unknown. Moreover, it is not clear whether this is really a spatial effect or whether it reflects a binaural process that only indirectly involves space. We employed "rhythmic masking release" as an objective measure of spatial stream segregation. That task revealed spatial acuity nearly as fine as listeners' discriminations of static locations (i.e., their minimum audible angles). Tests using low-pass, high-pass, and varying-level conditions in the horizontal dimension demonstrated that binaural difference cues provide finer acuity than does any monaural cue and that low-frequency interaural delay cues give finer acuity than do high-frequency interaural level differences. Surprisingly, stream segregation in the vertical dimension, where binaural difference cues are negligible, could be nearly as acute as that in the horizontal dimension. The results show a common spatial underpinning to performance. Nevertheless, a dissociation across conditions between localization acuity and masking-release thresholds suggests that spatial stream segregation is accomplished by brain systems discrete from those responsible for sound-localization judgments.
在复杂的听觉场景中，空间位置是允许听众将竞争的声音序列分离成离散感知流的几个声学特征之一。然而，流分离的空间锐度是未知的。此外，目前尚不清楚这是否真的是一种空间效应，还是反映了仅间接涉及空间的双耳过程。我们采用“节奏掩蔽释放”作为空间流分离的客观测量指标。该任务揭示了几乎与听众静态位置辨别（即最小可听角）一样精细的空间锐度。在水平维度上使用低通、高通和变化水平条件进行的测试表明，双耳差异线索提供的锐度比任何单耳线索都要精细，而低频的耳间延迟线索提供的锐度比高频的耳间水平差异线索更精细。令人惊讶的是，在垂直维度上，双耳差异线索可以忽略不计，流分离的锐度几乎与水平维度一样高。结果表明，性能具有共同的空间基础。然而，在条件之间，定位锐度和掩蔽释放阈值之间存在分离，这表明空间流分离是由大脑系统完成的，与负责声音定位判断的系统不同。
