Rakerd B, Hartmann W M
J Acoust Soc Am. 1986 Dec;80(6):1695-706. doi: 10.1121/1.394282.
The steady-state sound field of a sine tone does not provide useful localization information in a room. Nevertheless, listeners can localize a sine tone in a room if it has an onset transient which allows the precedence effect to operate. In the present study, we made a quantitative assessment of onsets and the precedence effect by systematically varying onset duration from 0 s (impulsive), where the precedence effect is maximal, to 5 s, where there is no precedence effect at all. We also assessed listeners' sensitivity to the steady-state sound field under impulsive conditions by varying the total duration of tone pulses. Our experiments were conducted in a room with a single acoustical reflection having various directions and delays, and in an anechoic room. The results for tones of various frequencies (500 and 2000 Hz) and sound-pressure levels (65 and 40 dBA) indicate the following: Localization in rooms is facilitated by onsets even if the onsets are as long as 100 ms. The facilitation depends upon the peak intensity of the tone, as well as the onset duration, suggesting that onset rate is critical for the precedence effect; our results are most consistent with rate expressed as an increase in sound pressure per unit time. The facilitation also depends upon the reflection delay time for a room; gradual onsets take on much more importance for the precedence effect in rooms with long delays. As onsets begin to lose their effectiveness listeners become increasingly "misdirected" by invalid cues in the steady-state sound field. The pattern of misdirection suggests a perceptual averaging of cues over an interval more than an order of magnitude longer than previous estimates of the summation window for the precedence effect. The pattern of misdirection varies with the frequency of a tone, due to frequency-dependent interference effects in a room, but it is independent of signal level. Localization of an impulsive sine tone in rooms is very insensitive to the pulse duration; this suggests that binaural inhibition models of the precedence effect must be supplemented by an evaluative component that we term the "plausibility hypothesis."
正弦音调的稳态声场在房间内并不能提供有用的定位信息。然而，如果正弦音调有起始瞬态，使得优先效应起作用，听众就能在房间内对其进行定位。在本研究中，我们通过系统地改变起始持续时间（从0秒（脉冲式），此时优先效应最大，到5秒，此时完全没有优先效应），对起始和优先效应进行了定量评估。我们还通过改变音调脉冲的总持续时间，评估了听众在脉冲条件下对稳态声场的敏感度。我们的实验在一个有单一声学反射、具有不同方向和延迟的房间以及一个消声室中进行。各种频率（500和2000赫兹）和声压级（65和40分贝声级）音调的实验结果表明：即使起始时间长达100毫秒，起始也有助于在房间内进行定位。这种促进作用取决于音调的峰值强度以及起始持续时间，这表明起始速率对优先效应至关重要；我们的结果与以单位时间内声压增加来表示的速率最为一致。这种促进作用还取决于房间的反射延迟时间；对于延迟较长的房间，逐渐的起始对于优先效应更为重要。随着起始开始失去其有效性，听众会越来越多地被稳态声场中的无效线索“误导”。这种误导模式表明，在比先前对优先效应求和窗口估计长一个数量级以上的时间间隔内，线索存在感知平均。由于房间内频率相关的干扰效应，误导模式随音调频率而变化，但与信号电平无关。在房间内对脉冲正弦音调的定位对脉冲持续时间非常不敏感；这表明优先效应的双耳抑制模型必须辅以一个我们称为“合理性假设”的评估成分。
