Centre for Applied Hearing Research, Department of Electrical Engineering, Technical University of Denmark, DTU Bygning 352, Orsteds Plads, 2800 Kgs. Lyngby, Denmark.
J Acoust Soc Am. 2013 Aug;134(2):1232-41. doi: 10.1121/1.4812264.
Real-world sound sources are usually perceived as externalized and thus properly localized in both direction and distance. This is largely due to (1) the acoustic filtering by the head, torso, and pinna, resulting in modifications of the signal spectrum and thereby a frequency-dependent shaping of interaural cues and (2) interaural cues provided by the reverberation inside an enclosed space. This study first investigated the effect of room reverberation on the spectro-temporal behavior of interaural level differences (ILDs) by analyzing dummy-head recordings of speech played at different distances in a standard listening room. Next, the effect of ILD fluctuations on the degree of externalization was investigated in a psychoacoustic experiment performed in the same listening room. Individual binaural impulse responses were used to simulate a distant sound source delivered via headphones. The ILDs were altered using a gammatone filterbank for analysis and resynthesis, where the envelopes of the left and right-ear signals were modified such that the naturally occurring fluctuations of the ILDs were restricted. This manipulation reduced the perceived degree of externalization. This was consistent with the analysis of short-term ILDs at different distances showing that a decreased distance to the sound source also reduced the ILD fluctuations.
真实世界的声源通常被感知为外部化的，因此在方向和距离上都能得到正确的定位。这主要归因于以下两个因素：（1）头部、躯干和耳廓的声滤波作用，导致信号频谱发生变化，从而使双耳线索呈现出频率相关的形状；（2）封闭空间内的混响提供的双耳线索。本研究首先通过分析在标准听音室中以不同距离播放的语音的假人头录音，研究了房间混响对双耳水平差（ILD）的时频谱行为的影响。接下来，在相同的听音室中进行的心理声学实验中，研究了 ILD 波动对外显化程度的影响。使用个体双耳脉冲响应来模拟通过耳机传输的远距离声源。使用伽马通滤波器组来改变 ILD，用于分析和合成，其中左右耳信号的包络被修改，从而限制了 ILD 的自然波动。这种操作降低了感知到的外部化程度。这与在不同距离下对短期 ILD 的分析结果一致，表明声源距离的减小也降低了 ILD 的波动。
