Nix Johannes, Hohmann Volker
Medizinische Physik, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Germany.
J Acoust Soc Am. 2006 Jan;119(1):463-79. doi: 10.1121/1.2139619.
The role of temporal fluctuations and systematic variations of interaural parameters in localization of sound sources in spatially distributed, nonstationary noise conditions was investigated. For this, Bayesian estimation was applied to interaural parameters calculated with physiologically plausible time and frequency resolution. Probability density functions (PDFs) of the interaural level differences (ILDs) and phase differences (IPDs) were estimated by measuring histograms for a directional sound source perturbed by several types of interfering noise at signal-to-noise ratios (SNRs) between -5 and +30 dB. A moment analysis of the PDFs reveals that the expected values shift and the standard deviations increase considerably with decreasing SNR, and that the PDFs have non-Gaussian shape at medium SNRs. A d' analysis of the PDFs indicates that elevation discrimination is possible even at low SNRs in the median plane by integrating information across frequency. Absolute sound localization was simulated by a Bayesian maximum a posteriori (MAP) procedure. The simulation is based on frequency integration of broadly tuned "detectors." Confusion patterns of real and estimated sound source directions are similar to those of human listeners. The results indicate that robust processing strategies are needed to exploit interaural parameters successfully in noise conditions due to their strong temporal fluctuations.
研究了时间波动和双耳参数的系统变化在空间分布的非平稳噪声条件下声源定位中的作用。为此，将贝叶斯估计应用于以生理上合理的时间和频率分辨率计算出的双耳参数。通过测量在-5至+30 dB的信噪比下受几种干扰噪声干扰的定向声源的直方图，估计了双耳声级差（ILD）和相位差（IPD）的概率密度函数（PDF）。对PDF的矩分析表明，随着信噪比降低，期望值会发生偏移，标准差会显著增加，并且在中等信噪比下PDF具有非高斯形状。对PDF的d'分析表明，通过跨频率整合信息，即使在低信噪比下，在中平面也可以进行仰角辨别。通过贝叶斯最大后验（MAP）程序模拟了绝对声源定位。该模拟基于广泛调谐的“探测器”的频率积分。真实声源方向和估计声源方向的混淆模式与人类听众的相似。结果表明，由于双耳参数存在强烈的时间波动，因此在噪声条件下需要强大的处理策略才能成功利用双耳参数。
