Kollmeier B, Holube I
Drittes Physikalisches Institut, Universität Göttingen, Germany.
J Acoust Soc Am. 1992 Oct;92(4 Pt 1):1889-901. doi: 10.1121/1.405264.
The shape and the effective bandwidth of the auditory filter at 500 Hz was examined for binaural and monaural tone-in-noise detection experiments in four normal listeners. In the binaural condition, a broadband noise with an interaural phase difference of 0 below and an interaural phase difference of pi above a certain "edge frequency" was employed to mask a 500-Hz probe tone with an interaural phase pi (denoted as No pi S pi). The threshold of the probe tone as a function of the edge frequency in this configuration and in a configuration with an inverted interaural phase of the masker (denoted as N pi oS pi) was fitted by assuming different filter shapes and optimizing their respective parameters. In an analogous monaural experiment, the spectral power density of the masker was 15 dB lower below the "edge frequency" or 15 dB lower above this frequency, respectively. Several filter characteristics with two free parameters describe the data almost equally well. Their equivalent rectangular bandwidths (ERB) show considerably more variations between filter shapes than the 10-dB bandwidth and the 90% bandwidth values (i.e., the bandwidths encompassing 90% of the integrated area above and below the center frequency). This indicates that either of these two bandwidth parameters is more appropriate for comparing auditory filter bandwidths than the ERB. For the rounded exponential filter, the 90% bandwidth averages to 147 Hz in the binaural and to 125 Hz in the monaural condition. These values are up to 12% higher if off-frequency detection is accounted for. Our general finding of auditory filter bandwidths in the binaural conditions exceeding the monaural bandwidths by approximately 20% may be caused by two factors: First, off-frequency detection may be performed in monaural, but not in binaural detections tasks and second, the random interaural mismatch in binaural noise reduction processes fluctuates slowly and thus modulates and spectrally smears the output signal of the binaural noise reduction process.
在四名正常听力受试者中，针对双耳和单耳的纯音加噪声检测实验，研究了500赫兹处听觉滤波器的形状和有效带宽。在双耳条件下，采用一种宽带噪声，在某个“边缘频率”以下双耳相位差为0，在该频率以上双耳相位差为π，以掩蔽一个双耳相位为π的500赫兹探测音（记为No pi S pi）。通过假设不同的滤波器形状并优化其各自参数，拟合了该配置下以及掩蔽器双耳相位反转配置（记为N pi oS pi）中探测音阈值随边缘频率的变化。在类似的单耳实验中，掩蔽器的频谱功率密度在“边缘频率”以下分别低15分贝，或在该频率以上低15分贝。具有两个自由参数的几种滤波器特性对数据的描述几乎同样好。它们的等效矩形带宽（ERB）在不同滤波器形状之间的变化比10分贝带宽和90%带宽值（即包含中心频率上下90%积分面积的带宽）大得多。这表明这两个带宽参数中的任何一个都比ERB更适合用于比较听觉滤波器带宽。对于圆形指数滤波器，在双耳条件下90%带宽平均为147赫兹，在单耳条件下为125赫兹。如果考虑离频检测，这些值会高出多达12%．我们发现双耳条件下听觉滤波器带宽比单耳带宽大约宽20%，这可能由两个因素导致：第一，单耳检测任务中可能会进行离频检测，而双耳检测任务中不会；第二，双耳降噪过程中的随机双耳失配波动缓慢，从而调制并在频谱上 smear 双耳降噪过程的输出信号。
