Hartmann W M, Pumplin J
Physics Department, Michigan State University, East Lansing 48824-1116.
J Acoust Soc Am. 1988 Jun;83(6):2277-89. doi: 10.1121/1.396358.
This article is concerned with fluctuations in noise power and with the role that such fluctuations play in the masking of sine signals by noise. Several measures of noise fluctuations are discussed: the fourth moment of the waveform, the fourth moment of the envelope, and the crest factor. Relationships among these quantities are found for cases of equal-amplitude random-phase noise and Rayleigh-distributed-amplitude noise. Of particular interest is a special non-Gaussian noise called low-noise noise in which the fluctuations are small by any of our measures. The results of frozen-noise masking experiments are reported, where the noise waveform was fixed for all stimulus presentations. In separate experiments, equal-amplitude random-phase Gaussian noise, with typical fluctuations, and low-noise noise, with almost no fluctuations were used. The data show that for a noise bandwidth less than the critical bandwidth, the masked threshold is about 5 dB lower for low-noise noise than for Gaussian noise. When the noise bandwidth is larger than the critical bandwidth, the masked threshold is the same for both kinds of noise. It is concluded that noise power fluctuations increase masked threshold by about 5 dB and that filtering by the auditory system reintroduces fluctuations into broadband low-noise noise.
本文关注噪声功率的波动以及此类波动在噪声对正弦信号掩蔽中所起的作用。讨论了几种噪声波动的度量：波形的四阶矩、包络的四阶矩以及波峰因数。针对等幅随机相位噪声和瑞利分布幅度噪声的情况，找出了这些量之间的关系。特别令人感兴趣的是一种特殊的非高斯噪声，称为低噪声噪声，用我们的任何一种度量方法衡量，其波动都很小。报告了冻结噪声掩蔽实验的结果，在所有刺激呈现过程中噪声波形都是固定的。在单独的实验中，使用了具有典型波动的等幅随机相位高斯噪声以及几乎没有波动的低噪声噪声。数据表明，对于小于临界带宽的噪声带宽，低噪声噪声的掩蔽阈值比高斯噪声低约5dB。当噪声带宽大于临界带宽时，两种噪声的掩蔽阈值相同。得出的结论是，噪声功率波动使掩蔽阈值提高约5dB，并且听觉系统的滤波作用会将波动重新引入宽带低噪声噪声中。
