Cochlear Implants and Psychophysics Lab, Department of Hearing & Speech Sciences, University of Maryland, College Park, MD 20742, USA.
Hear Res. 2011 Dec;282(1-2):225-35. doi: 10.1016/j.heares.2011.07.005. Epub 2011 Jul 28.
Three experiments investigated listeners' ability to detect a narrow band of noise, centered on one partial of a random-phase complex tone, as a function of inharmonicity. Inharmonicity was generated by randomly mistuning the partial frequencies from a 100-Hz fundamental frequency (F0). In experiment 1, masked detection thresholds were lower when the masker was harmonic than when it was inharmonic for target bands in the range 0.5-2.5 kHz. The presence of this masking level difference due to harmonicity (HMLD) in regions of resolved partials and the reduction of the HMLD with increasing center frequency did not support the idea that HMLD was primarily caused by the envelope modulations produced by the beating of unresolved partials within an auditory filter. In experiment 2, masker mistunings ranging beyond 12% of the F0 disrupted the HMLD while smaller mistunings gave thresholds similar to a harmonic masker. In experiment 3, all partials contributed to some extent to the HMLD, but the harmonicity of partials neighboring the target had a greater influence than distant partials. The observed HMLDs can best be accounted for by a mechanism of harmonic cancellation.
三项实验研究了听者在听随机相位复合音时检测中心频率位于一个分音上的窄带噪声的能力，该分音的频率是由基频（F0）100Hz 的随机失谐产生的。在实验 1 中，当掩蔽噪声是谐波时，其检测阈值比非谐波时更低，而目标带宽在 0.5-2.5kHz 范围内。在可分辨分音区域存在由于谐波引起的掩蔽水平差（HMLD），以及随着中心频率的增加 HMLD 减少的现象，并不支持 HMLD 主要是由听觉滤波器内未分辨分音的拍频产生的包络调制引起的观点。在实验 2 中，掩蔽噪声的失谐超过 F0 的 12% 会破坏 HMLD，而较小的失谐则会使阈值与谐波掩蔽相似。在实验 3 中，所有分音都在一定程度上对 HMLD 有贡献，但临近目标的分音的谐波性比远距离分音的影响更大。观察到的 HMLD 可以通过谐波抵消机制得到最好的解释。
