Bacon S P, Lee J, Peterson D N, Rainey D
Department of Speech and Hearing Science, Arizona State University, Tempe 85287-1908, USA.
J Acoust Soc Am. 1997 Mar;101(3):1600-10. doi: 10.1121/1.418175.
The threshold for a sinusoidal signal masked by a band of noise is often times lower when the masking noise is modulated than when it is unmodulated. The difference in masked thresholds is referred to as the modulated-unmodulated difference, or MUD. These present experiments examined the effects of masker bandwidth, masker rate, and masker level on the MUD at several different signal frequencies. The MUD generally increased with increasing masker bandwidth; for masker bandwidths wider than a critical band (or an equivalent rectangular bandwidth-ERB), the results may be influenced by across-channel processes underlying comodulation masking release. The MUD for an ERB masker (MUDERB) was influenced less by masker rate than was the MUD for a broadband (BB) masker (MUDBB). The MUDERB and especially the MUDBB increased significantly with increasing masker level when the modulated masker was modulated at a depth (m) of 1.0, but not when it was modulated at a depth of 0.75. These results have significant implications for extending the MUD paradigm to hearing-impaired subjects. Finally, the MUDERB and the MUDBB increased with increasing signal frequency. This effect for the ERB masker is largely (if not completely) due to the wider absolute bandwidths at higher frequencies. The effect with the BB masker may be influenced by differences in the magnitude of suppression across frequency.
当掩蔽噪声被调制时，被噪声带掩蔽的正弦信号的阈值通常比未调制时要低。掩蔽阈值的差异被称为调制 - 未调制差异，即MUD。这些实验研究了在几个不同信号频率下，掩蔽器带宽、掩蔽器速率和掩蔽器电平对MUD的影响。MUD通常随着掩蔽器带宽的增加而增大；对于比临界带宽（或等效矩形带宽 - ERB）更宽的掩蔽器带宽，结果可能会受到共调制掩蔽释放背后的跨通道过程的影响。ERB掩蔽器的MUD（MUDERB）比宽带（BB）掩蔽器的MUD（MUDBB）受掩蔽器速率的影响更小。当调制掩蔽器以1.0的深度（m）调制时，MUDERB尤其是MUDBB会随着掩蔽器电平的增加而显著增大，但当以0.75的深度调制时则不会。这些结果对于将MUD范式扩展到听力受损受试者具有重要意义。最后，MUDERB和MUDBB随着信号频率的增加而增大。ERB掩蔽器的这种效应在很大程度上（如果不是完全）是由于较高频率下更宽的绝对带宽。BB掩蔽器的效应可能会受到跨频率抑制幅度差异的影响。
