Buss Emily, Hall Joseph W
Department of Otolaryngology/Head and Neck Surgery, University of North Carolina, School of Medicine, Chapel Hill, North Carolina 27599, USA.
J Acoust Soc Am. 2010 Jun;127(6):3666-77. doi: 10.1121/1.3377053.
The present studies examined the binaural masking level difference (MLD) for off-frequency masking. It has been shown previously that the MLD decreases steeply with increasing spectral separation between a pure tone signal and a 10-Hz wide band of masking noise. Data collected here show that this reduction in the off-frequency MLD as a function of signal/masker separation is comparable at 250 and 2500 Hz, indicating that neither interaural phase cues nor frequency resolution are critical to this finding. The MLD decreases more gradually with spectral separation when the masker is a 250-Hz-wide band of noise, a result that implicates the rate of inherent amplitude modulation of the masker. Thresholds were also measured for a brief signal presented coincident with a local masker modulation minimum or maximum. Sensitivity was better in the minima for all NoSpi and off-frequency NoSo conditions, with little or no effect of signal position for on-frequency NoSo conditions. Taken together, the present results indicate that the steep reduction in the off-frequency MLD for a narrowband noise masker is due at least in part to envelope cues in the NoSo conditions. There was no evidence of a reduction in binaural cue quality for off-frequency masking.
本研究考察了偏离频率掩蔽的双耳掩蔽级差（MLD）。先前的研究表明，随着纯音信号与10赫兹宽带掩蔽噪声之间频谱分离度的增加，MLD会急剧下降。此处收集的数据表明，在250赫兹和2500赫兹时，作为信号/掩蔽器分离度函数的偏离频率MLD的这种降低是相当的，这表明双耳相位线索和频率分辨率对这一发现都不是关键因素。当掩蔽器是250赫兹宽带噪声时，MLD随频谱分离度下降得更为平缓，这一结果暗示了掩蔽器固有幅度调制的速率。还测量了与局部掩蔽器调制最小值或最大值同时出现的短暂信号的阈值。在所有无频谱干扰（NoSpi）和偏离频率无频谱干扰（off-frequency NoSo）条件下，最小值处的灵敏度更高，而在频率匹配无频谱干扰（on-frequency NoSo）条件下，信号位置的影响很小或没有影响。综合来看，目前的结果表明，窄带噪声掩蔽器的偏离频率MLD急剧下降至少部分归因于NoSo条件下的包络线索。没有证据表明偏离频率掩蔽的双耳线索质量会降低。
