Nelson D A, Fortune T W
Department of Otolaryngology, University of Minnesota, Minneapolis.
J Speech Hear Res. 1991 Apr;34(2):360-73.
Simultaneous-masked psychophysical tuning curves were obtained from normal-hearing listeners using low-level (20-25 dB SPL) probe tones in quiet and high-level (60 dB SPL) probe tones, both in quiet and in the presence of a broad-band background noise. The background noise was introduced to eliminate combination tones or combination bands and other off-frequency listening cues that exist at high levels. Tuning curves were obtained using pure-tone maskers and 100-Hz-wide narrow-band noise maskers for probe tones at 1000 and 4000 Hz. High-level tuning curves for pure-tone maskers demonstrated large discontinuities or "notches" on the low-frequency sides of the tuning curves. Broad-band background noise eliminated those notches, indicating that the notches were due to the detection of off-frequency listening cues at combination-tone frequencies. High-level tuning curves for 100-Hz-wide narrow-band maskers also demonstrated notches on the low-frequency sides. Those notches were eliminated with broad-band background noise, which indicates that combination bands strongly influenced the shapes of high-level tuning curves obtained with narrow-band maskers. The influence of combination bands was dependent upon test frequency. At 1000 Hz, combination bands had very little influence on the shapes of high-level tuning curves. At 4000 Hz, where the masker bandwidth was substantially less than the critical bandwidth, combination bands strongly affected the low-frequency sides of the tuning curves. In 2 subjects tested at a probe frequency of 2000 Hz with 100-Hz-wide masking bands, combination bands also influenced the low-frequency sides of high-level tuning curves. The presence of combination-tone or combination-band cues essentially steepened the low-frequency slopes of tuning curves, resulting in sharper estimates of tuning. Comparisons of tuning curves obtained with pure-tone maskers and narrow-band maskers, in the same listeners, revealed that pure-tone maskers were more effective than narrow-band maskers when the masker frequencies were in the tail region of the tuning curve. The results of these experiments support the notion that tuning in the normal auditory system broadens notably with stimulus level, once off-frequency listening cues such as combination tones or combination bands are eliminated. The low-level simultaneously masked tuning curve demonstrates a sharp bandpass tuning characteristic, whereas the high-level simultaneously masked tuning curve in background noise demonstrates a broad low-pass tuning characteristic.(ABSTRACT TRUNCATED AT 400 WORDS)
通过使用低声级（20 - 25 dB SPL）探测音，在安静环境以及高声级（60 dB SPL）探测音且处于安静环境和存在宽带背景噪声的情况下，从听力正常的受试者获取了同时掩蔽的心理物理调谐曲线。引入背景噪声是为了消除在高声级下存在的组合音或组合带以及其他非频率聆听线索。使用纯音掩蔽器和100 Hz宽的窄带噪声掩蔽器，针对1000 Hz和4000 Hz的探测音获取调谐曲线。纯音掩蔽器的高声级调谐曲线在调谐曲线的低频侧显示出大的不连续或“凹陷”。宽带背景噪声消除了这些凹陷，表明这些凹陷是由于在组合音频率处检测到非频率聆听线索所致。100 Hz宽的窄带掩蔽器的高声级调谐曲线在低频侧也显示出凹陷。这些凹陷被宽带背景噪声消除，这表明组合带强烈影响了用窄带掩蔽器获得的高声级调谐曲线的形状。组合带的影响取决于测试频率。在1000 Hz时，组合带对高声级调谐曲线的形状影响很小。在4000 Hz时，掩蔽器带宽明显小于临界带宽，组合带强烈影响调谐曲线的低频侧。在2名以2000 Hz探测频率和100 Hz宽掩蔽带进行测试的受试者中，组合带也影响了高声级调谐曲线的低频侧。组合音或组合带线索的存在本质上使调谐曲线的低频斜率变陡，从而导致对调谐的估计更精确。在同一受试者中，比较用纯音掩蔽器和窄带掩蔽器获得的调谐曲线发现，当掩蔽器频率在调谐曲线的尾部区域时，纯音掩蔽器比窄带掩蔽器更有效。这些实验结果支持这样一种观点，即一旦消除诸如组合音或组合带等非频率聆听线索，正常听觉系统中的调谐会随着刺激水平显著变宽。低声级同时掩蔽调谐曲线显示出尖锐的带通调谐特性，而在背景噪声中的高声级同时掩蔽调谐曲线显示出宽泛的低通调谐特性。（摘要截断于400字）
