Nelson D A, Freyman R L
J Acoust Soc Am. 1987 Mar;81(3):709-20. doi: 10.1121/1.395131.
Temporal masking curves were obtained from 12 normal-hearing and 16 hearing-impaired listeners using 200-ms, 1000-Hz pure-tone maskers and 20-ms, 1000-Hz fixed-level probe tones. For the delay times used here (greater than 40 ms), temporal masking curves obtained from both groups can be well described by an exponential function with a single level-independent time constant for each listener. Normal-hearing listeners demonstrated time constants that ranged between 37 and 67 ms, with a mean of 50 ms. Most hearing-impaired listeners, with significant hearing loss at the probe frequency, demonstrated longer time constants (range 58-114 ms) than those obtained from normal-hearing listeners. Time constants were found to grow exponentially with hearing loss according to the function tau = 52e0.011(HL), when the slope of the growth of masking is unity. The longest individual time constant was larger than normal by a factor of 2.3 for a hearing loss of 52 dB. The steep slopes of the growth of masking functions typically observed at long delay times in hearing-impaired listeners' data appear to be a direct result of longer time constants. When iterative fitting procedures included a slope parameter, the slopes of the growth of masking from normal-hearing listeners varied around unity, while those from hearing-impaired listeners tended to be less (flatter) than normal. Predictions from the results of these fixed-probe-level experiments are consistent with the results of previous fixed-masker-level experiments, and they indicate that deficiencies in the ability to detect sequential stimuli should be considerable in hearing-impaired listeners, partially because of extended time constants, but mostly because forward masking involves a recovery process that depends upon the sensory response evoked by the masking stimulus. Large sensitivity losses reduce the sensory response to high SPL maskers so that the recovery process is slower, much like the recovery process for low-level stimuli in normal-hearing listeners.
使用200毫秒、1000赫兹的纯音掩蔽音和20毫秒、1000赫兹的固定电平探测音，从12名听力正常的听众和16名听力受损的听众那里获得了时间掩蔽曲线。对于这里使用的延迟时间（大于40毫秒），两组获得的时间掩蔽曲线都可以用一个指数函数很好地描述，每个听众有一个与电平无关的单一时间常数。听力正常的听众表现出的时间常数在37至67毫秒之间，平均为50毫秒。大多数在探测频率处有明显听力损失的听力受损听众表现出比听力正常的听众更长的时间常数（范围为58 - 114毫秒）。当掩蔽增长的斜率为1时，发现时间常数根据函数tau = 52e0.011(HL)随听力损失呈指数增长。对于52分贝的听力损失，最长的个体时间常数比正常情况大2.3倍。在听力受损听众的数据中，通常在长延迟时间观察到的掩蔽函数增长的陡峭斜率似乎是时间常数较长的直接结果。当迭代拟合程序包括一个斜率参数时，听力正常的听众的掩蔽增长斜率在1左右变化，而听力受损的听众的斜率往往比正常情况小（更平缓）。这些固定探测电平实验的结果预测与先前固定掩蔽电平实验的结果一致，并且它们表明听力受损的听众在检测序列刺激的能力方面存在相当大的缺陷，部分原因是时间常数延长，但主要是因为前向掩蔽涉及一个依赖于掩蔽刺激诱发的感觉反应的恢复过程。大的灵敏度损失会降低对高声压级掩蔽音的感觉反应，从而使恢复过程变慢，这很像听力正常的听众对低电平刺激的恢复过程。
