Buus S, Florentine M
Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts 02115.
J Acoust Soc Am. 1991 Sep;90(3):1371-80. doi: 10.1121/1.401928.
To determine the form of psychometric functions for 2I,2AFC level discrimination (commonly called intensity discrimination), ten increment levels were presented in random order within blocks of 100 trials. Stimuli were chosen to encompass a wide range of conditions and difference limens: eight 10-ms tones had frequencies of 0.25, 1, 8, or 14 kHz and levels of 30, 60, or 90 dB SPL; two 500-ms stimuli also were tested: a 1-kHz tone at 90 dB SPL and broadband noise at 63 dB SPL. For each condition, at least 20 blocks were presented in mixed order. Results for five normal listeners show that the sensitivity, d', is nearly proportional to delta L (= 20 log [(p + delta p)/p], where p is sound pressure) over the entire range of difference limens. When d' is plotted against Weber fractions for sound pressure, delta p/p, or intensity, delta I/I, exponents of the best-fitting power functions decrease with increasing difference limens and are less than unity for large difference limens. The approximately proportional relation between d' and delta L agrees with modern multichannel models of level discrimination and with psychometric functions derived for single auditory-nerve fibers. The results also support the notion that the difference limen, expressed as delta LDL and plotted on a logarithmic scale, is an appropriate representation of performance in level-discrimination experiments.
为了确定用于2I、2AFC水平辨别（通常称为强度辨别）的心理测量函数形式，在100次试验的组内以随机顺序呈现了10个增量水平。选择的刺激涵盖了广泛的条件和差别阈限：8个10毫秒的纯音，频率分别为0.25、1、8或14千赫，声压级分别为30、60或90分贝声压级；还测试了2个500毫秒的刺激：90分贝声压级的1千赫纯音和63分贝声压级的宽带噪声。对于每种条件，以混合顺序呈现至少20组。5名正常听力者的结果表明，在整个差别阈限范围内，灵敏度d'几乎与ΔL（=20log[(p + Δp)/p]，其中p是声压）成正比。当将d'与声压、Δp/p或强度、ΔI/I的韦伯分数作图时，最佳拟合幂函数的指数随差别阈限的增加而减小，对于较大的差别阈限小于1。d'与ΔL之间的近似比例关系与现代水平辨别多通道模型以及为单根听神经纤维推导的心理测量函数一致。结果还支持这样一种观点，即以ΔLDL表示并以对数标度作图的差别阈限是水平辨别实验中表现的合适表示。
