Bernstein L R, Trahiotis C
Center for Neurological Sciences, University of Connecticut Health Center, Farmington 06030.
J Acoust Soc Am. 1994 Feb;95(2):920-30. doi: 10.1121/1.408401.
Listeners' detection thresholds were measured for a 125-ms, 1-kHz tonal signal masked by a similarly gated 50-Hz-wide band of noise. A two-interval, adaptive, forced-choice procedure either with or without temporally surrounding cuing intervals containing 50-Hz-wide bands of noise was employed. When the cues were present, their center frequency was either 1 kHz (on-frequency) or 900 or 700 Hz (off-frequency). In the conditions of principal interest, the envelopes and phase modulations of the bands of noise were "frozen" across the four intervals that defined a trial, but were chosen randomly across trials. Thresholds were lowest with cues centered at 1 kHz and increased substantially when the center frequency of the cues was changed to 900 or 700 Hz. With cues centered at 700 Hz, performance was equivalent to that obtained without cues and with the masking noise "frozen" across the two intervals that defined a trial. A similar pattern of results was obtained with high-frequency stimuli, where sensitivity to fine-structure information is greatly reduced. Roving the level of the stimuli over a 40-dB range generally reduced sensitivity but did not greatly affect the overall pattern of the data. Thresholds obtained in the two-interval task with masking waveforms chosen randomly were compared with thresholds obtained when the masking waveform was "frozen" within, but not across trials. Differences in threshold appeared to be accounted for by the listeners' use of changes in the mean slope of the envelope of the noise produced by adding the tonal signal.
针对由类似门控的50赫兹宽带噪声掩蔽的125毫秒、1千赫兹音调信号，测量了听众的检测阈值。采用了两间隔、自适应、强制选择程序，该程序带有或不带有包含50赫兹宽带噪声的时间上周围的提示间隔。当存在提示时，其中心频率为1千赫兹（同频）或900或700赫兹（异频）。在主要感兴趣的条件下，噪声带的包络和相位调制在定义一次试验的四个间隔内是“冻结”的，但在不同试验中是随机选择的。当提示的中心频率为1千赫兹时阈值最低，而当提示的中心频率变为900或700赫兹时阈值大幅增加。当提示的中心频率为700赫兹时，表现与没有提示且掩蔽噪声在定义一次试验的两个间隔内“冻结”时获得的表现相当。对于高频刺激也获得了类似的结果模式，在高频刺激中对精细结构信息的敏感度大大降低。在40分贝范围内改变刺激水平通常会降低敏感度，但对数据的总体模式影响不大。将在随机选择掩蔽波形的两间隔任务中获得的阈值与当掩蔽波形在试验内（而非跨试验）“冻结”时获得的阈值进行了比较。阈值差异似乎是由听众利用添加音调信号所产生的噪声包络平均斜率的变化来解释的。
