Zahorik Pavel
Waisman Center, University of Wisconsin-Madison, 53705, USA.
J Acoust Soc Am. 2002 Nov;112(5 Pt 1):2110-7. doi: 10.1121/1.1506692.
Although the ratio of direct-to-reverberant sound energy is known to be an important acoustic cue to sound source distance, human sensitivity to changes in this cue is largely unknown. Here, direct-to-reverberant energy discrimination thresholds were measured for six listeners using virtual sound source techniques that allow for convenient and precise control of this stimulus parameter. Four different types of source stimuli were tested: a 50 ms noise burst with abrupt onset/offset, a 300 ms duration noise burst with gradual onset/offset, a speech syllable, and an impulse. Over a range of direct-to-reverberant ratios from 0 to 20 dB, an adaptive 2AFC procedure (3-down, 1-up) was used to measure discrimination thresholds. For all stimuli, these thresholds ranged from 5 to 6 dB. A post hoc fitting procedure confirmed that slopes of the psychometric functions were homogeneous across stimulus conditions and listeners. These threshold results suggest that direct-to-reverberant energy ratio by itself provides only a course coding of sound source distance, because threshold values correspond to greater than 2-fold changes in physical distance for the acoustic environment under examination.
尽管直达声与混响声的声能比是声源距离的重要声学线索，但人类对该线索变化的敏感度在很大程度上仍不清楚。在此，使用虚拟声源技术对六位听众的直达声与混响声能量辨别阈值进行了测量，该技术能够方便且精确地控制这一刺激参数。测试了四种不同类型的声源刺激：起始/结束突然的50毫秒噪声脉冲、起始/结束渐变的300毫秒时长噪声脉冲、一个语音音节以及一个脉冲。在0至20分贝的直达声与混响声比值范围内，采用自适应2AFC程序（3次下降，1次上升）来测量辨别阈值。对于所有刺激，这些阈值范围为5至6分贝。事后拟合程序证实，心理测量函数的斜率在不同刺激条件和听众之间是均匀的。这些阈值结果表明，直达声与混响声能量比本身仅提供了声源距离的粗略编码，因为在被研究的声学环境中，阈值对应于物理距离上超过2倍的变化。
