Dynamic perception process of the three dimensional spatial hearing

在本研究中，一个新的空间听觉控制系统，其中的头部相关的传递函数（HRTF）切换通过感知听者的头部运动的第一次开发。该系统由多个50 MFLOPS的DSP芯片组成，实现了相对于头部运动切换HRTF的仅13 ms的极短延迟时间。通过使用上述系统，检测阈值和HRTF切换中的延迟时间的差异阈值（DL）的心理测量成为可能。作为结果，它是第一次表明，检测阈值约为50毫秒和DL突然增加的延迟时间长于100毫秒，这些发现是新的，有趣的和重要的。在此基础上，通过心理声学实验研究了人在两种头部运动情况下的声音定位能力。在一种情况下，听众只被允许移动他们的头部，而在另一种情况下，听众被要求主动移动他们的头部，以尽可能精确地定位声像。分别用低通噪声、高通噪声和持续时间为100 ms ~ 3 s的宽带噪声作为声刺激。因此，主动头部运动的效果对于降低低通噪声的定位误差特别有效。此外，用运动传感器记录头部运动的轨迹。结果表明，一些有趣的趋势，如明确的垂直运动过程中的本地化的声像在水平面上。

In the present study, a new spatial hearing control system, in which the head-related transfer functions (HRTF) are switched over by sensing the motion of listener's head was first developed. This system is consisted of multiple DSP chips of 50 MFLOPS in speed and realizes very short delay time of only 13 ms in switching HRTFs against the head motion. By using the above mentioned system, the psychometric measurement of the detection threshold and the difference limen (DL) of the delay time in the switching of HRTF become possible. As results, it was first showed that the detection threshold is around 50 ms and the DL suddenly increase for delay time longer than 100 ms; these finding are new, interesting and important ones. Then, a psychoacoustical experiments were conducted to examine the human ability of sound localization under two conditions of head moving. In one condition, listeners were just allowed to move their heads while in the other condition, listeners were requested to move their heads actively to locate the sound image as precisely as possible. Low-passed noise, High-passed noise as well as wide-band noise with duration from 100 ms to 3 s were used as sound stimuli. As a result, the effect of active head movement was particularly effective to reduce localization errors for the low-passed noise. Moreover, the loci of the head movements were recorded with a motion sensor. The results showed some interesting tendencies such as clear vertical motions during the localization of a sound image on the horizontal plane.