A sound synthesis system to help cognition experiments of higher animals Prof.

本计画旨在建立一个电脑辅助的声音合成系统，并将其应用于听觉生理与行为实验。微型计算机的最新进展使我们能够处理高达50 kHz的声音信号。由于该项目的研究人员关注的是猴子的听觉神经生理学或鸟类的发声行为，因此，为了获得神经元或动物的准确反应，需要适当的刺激声。购买或自制软件进行声音的记录、FFT频谱的提取、滤波、成分提取、部分声音的截取和刺激声音的再现，并于1989年应用于听觉生理学和行为学实验的刺激声音合成。对20种日本猴叫声进行了分析和修改。其中，“咕咕”的声音被分成共振峰成分，并使猴子听到这些声音作为刺激。人为地改变了“平滑早高”和“平滑晚高”的频率向上或向下漂移的速率。这些刺激被用来获得听觉皮层神经元的反应。Leach的风暴海燕的呼叫中存在性别二型性。这种差异主要是由于呼叫的频率不同。该系统可以产生模拟的声音与频率成分之间的原始男性和女性的呼吁。这种鸟的叫声有其特有的节奏。节奏也被计算机人为地修改了。这些样本声音是为行为实验准备的。另外还设计了一个实验来测试鸟如何区分同属不同种的鸟的叫声，实验结果表明，微机辅助系统为这些实验提供了非常有效的工具。

This project aimed to build a microcomputer aided sound synthesis system and to apply it to auditory physiology and behavioral experiments. Recent progress of microcomputers enabled us to treat the sound signals up to 50 kHz. Since the researchers under this project were concerned with auditory neurophysiology of monkey or vocal behavior of birds, appropriate stimulus sounds were necessary for experiments to get the exact response from neurons or animals.In 1988, the microcomputer was combined with A/D, D/A converters. The softwares were bought or made to record the sound, to get FFT spectrum, to filter the sounds, to extract the components, to cut out the part of the sounds and to reproduce the stimulus sounds.In 1989, the system was applied to synthesize stimulus sounds for auditory physiology and behavioral experiments. About 20 calls of Japanese monkey were analyzed and modified. Out of them, "coo" sounds were divided to the formant component and made a monkey hear the sounds as stimuli. The rate of frequency drift, upward or downward, of "'smooth early high" and "smooth late high" was artificially changed. These stimuli were used to get the responses from the neurons of auditory cortex.There is a sexual dimorphism in the calls of Leach's Storm-petrel. The difference is mainly due to the frequency of the note of the calls. The system could produce mimic calls with frequency components in-between original male and female calls. The calls of this bird have characteristic rhythms. The rhythm was also artificially modified by the computer. These sample sounds were prepared for behavioral experiment. The other experiments were designed to test how the bird can differentiate the calls of the bird belonging to different species of the same genus.The results showed that the microcomputer aided system offers very effective tools for these experiments.