A Study on Mechanism of Processing, Perception and Cognition of Auditory Signal.

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In this project, we measure frequency difference limen (D. L.) when jitter (random fluctuation of frequency components) added to a pure tone and complex tones which have three components with various durations of stimuli. The results show that increment of D.L. induced by jitter for pure tone was rarer than that for complex tones, and in short term region non-jittered stimuli with higher frequency components had smaller D. L. than one with lower frequency components. These results indicate that D. L. could be related to the pitch strength which derived from autocorrelation model. Furthermore the results obtained pitch match experiments using 3 and 6 components complex tones, especially ones with small pitch shift, support autocorrelation model. However, the results with larger pitch shift can not be explained well using this model.The quantization noise (harmonic distortion) and the broad band noise due to dither are evaluated. The results are as follows ; using exponentially decayed signal as test tone, generally the effectiveness of dither are confirmed as the increase of detection level. And using complex tones which have three or five components as test tone, the effects of dither are changed due to the fundamental frequency of test tones and the dither is not always effective in this case. The detection model of distortion based on the masking effect can explain this phenomenon.From the study of attention of human auditory information processing, the hit rate in detection task increases and the rate of false alarm decreases when temporal information of tone occurrence is give.