The effect of amplitude envelopes of each amplitude modulated wave on the timbre of compound tones consisting of three amplitude modulated waves

The timbre of compound tones consisting of three amplitude modulated waves is examined by psychoacoustical experiments using a similarity judgement. The obtained data are analyzed by a multi-dimensional scaling (MDS) method. The MDS solutions are interpreted by the regression equations as a function of the envelope correlation coefficients between the AM waves. In particular, the envelope correlations between adjacent AM waves are the determinant factor. When the modulation rate is slow enough, the fine structure of amplitude envelopes of each AM wave affects the timbre. However, the modulation rate is faster than the auditory temporal resolving power, the fine structure has no effect and the timbre is determined by only the envelope correlations. The auditory system has a function to detect the amplitude envelope correlation between the output signals of the different auditory filters. The present study shows how this function contributes to timbre perception.