The timbre of compound tones consisting of four amplitude modulated waves of different frequency regions

The timbre of compound tones consisting of four amplitude modulated waves is examined by psychoacoustical experiments using a similarity judgement of timbre. The obtained data are analyzed by a multi-dimensional scaling (MDS) method. The MDS solutions are different according to the frequency regions of the AM waves. When the frequency region is low and there is one AM wave within the bandwidth of the auditory filter, envelope correlations between AM waves are a determinant factor of timbre. However, the three dimensional MDS solution suggests that all the envelopes do not affect the timbre in the same manner. The effect of the lowest AM wave is not clear. As the frequency region is higher, the effect of the envelope correlation is less dominant. The effect of the depth of dmplitude modulation of the compound waves then becomes dominant. When there are two AM waves within the bandwidth of the auditory filter, we no longer see the effect of the envelope corre1ation between AM waves. In this case, the correspondence of the shape of the compound enve1opes of two AM waves affect the timbre.