Patent ID: 7754958

Claim:
A sound analysis apparatus for analyzing an input audio signal based on a weighted mixture of a plurality of tone models which represent harmonic structures of sound sources and which correspond to probability density functions of various fundamental frequencies, the apparatus comprising: a probability density estimation part that sequentially updates and optimizes respective weights of the plurality of the tone models, so that a mixed distribution of frequencies obtained by the weighted mixture of the plurality of the tone models corresponding respectively to the various fundamental frequencies approximates an actual distribution of frequency components of the input audio signal, and that estimates the optimized weights of the tone models to be a fundamental frequency probability density function of the various fundamental frequencies corresponding to the sound sources; and a fundamental frequency determination part that determines an actual fundamental frequency of the input audio signal based on the fundamental frequency probability density function estimated by the probability density estimation part, wherein the probability density estimation part comprises: a storage part that stores sound source structure data defining a constraint on one or more of sounds that can be simultaneously generated by a sound source of the input audio signal, a form estimation part that selects fundamental frequencies of one or more of sounds likely to be contained in the input audio signal with peaked weights from the various fundamental frequencies during the sequential updating and optimizing of the weights of the tone models corresponding to the various fundamental frequencies, so that the sounds of the selected fundamental frequencies satisfy the sound source structure data, and that creates form data specifying the selected fundamental frequencies, and a previous distribution imparting part that imparts a previous distribution to the weights of the tone models corresponding to the various fundamental frequencies so as to emphasize weights corresponding to the fundamental frequencies specified by the form data created by the form estimation part.