Sound signal analyzing device

Abstract

An average is calculated of every predetermined number of sample amplitude values of a sound signal from an external sound source, and the respective averages are output as a time-series of average level information. On the basis of the average level information, each available section of the sound signal is detected where there appears to be a musical sound. On the basis of degrees of inclination in the average level information within the available section, stable sections are detected for detection of same-waveform sections. On the basis of the signals within the stable sections, a steady section is detected which corresponds to a note. A time-varying band-pass filtering operation is then performed on the sound signal, and detection is made of a plurality of periodic reference points of the sound signal. Subsequently, degrees of similarity in waveform are determined between every adjacent signal sections of the sound signal corresponding to the periodic reference points and those of the signal sections having a high similarity are linked together so as to detect same-waveform sections. These same-waveform sections are subdivided in consideration of level stability or the like, so as to detect a steady section representing a note. Thus, even when an input sound from a microphone or the like fluctuates slightly in pitch or level, each steady section of the sound other than the fluctuating section can be effectively analyzed.