PURPOSE: To enable analysis of frequency portions relatively with the same capacity regardless of the level thereof, low and high, and with a limited number of data by selecting frequency to take in data from in a manner of geometric series.

CONSTITUTION: The pass band width of a variable frequency band pass filter 10 with which a pass band is swept and controlled is proportional to the center frequency fo so that Q is unchanged regardless of variation in the center frequency fo. Gains Gn and Gn+1, namely, pass bands of a filter 10 are arranged very closely with respect to center frequencies fn and fn+1 as specified by a frequency setter 11 for outputting a control signal setting the pass bands of the filter 10 and a gate timing signal. The analysis data is as illustrated [frequency (f) on the axis of abscissa and component sound pressure P on the axis of ordinate]. Compared with the selection of arithmetic progression, this can reduce the number of data and also enables analysis relatively with the same capacity even at a low rotation to reduce the processing time.