PURPOSE: To reduce the entire circuit scale by reproducing time series data of a 2nd sampling frequency different from a 1st sampling frequency when inputted compression data are subjected to frequency/time conversion.

CONSTITUTION: Time series data with a sampling frequency different from an original sampling frequency are obtained by a frequency/time conversion (inverting mapping) section 1. An input X(k) is a frequency sampling value, which is subjected to inverse mapping arithmetic operation by a multiplier adder 1a and a coefficient generator 1b. The frequency component X(k) is refreshed in the unit of blocks. The generator 1b generates a frequency/time conversion coefficient C(k, t) in the size of one block up to (2n-) sequentially from t=0 at the sampling period with respect to each frequency component. The result of multiplication between each frequency component and the coefficient is added and an output x(t) is obtained, and samples of frequency components are arranged on a frequency axis. Since the sample is converted for each block of a prescribed time length, the position on the frequency axis is limited a certain interval.