PURPOSE: To generate a synthetic sound which has a sharp peak in the center of a formant shape by adding a DC component to a noise waveform which has specific spectrum characteristics and multiplying the result by the period waveform of specific frequency.

CONSTITUTION: A white noise from a white noise generator 1 becomes a white noise with a right-down waveform to which the DC component is added by an adder which performs offset processing and a digital filter 3 which performs spectrum processing for giving low-pass characteristics. A multiplier 5 multiplies this noise by the waveform such as a sine wave of the period waveform corresponding to the specified center frequency of the formant outputted by a period waveform generating circuit 4. Consequently, the noise having the sharp peak in the center of the formant shape is generated by frequency convolution and the center frequency of the formant shape can be varied optionally and easily.