A frequency setting unit (120) acquires information representing required sound quality for sound output from parametric speakers (140). The frequency setting unit (120) performs determination about whether or not to make the frequency of a modulation signal mutually different among a plurality of parametric speakers (140) based on information representing the acquired sound quality. The frequency setting unit (120) sets the frequency of the modulation signal in each of a plurality of parametric speakers (140) based on the determination result. The modulation unit (130) generates modulation signals having the frequencies set by the frequency setting unit (120). The modulation signals are input to the plurality of parametric speakers (140).
