1. A sound processing device comprising: a separation unit configured to separate at least a music signal and a speech signal from a recorded audio signal; a noise suppression unit configured to perform a noise suppression process of suppressing noise from at least one of the music signal and the speech signal separated by the separation unit; a music feature value estimation unit configured to estimate a feature value of the music signal from the music signal; a speech recognition unit configured to recognize speech from the speech signal; a noise-processing confidence calculation unit configured to calculate a noise-processing confidence value which is a confidence value relevant to the noise suppression process; a music feature value estimation confidence calculation unit configured to calculate a music feature value estimation confidence value which is a confidence value relevant to the process of estimating the feature value of the music signal; a speech recognition confidence calculation unit configured to calculate a speech recognition confidence value which is a confidence value relevant to the speech recognition; and a control unit configured to calculate at least one behavioral decision function of a speech behavioral decision function associated with speech and a music behavioral decision function associated with music based on the noise-processing confidence value, the music feature value estimation confidence value, and the speech recognition confidence value and to determine behavior corresponding to the calculated behavioral decision function.