A satisfactory sound volume sensation from a hearing point of view can be obtained, and an effective sound volume correction operation can be obtained with an algorithm as simple as possible. Correction step 0 (correction function off, level correction value 0) to correction step 16 (level correction value—16 dB) are defined. When a first condition that is defined in such a manner as to correspond to a state in which distortion occurs is satisfied, the correction step is made to proceed by one step from the current correction step (−1 dB is added to a level correction value). When a second condition that is defined in such a manner as to correspond to a state in which distortion does not occur is satisfied, the correction step is made to return by one step from the current correction step (−1 dB is subtracted from the level correction value).