<p>An audio signal (10) is inputted to a power adjusting unit (1), a vowel processing unit (2), a consonant processing unit (3), and a backup unit (5). The power adjusting unit (1) obtains a power in the vicinity of the cut-off band (such as 7 kHz) of the audio signal (10). The vowel processing unit (2) generates a harmonic sound of the vowel component according to audio information (pitch) of the audio signal (10). The consonant processing unit (3) generates a harmonic sound of the consonant component according to the audio information in the audio signal (10). A complementary component generation unit (4) generates a high-range component of the audio signal (10) according to the power of the audio signal (10). The backup unit (5) adds the high-range component to the audio signal (10) and generates a complementary audio signal (50) having a complemented high-range component.</p>
