FIGS. 13(a) and 13(b) are explanatory diagrams depicting an example of a transmission acoustic signal obtained by superimposing, on an acoustic signal of music, another acoustic signal for the purpose of compensating for a low-power component of the frequency components in the musical sound. FIG. 13(a) depicts the spectrum power of the original music. FIG. 13(b) depicts the spectrum power of the transmission acoustic signal obtained by adding white noise to the original music. FIGS. 13(a) and 13(b) both depict a value obtained by Fourier transform, with the horizontal axis representing frequency and the vertical axis representing spectrum power in logarithmic axes. As depicted in FIGS. 13(a) and 13(b), the low-power portion is compensated for by adding white noise or the like to the original music.

The foregoing exemplary embodiments may be used in combination. Moreover, although the foregoing exemplary embodiments each describe an example where the personal authentication device operates alone, the personal authentication device may be used in combination with another device. As an example, a personalization system that provides a service different for each person based on a result of specifying a person using any of the personal authentication devices described above may be provided. The system may include, in addition to the personal authentication device, service provision means (not depicted) for providing a service different for each person based on a specification result output from the personal authentication device.