FIGS. 7 and 8 are each a block diagram depicting another example of the structure of the personal authentication device in this exemplary embodiment. As depicted in FIGS. 7 and 8, the position of the noise/device property removal means is not limited to be subsequent to the acoustic signal observation means 102. As an example, the noise/device property removal means may be located subsequent to the acoustic property calculation means 103, as depicted in FIG. 7. As another example, the noise/device property removal means may be located subsequent to the feature extraction means 104, as depicted in FIG. 8. FIG. 7 depicts noise/device property removal means 202, as an example of the noise/device property removal means located subsequent to the acoustic property calculation means 103. FIG. 8 depicts noise/device property removal means 203, as an example of the noise/device property removal means located subsequent to the feature extraction means 104.

In these examples, the noise/device property removal means 202 removes noise and device property from the acoustic property calculated by the acoustic property calculation means 103, and the noise/device property removal means 203 removes noise and device property from the feature value calculated by the feature extraction means 104.