Acoustic tapping survey for cavities using wavelet transform signal analysis

Fumio WATANABE and Keichi KASAHARA

Nippon Geophysical Prospecting Co.,Ltd.
2-2-12, Nakamagome, Oota-ku, Tokyo, 143-0027, Japan
E-mail: fwatanabe@n-buturi.co.jp

Abstract

The judgment whether cavities are in existence or not by tapping test is very conventional, but we cannot get objective conclusion. For more objective we replace auditory judging by visual inspection of the signal, especially scalogram (spectrum) of the recorded sound wave after the wavelet transform is rather effective. In this manner, we hit with a hammer the inside wall of the object from place to place. If we meet a portion with a cavity in the soil or rock behind the wall etc., then the scalogram would appear abnormal, in comparison with other places buried tightly.

This paper introduces our wavelet transform analysis technique regarding its principle background, instrumentation, together with successful examples of field work.

raeg99@tansa.kumst.kyoto-u.ac.jp

Last modified: Wed Dec 1 08:41:37 1999