Electroacoustic Study on Detecting Drummy Rock

Abstract

This paper describes the method for detecting “loose” or “drummy” rock, analyzing a sound of rock electroacoustically.
In this study the authors divided each sound every one-third octave through thirteen filters of which the frequencies are 4000 to 6, 300cs, and tried to discriminate better between solid and drummy rock, using “Integrator”. Here “Integrator” is an instrument made to measure electronically an equivalent to the area surrounded with the envelope of the wave form and the axis of the time.
By this method the following results were obtained.
Applying this method to sounds of several kinds of rocks, solid and drummy rocks of them were generally discriminated well; for example, in the case of slate the ratio of the mean value of the quotients of the areas of the filtered wave forms divided by the areas of the unfiltered wave forms of drummy rocks to that of solid ones was even more than 20db., when the filter frequency was 500c/s.