Microphone experiments and applications in exploration seismology

Abstract

Coupling phenomena associated with energy conversion at the air-ground interface can be better understood if pressure levels and particle velocity, displacement or acceleration amplitudes are recorded in the field. In exploration seismology, the air pressure-ground motion relationship is essential to understand the coupling mechanism of airassociated noise into the geophones. The CREWES Project at the University of Calgary undertook two air-pressure recording experiments in western Canada to investigate using air-pressure data (from microphones) to attenuate aircoupled noise in geophones during two different seismic acquisition projects. A multichannel median filter was applied to the LMO-corrected microphone data to enhance the strong air blast arrival and allowed us to study our recorded data in terms of sound propagation and attenuation, power spectra and signal consistency. Adaptive filtering techniques produced reasonable estimates of the embedded geophone noise using a reference noise input (i.e. pressure data from several microphones). We had success in suppressing the 60 Hz interference by using the Least-Mean Squares (LMS) algorithm in a Finite-Impulse Response adaptive filter. The results are quite encouraging and more complex adaptive filter algorithms and other filtering techniques are under study.