Airborne sound to seismic coupling: Background for development of the models

Abstract

The initial measurements of the acoustic‐to‐seismic coupling phenomena using loud speakers as sound sources were made by the University of Mississippi and Waterways Experiment Station. For these measurements, a speaker was suspended from a crane, the sound level in the farfield was measured with a microphone above the surface, and the geophone response was measured below the surface. The results of this work largely indicated that the geophone had a response 1000 times greater than one would expect from calculations based upon simple acoustic transmission through a boundary between two perfect fluids. Another finding was that the transit times from speaker to microphone and speaker to geophone were approximately the speed of sound in the air. Success in our lab with water‐saturated sediments suggested the application of the Biot model to the ground. Microphones were developed that were used as a pore fluid probe in the soil, and the attenuation and phase speed in the pore fluid were measured. This work led to the understanding of the commonly assumed locally reacting property of the ground.