Piezoelectric borehole microphone for seismic signals - has twin piezoceramic discs locked in borehole by wedge contact pieces

摘要

The piezoelectric microphone for measuring mechanical vibrations consists of a twin assembly of piezoceramic discs with rounded contact pieces bonded to them on both sides. One of the contact pieces is split to form two wedges. The microphone can be wedged diametrally at a desired spot in a borehole by applying a pull one one wedge and a push on the other by rods, extending to outside the borehole. This creates a simple, yet robust borehole microphone of high sensitivity which is free from the limited frequency range and parasitic resonance of geophones and from the vibration suppression of hydrophones.