Impedance-matching a microphone lets an ordinary seismograph record acoustic signals undistorted.

Evidence

The pressure sensors were B&K model 4165 microphones with a nominal sensitivity of 50 mV/Pa. To avoid clipping, we reduced the signal output of the microphones by a factor of 1000 using a passive resistor bridge circuit, which also reduced the output impedance to 400 ohms. With the impedance matching bridge these microphones had electrical characteristics very similar to geophones and could be recorded by the digital seismograph without signal distortion. — Donald G. Albert, Michelle E. Swearingen, Frank E. Perron, and David L. Carbee, Low Frequency Acoustic Pulse…, 52

Categorization

• XREF: Connects to any seismic-refraction or snow-acoustics field setup where channel count and recording hardware constrain sensor choice.