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Microphone Directivity

January 5th Fact-of-the-Day

All microphones respond primarily to changes in air pressure or air velocity, but not to both unless they internally contain two different types of transducers, which is very rare. The distinction is important to microphone directivity. Pressure-responding microphones respond to absolute changes in air pressure caused by passing sound waves. They always have non-directional response-sensitivity patterns. In contrast, velocity-responding microphones are pressure-gradient transducers that respond to differences in air pressure between two sides of a diaphragm. Velocity microphones always have directional polar response-sensitivity patterns. Furthermore, sound waves propagating toward the back of a velocity microphone diaphragm produce an electrical output signal that is out of phase with respect to the output produced by sound waves propagating toward the front. ©2005 Martek International All rights reserved.

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