Pressure-Gradient Microphone

A microphone in which both sides of the diaphragm are exposed to the incident sound and the microphone is therefore responsive to the pressure differential (gradient) between the two sides of the membrane. Sound incident parallel to the plane of the diaphragm produces no pressure differential, and so pressure-gradient microphones have characteristically figure-of-eight directional characteristics. Also called "velocity microphone", since the output voltage is proportional to the air particle velocity.