Pressure-gradient Microphone

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