A pressure-gradient microphone is one that responds to a difference in pressure at two closely spaced points. A common example of this type of microphone has a diaphragm, both sides of which are exposed to the sound wave. Such a construction is shown in Fig. 5.4
If a pressure-gradient microphone is placed in the cavity of Fig. 5.2a
, there will be no net force acting on the diaphragm and its output will be zero. This happens because there is no pressure ...