A transducer that changes the physical motion of air molecules into an equivalent electrical signal that can be processed by a sound measurement system such as a sound level meter. Different devices have different frequency responses and sensitivities. All other things being equal a smaller diameter microphone diaphragm produces a lower electrical output signal for a given sound pressure. The sensitivity of a microphone is given as the number of Volts obtained for a reference sound pressure. Typical examples are 10 mV/Pa for a general-purpose microphone capsule.