The sensitivity of a microphone is the electrical response of its output to a given standard acoustic input. The standard reference input signal used for microphone sensitivity measurements is a 94dB sound pressure level (SPL) or a 1 kHz sine wave at 1 Pa (Pa, a measure of pressure). For a fixed acoustic input, a microphone with a higher sensitivity value has a higher output level than a microphone with a lower sensitivity value. Microphone sensitivity (expressed in dB) is usually negative, so the higher the sensitivity, the smaller its absolute value.
It is important to note the units in which the microphone sensitivity specification is expressed. If the sensitivities of the two microphones are not specified in the same unit, a direct comparison of the sensitivity values is not appropriate. The sensitivity of an analog microphone is usually specified in dBV, the number of dB relative to 1.0 V rms. The sensitivity of a digital microphone is usually specified in dBFS, which is the number of dB relative to the full-scale digital output (FS). For digital microphones, full-scale signal is the highest signal level the microphone can output; for Analog Devices MEMS microphones, this level is 120 dBSPL. See the Maximum Acoustic Input section for a more complete description of this signal level.
Sensitivity refers to the ratio of input pressure to electrical output (voltage or digital). For analog microphones, sensitivity is usually measured in mV/Pa, and the result can be converted to a dB value by:
Higher sensitivity doesn’t always mean better microphone performance. The higher the sensitivity of the microphone, the less margin it usually has between its output level and maximum output level under typical conditions (such as talking, etc.). In near-field (close talk) applications, highly sensitive microphones may be more prone to distortion, which often reduces the overall dynamic range of the microphone.
Post time: Aug-04-2022
