When purchasing microphone components (MICs), many buyers may struggle to understand the concept of "sensitivity." Here's a simple explanation to clarify this important parameter.
What is Microphone Sensitivity?
Microphone sensitivity refers to the electrical signal output generated by the microphone in response to a specific sound pressure level. Higher sensitivity indicates that the microphone has a more efficient sound-to-electricity conversion and can detect weaker sound signals effectively.
Technically, sensitivity is measured by applying a sound pressure of 0.1 Pa (or μBar) and determining the voltage output by the microphone. For example, a microphone with a sensitivity of 1mV/μBar means it outputs 1mV when subjected to 1μBar of sound pressure.
Decibel (dB) Representation
Sensitivity is often expressed in decibels (dB). Common sensitivity ranges include -48 dB to -66 dB (domestic standard) and -34 dB (international standard). For reference, -34 dB internationally is equivalent to -54 dB domestically. This means that typical microphones range from -28 dB to -48 dB.
Sensitivity is defined based on the voltage output when a microphone is subjected to 1 Pa (94 dB SPL) of sound pressure. For instance, a microphone with a sensitivity of -30 dBV/Pa is more sensitive than one with -42 dBV/Pa.
Calculating Sensitivity
Microphone sensitivity is calculated as the logarithmic ratio of the output voltage to a reference voltage, defined as: Lm = 20log(Vm/Vs), where Vs = 1V and Vm is the output voltage at 1 Pa sound pressure.
Additionally, sensitivity in dB can also be expressed as dB/V or dB/bar. The relationship between these units is: -30 dB/bar = -50 dB/V. Microphones used in headsets typically have lower sensitivity (below -50 dB/V) to suit their applications.
Factors Influencing Sensitivity
Sensitivity is a fixed specification based on standard bias testing. Manufacturers can enhance sensitivity by modifying materials or production processes. However, users should avoid incorrect biasing during operation, as it can lead to distortion, bandwidth compression, and reduced sensitivity.
