Key parameters for Electret Condenser Microphone (ECM)
There are several key parameters that are used to describe the characteristics of an Electret Condenser Microphone (ECM).
Sensitivity: Since a Electret Condenser Microphone is a transducer that converts acoustic energy into electric energy, one of the most important characters is the conversion ratio, i.e. what is the electrical response level at its output when given a certain level of acoustic input. This character is indicated as Sensitivity. It can be measured with unit mV/Pa, but normally a standard reference ratio 1V/Pa (1000mV/Pa) is used to convert the sensitivity to a decibel value with the following equation:
An Electret Condenser Microphone with a higher sensitivity value will have higher electrical output than a Electret Condenser Microphone with a lower sensitivity value, given the same sound pressure input. Since sensitivity in decibels (dB) is typically a negative number, a higher sensitivity actually shows as a smaller absolute value.
Signal-to-Noise Ratio (SNR): When an Electret Condenser Microphone works, there will be noise generated both from the microphone element and the internal preamplifier. These are unwanted signals that affect the accuracy of the output, so Signal-to-Noise Ratio (SNR) is defined to indicate how much desired sound is present in the electrical output signal as opposed to unwanted noise. It is measured as the difference in decibels between the noise level and a standard 1kHz 94dBSPL reference signal. The noise level is usually calculated by A-weighting over a 20kHz bandwidth in order to include the different perception effect of human ear to different sound frequencies, so the unit of this parameter is normally shown as dB(A).
Frequency Response: This curve indicates the Electret Condenser Microphone output level across the whole frequency band, usually being normalized with the reference level at 1kHz to 0dB.
Maximum Input Sound Pressure Level: This parameter indicates the maximum sound pressure level the Electret Condenser Microphone can receive without being damaged.
Current Consumption: This parameter indicates the maximum current consumption of the Electret Condenser Microphone when it is in normal operating mode. This parameter is key especially for applications where energy consumption is paramount.
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