Electret microphones are widely used due to their compact size, reliability, and consistent performance. Understanding their parameters is essential for proper integration in various applications.
Sensitivity
Sensitivity defines the ratio of output voltage to the sound pressure acting on the diaphragm. It is measured in volts per Pascal (V/Pa) or millivolts per Pascal (mV/Pa). A higher sensitivity indicates a better response to weak sound signals.
Sensitivity level is often expressed in decibels (dB) using the formula:
LP = 20 log(P/P0), where P0 = 1V/Pa.
Example: For smartphone microphones, sensitivity typically ranges between -44 ± 2 dB.
Frequency Response
The frequency response curve shows how sensitivity changes with frequency. In communication devices, the focus is on the speech range (200–4000 Hz), ensuring clear and intelligible audio. A flat response curve within this range is essential.
Output Impedance
Output impedance affects matching and transmission efficiency. Electret microphones generally have low impedance (<700 Ω). For voltage amplifiers, the input impedance is usually 1–5 times the microphone's output impedance.
Operating Voltage
As active components, electret microphones require an external power supply, typically between 1.5V and 10V. Sensitivity can vary slightly with voltage changes; a 3V change may affect sensitivity by approximately 0.8 dB.
Signal-to-Noise Ratio (SNR)
SNR measures the microphone's ability to distinguish sound signals from background noise. Higher SNR values, generally ≥60 dB for omnidirectional microphones, are preferred. Factors affecting SNR include electronic noise, diaphragm thermal disturbances, and external electromagnetic interference.
Electret microphones offer reliable performance across various applications. Understanding their specifications ensures optimal usage in devices like smartphones, audio equipment, and communication tools.
