Testing Conditions
Microphone performance is affected by operating voltage and load resistance. Standardized conditions are required to ensure consistent sensitivity measurements.
Key Parameters
1. Power Consumption
The working current of a microphone is primarily determined by the FET under VSG = 0 conditions. The standard working current typically falls between 100μA and 500μA.
2. Sensitivity
The ability of the microphone to convert sound pressure into an electrical signal, measured in V/Pa or dBV/Pa. Some companies use dBV/μBar.
3. Output Impedance
The output impedance is approximately 1-70% of the load resistance (RL).
4. Directionality & Frequency Response
- Omnidirectional: Equal sensitivity in all directions. The microphone is fully sealed except for the sound inlet hole, making it a pressure-sensitive type.
- Unidirectional: Higher sensitivity at 0° (front) and lowest at 180° (rear). It features acoustic ports on the PCB and internal sound-absorbing material.
- Noise-Canceling: A pressure-gradient type microphone without internal absorbing material, featuring a figure-8 polar pattern.
5. Frequency Range
- Omnidirectional: 50-12,000Hz or 20-16,000Hz
- Unidirectional: 100-12,000Hz or 100-16,000Hz
- Noise-Canceling: 100-10,000Hz
6. Maximum Sound Pressure Level (SPL)
The SPL at which distortion reaches 3%. Measured in dB SPL, where 20μPa = 0 dB SPL.
7. Signal-to-Noise Ratio (S/N)
The ratio of microphone sensitivity to self-noise, mainly influenced by the FET inside the microphone.
Microphone Testing Methods
Standardized testing procedures must be followed to evaluate microphone performance accurately.
