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Electret microphone
Charasteristics
Image 2. Electret microphone (https://cdn.sparkfun.com//assets/parts/1/7/6/9/08635-03-L.jpg)
Electret microphone is omnidirectional. This meas that it can hear from all directions. Transistor works as transducer in the heart of the electret microphone. Electret microphone sensitivity is defined in datasheet as "(- 46 ± 2.0, ( 0 dB = 1V / Pa ) at 1K Hz)". Operating temperature the electret microphone is working is -20 to 60 degrees. Frequency rate is 100 - 10,000 Hz. Current depend on sound level. Maximum current is 0.5mA.
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Interface electronic circuits
Image 2. Eletritet microphone (http://hades.mech.northwestern.edu/images/thumb/8/80/ElectretMicrophone.gif/300px-ElectretMicrophone.gif)
Electret microphones have two legs, one is ground and another is voltage. Electret microphone can be tested by oscilloscope to see what kind signal is coming out from different sound levels. To get results the signal is amplified from ten to hundred times.
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