GSM/GPRS Modules
GSM Module Audio Design Guide
GSM Module Audo Design Guide Confidential/Release 26 / 35
Figure 23：SPK THD
1. Horizontal axis is frequency, longitudinal axis is distortion and unit is %
2. Figure 23, the three colors represent three venders’ products. After comprehensive comparison, the
green one performs the best, and the blue one is second, and the red one is the worst.
2.8. Component of Microphone
It is recommended to use an electret microphone with a sensitivity of -42±3dB/Pa @ 2V（not less than
-44±3dB）and impedance of 2.2kΩ . If RF TDD noise is detected at the MIC, please contact MIC vendor
for product with better RF suppression capability. Furthermore, the microphone channel circuit can be
optimized to decrease TDD issue at MIC side.
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