GSM/GPRS Modules
GSM Module Audio Design Guide
GSM Module Audo Design Guide Confidential/Release 23 / 35
In these five paths, internal air-path and direct air-path are the first influential factors. Other three factors
(vibrations through casework, vibrations through PCB, distant echoes) are secondary.
How to deal with echo issue from internal air-path:
Separating microphone from internal space of chassis by foam or rubber ring can effectively suppress the
inner echo interference. Figure 20 shows recommended design for microphone socket.
Figure 20：Microphone Socket Design
The best installation way of microphone socket is to encase microphone by silicone cover except for front
cavity, and design a cylindrical hole whose center is the exit hole inside the chassis, make the microphone
with silicone cover just fit the cylindrical hole, so as to only let voice enter into microphone from the exit
hole, and not from leak of chassis interior. Certain air space room should be reserved in the front cavity of
microphone as it is necessary for good microphone performance.
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