GSM/GPRS Modules
GSM Module Audio Design Guide
GSM Module Audo Design Guide Confidential/Release 24 / 35
Figure 21 shows recommended design for speaker socket.
Figure 21：Speaker socket design
A good way to suppress the internal echo path is to seal the rear cavity of receiver, which is usually
expensive. The rear cavity of receiver and speaker is important for good voice quality. A sealed rear cavity
with sufficient space could produce a good voice output. An 8Ω speaker is often big and difficult to give an
independently sealed rear cavity for it. However, sealing microphone socket in chassis is always useful.
Furthermore, the whole chassis must be sealed as far as possible. If there is any unavoidable leak hole,
keep it far away from microphone. If the leak hole is close to microphone, the voice coming from the hole
could be picked up by MIC, and then leads to echo at the far end. If the leak hole is close to speaker, the
output voice quality could be aggravated at certain extent.
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