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BGS2-E produces sporadic loud noise after accepting incoming voice call | Telit Cinterion IoT Developer Community

tge's picture

April 5, 2017 - 4:26pm, 6355 views

We use BGS2-E with Revision 02.000 for our mobile gateway with tip/ring interface.
At the interface there is a small  PABX connected. But we may also cause this problem with simple resistor.

The selected audio hardware therefore is set to AT^SNFS=6. 
Microphone path parameters are set to AT^SNFI=0, 32767, which gives "normally" a good audio result.

But now we get more and more reports about sporadic loud noise after the gateway accepts an incoming voice call. The loudness changes and sometimes there is absolutely no noise (with same hardware). To be sure we checked the MIC input but this is not the cause.

Nevertheless we can mute this noise with AT+CMUT. After unmute the noise is still active.

The only way we have found to stop the noise is either to send a tone with AT^SNFG=1000,1000,100 or another loud tone or voice passes the audio path.

Any idea what we can do against this noise? Has is something to do with the internal noise reduction or echo cancellation algorithm?

Thanks in advance!