Record using Monitor - bit rate

[nmigliaro]

Hello,

I am using monitor application in Asterisk. Im seeing that created audio file has this configuration
- 16 bit
- 8000 hz
- 128 kbps

I need to change bit codification from 16 bit to 8 bit.
I tried SOX sox IN-FILE.wav -b 8 OUT-FILE.wav but after the transformation there is a background noise.

My question is:
1 - Is it possible to change something in Asterisk to force 8 bit codification instead of 16 bit in order to avoid re-codification

2 - Is there another parameter that can be set up in SOX for eliminationg this background noise.

Thank you in advance.

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exten => 7000,1,Verbose(test record)
same => n,answer()
same => n,monitor(wav,${EXTEN},m)
same => n,SayDigits(1234567890)
same => n,stopmonitor()
same => n,Hangup