[FAQ] Changing the comfort noise on a Polycom VVX Business Media Phone

[SteffenBaierUK]

In certain situations or scenarios it may be preferable to change the factory default of comfort noise utilizing a Microsoft Lync or Skype for Business Server.

UC Software 5.4.2 or later added the below.

Parameter Recommendation	Parameter Range	Default Value	Result
voice.cn.hs.enable="1"	0 or 1	0	Enables the in-band comfort noise fill
voice.cn.hs.attn="35"	90 to -90	0	Sets the in-band comfort noise attenuation (lower numbers are louder, we suggest no lower / louder than 35)
voice.vadEnable="0"	0 or 1	0	Disables VAD Tx – VAD Rx CNG packets will still be properly received to synthesize local comfort noise
voice.vadRxGain="10"	20 to -20	0	Boosts the VAD CNG synthesis level by 10 dB – subjectively matches the customer site RTP capture
voice.vadTxGain="-10"	20 to -20	0	Reduces the VAD CNG packet payload value by 10 dB – effectively prevents the synthesis boost in voice.vadRxGain from changing the level in a VVX to VVX call
voice.vadRxGain == -voice.vadTxGain			Restores default behavior
G.722 calls, vadTxGain and vadRxGain have no effect (expected)
voice.plcCnEnable="1"	0 or 1	0	Enables local comfort noise generation when far end stops sending RTP and no CN packet is sent
voice.plcCnGain="0"	20 to -20	0	Changes the loudness of local comfort noise generation when voice.plcCnEnable is set to 1