Microsoft Lync Edition Administrator’s Guide for SIP-T2_Series and T4_Series IP Phones2022. Select the desired value from the pull-down list of VAD.3. Click Confirm to accept the change.Comfort Noise Generation (CNG) is used to generate background noise for voicecommunications during periods of silence in a conversation. It is a part of the silencesuppression or VAD handling for VoIP technology. CNG, in conjunction with VADalgorithms, quickly responds when periods of silence occur and inserts artificial noiseuntil voice activity resumes. The insertion of artificial noise gives the illusion of a constanttransmission stream, so that background sound is consistent throughout the call and thelistener does not think the line has released. The purpose of VAD and CNG is to maintainan acceptable perceived QoS while simultaneously keeping transmission costs andbandwidth usage as low as possible.NoteFor example, A is talking with B.A: VAD=1, CNG=1B: VAD=0, CNG=1If A mutes the call, since VAD=1, A will send CN packets to B. When receiving CNpackets, B will generate comfortable noise.If B mutes the call, since VAD=0, B will not send CN packets to A. So even if CNG=1 (B),A will not hear comfortable noise.VAD is used to send CN packets when phone detect a "silence" period; CNG is used togenerate comfortable noise when phone receives CN packets from the other side.
