Cisco SPA2102-SF Administration Guide - Page 60

Configuring Voice Services Silence Suppression and Comfort Noise Generation 4 Silence Suppression and Comfort Noise Generation Voice Activity Detection (VAD) with Silence Suppression is a means of increasing the number of calls supported by the network by reducing the required bandwidth for a single call. VAD uses a sophisticated algorithm to distinguish between speech and non-speech signals. Based on the current and past statistics, the VAD algorithm decides whether or not speech is present. If the VAD algorithm decides speech is not present, the silence suppression and comfort noise generation is activated. This is accomplished by removing and not transmitting the natural silence that occurs in normal two-way connection. The IP bandwidth is used only when someone is speaking. During the silent periods of a telephone call, additional bandwidth is available for other voice calls or data traffic because the silence packets are not being transmitted across the network. Comfort Noise Generation provides artificially-generated background white noise (sounds), designed to reassure callers that their calls are still connected during silent periods. If Comfort Noise Generation is not used, the caller may think the call has been disconnected because of the "dead silence" periods created by the VAD and Silence Suppression feature. Silence suppression is configured in the Line and PSTN Line tabs. See "ATA Routing Field Reference," on page 105. Cisco Small Business ATA Administration Guide 60