GAO's Voice Activity Detector (VAD), Comfort Noise Generator (CNG) software is used to reduce the transmission rate during silence periods of speech. Systems allowing discontinuous transmission are based on a Voice Activity Detection (VAD) algorithm and a Comfort Noise Generator (CNG) algorithm that allows the insertion of an artificial noise during silent intervals of speech.
This feature is necessary to avoid noise modulation introduced when the transmission is switched off. If the background acoustic noise that was present during active periods abruptly disappears, this very unpleasant noise modulation may even reduce the intelligibility of the speech. The purpose of the VAD is to reliably detect the presence or absence of speech and to convey this information to the CNG algorithm. The purpose of the CNG algorithm is to create a noise that matches the actual background noise with a global transmission cost as low as possible.
For a complete list of GAO's Telephony Software products, please see GAO's Telephony Software.