Silence Suppression

Voice activity detection (VAD), often referred to as silence suppression, is a software application used to free up bandwidth on networks using voice over IP (VoIP) (Rouse, 2008). When no activity is detected for the period of time the application is configured for, the software notifies the Packet Voice Protocol, which prevents the transmission of the silence data (Ellis, Pursell, Rahman). Due to the break in transmission of data, voice clipping and poor voice quality can become a factor when silence suppression is working (Ellis, Pursell, Rahman).

Because the human speech activity is filled with pauses between words and sentences, and voice conversations are one-way at a time (half-duplex); bandwidth can be saved by ceasing transmission during these silent periods (Ellis, Pursell, Rahman). The Internet today is in high usage with data transfer. Without silence suppression, transmission speeds and networks would suffer from congestion due to useless packets traveling throughout the network (What is silence suppression, 2003). Silence suppression is most beneficial to businesses using Internet voice applications because is keeps useless data from clogging up the network and capacity (What is silence suppression, 2003).

The Internet Engineering Task Force (IETF) created the Internet standard RFC 3389 to deal with silence suppression in the form of comfort noise (CN) (Zopf, 2002). Comfort noise is, essentially, a description of the sounds or noises picked up by the microphone of the listening party, and sent to the remote end to avoid complete dead air (Ellis, Pursell, Rahman). Silence suppression can also forward comfort noise to a remote IP telephone or gateway (Rouse, 2008).

While researching references, I began to realize that, while on a mobile smartphone, the characteristics associated with silence suppression have occurred. If I talk to someone with the radio or television playing in the background, when the person stops talking, the sound clips in and...