DRAFT
© 2003 - 2005 Sipura Technology, Inc
Proprietary (See Copyright Notice on Page 2)
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Voice Activity Detection with Silence Suppression & Comfort Noise
Generation
Voice Activity Detection (VAD) and Silence Suppression is a means of increasing the number of calls
supported by the network by reducing the required bi-directional bandwidth for a single call. VAD uses a
very sophisticated algorithm to distinguish between speech and non-speech signals. Based upon 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
2-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 since the silence
packets are not being transmitted across the network.
Configurable Dial Plan with Interdigit Timers
The SPA has three configurable interdigit timers:
•
Initial timeout (T) = handset off hook, no digit pressed yet.
•
Long timeout (L) = one or more digits pressed, more digits needed to reach a valid number (as
per the dial plan).
•
Short timeout (S) = current dialed number is valid, but more digits would also lead to a valid
number.
Please see Section 10 for complete Dial Plan implementation details.
