3Com NBX 100 Administrator's Manual page 281

another NBX device receives this indicator, it generates and inserts white
noise until it receives the next frame that contains audio data. If you
enable Silence Suppression, a careful listener might notice a difference in
audio quality. The background white noise generated by the receiving
phone is subtly different from the silence in an audio stream.
What is Echo Suppression?
Echo suppression is a method of reducing or eliminating audio feedback
(echo). The NBX system has internal mechanisms to deal with echo,
however, external conditions can induce echo that is beyond the scope of
the internal mechanisms. Echo on external calls is usually due to older
equipment at the phone company's central office. Echo can also be
caused by user behavior. If a caller has the phone volume turned up and
then that caller does not hold the phone flush to their ear, the handset's
mouthpiece can pick up audio from the ear piece, which causes echo.
To enable audio settings, select System Configuration > System Settings >
Audio Settings.
Table 56 System Settings Audio Settings Dialog Box Fields
Field Purpose
Bandwidth Controls reduce the number or the size of packets transmitted during
a conversation. You can enable bandwidth controls to help reduce network
congestion, however, enabling bandwidth controls can compromise audio quality.
System-wide Reduces the number of packets transmitted during a
Silence Suppression conversation by not transmitting packets during times of
silence during a conversation. Enabling this check box enables
silence suppression on all conversations.
System-wide Implements silence suppression on calls carried over Virtual Tie
Silence Suppression Lines.
on VTL Calls
Audio Compression Enables ADPCM compression, which reduces the number of
on VTL Calls packets as compared to the normal PCM format of audio data
on virtual tie line calls. Enable this check box only if you have
network congestion on the VTLs that connect your NBX
systems and those issues have not been resolved by enabling
System-wide Silence Suppression or System-wide Silence
Suppression on VTL Calls.
System Settings 281