AudioCodes Mediant 500 MSBR, User Manual

Page: 165 / 1248

Version 7.2 165 Mediant 500 MSBR
User's Manual 17. Media
17 Media
This section describes the media-related configuration.
17.1 Configuring Voice Settings
The section describes various voice-related configuration such as voice volume and DTMF
transport type. For a detailed description of these parameters, see Configuration
Parameters Reference on page 983.
17.1.1 Configuring Voice Gain (Volume) Control
The device allows you to configure the level of the received (input gain) Tel-to-IP or IP-to-
IP signal and the level of the transmitted (output gain) IP-to-Tel or IP-to-IP signal. The gain
can be set between -32 and 31 decibels (dB).
The following procedure describes how to configure gain control through the Web interface.

To configure gain control through the Web interface:
1. Open the Voice Settings page ( Setup menu > Signaling & Media tab > Media folder
> Voice Settings ).
Figure 17-1: Configuring Voice Volume
2. Configure the following parameters:
•
'Voice Volume' ( VoiceVolume ) : Defines the voice gain control (in decibels) of the
transmitted signal.
•
'Input Gain' ( InputGain ): Defines the PCM input gain control (in decibels) of the
received signal.
3. Click Apply .
4. Click Apply .
17.1.2 Configuring Echo Cancellation
The device supports adaptive linear (line) echo cancellation according to G.168-2002.
Echo cancellation is a mechanism that removes echo from the voice channel. Echoes are
reflections of the transmitted signal.
In this line echo, echoes are generated when two-wire telephone circuits (carrying both
transmitted and received signals on the same wire pair) are converted to a four-wire circuit.
Echoes are reflections of the transmitted signal, which result from impedance mismatch in
the hybrid (bi-directional 2-wire to 4-wire converting device).
An estimated echo signal is built by feeding the decoder output signal to an RLS-like
adaptive filter, which adapts itself to the characteristics of the echo path. The ‘estimated
echo signal’ (the output of this filter) is then subtracted from the input signal (which is the
sum of the desired input signal and the undesired echo) to provide a clean signal. To
suppress the remaining residual echo, a Non Linear Processor (NLP) is used, as well as a
double-talk (two people speak at the same time) detector that prevents false adaptation
during near-end speech.