User Manual

Cisco High-Density Analog Voice and Fax Network Module

Configuration Tasks

Cisco IOS Release 12.2(2)XT and 12.2(8)T

Configuring Voice Activity Detection (VAD)

Voice activity detection (VAD) is configured on dial peers; by default it is enabled. For more

information, see the “Configuring Dial Plans, Dial Peers, and Digit Manipulation” chapter in the

Cisco IOS Release 12.2 Voice, Video, and Fax Configuration Guide, Release 12.2. Two parameters

associated with VAD, music threshold and comfort noise, are configured on voice ports.

If VAD is enabled, use the following commands to adjust parameter values associated with VAD,

beginning in voice-port configuration mode:

Fine-Tuning Analog Voice Ports

Normally, default parameter values for voice ports are sufficient for most networks. Depending on the

specifics of your particular network, however, you may need to adjust certain parameters that are

configured on voice ports. Collectively, these commands are referred to as voice-port tuning commands.

Note The commands, keywords, and arguments that you are able to use may differ slightly from those

presented here, based on your platform, Cisco IOS release, and configuration. When in doubt, use

Cisco IOS command help (command ?) to determine the syntax choices that are available.

The voice-port tuning commands are grouped into these categories and explained in the following

sections:

• Configuring Disconnect Supervision Commands (optional)

• Configuring FXO Supervisory Disconnect Tone Commands (optional)

• Configuring Timeouts Commands (optional)

• Timing Commands (optional)

• Voice Quality Tuning Commands (optional)

Full descriptions of the commands in this section can be found in the Cisco IOS Voice, Video, and Fax

Command Reference, Release 12.2.

Command Purpose

Step 1

Router(config-voiceport)# music-threshold number

Specifies the minimal decibel level of music played

when calls are put on hold. The decibel level affects

how voice activity detection (VAD) treats the music

data. Valid entries range from –70 to –30. When

used with VAD, if the level is set too high, the

remote end hears no music; if it is set too low, there

is unnecessary voice traffic. The default is –38.

Step 2

Router(config-voiceport)# comfort-noise

This parameter creates subtle background noise to

fill silent gaps during calls when VAD is enabled on

voice dial peers. If comfort noise is not generated,

the resulting silence can fool the caller into

thinking the call is disconnected instead of being

merely idle. The default is that comfort noise is

enabled.