The Tone On Hold parameter specifies the number of seconds between every two hold tones played when a call is put on hold. Its effect on Media Gateway Control Protocol (MGCP)-based devices differs from other devices:
For MGCP-based devices, if this value is 0 or 200,000, it completely disables the hold tone on that device. Any other value enables the hold tone on MGCP-based devices when the caller is put on hold.
For all other (non-MGCP-based) devices, if this value is 0, the held device plays the hold tone only one time when the caller is put on hold; if the value is 200,000, no hold tone is played at all. Otherwise, the held device plays the hold tone every so many seconds (specified by this value) repeatedly. If the value is less than five seconds, the device raises it to five seconds.
There is no way to turn down the Tone on Hold volume. There is not a service parameter in Cisco CallManager for adjusting this. Cisco CallManager sends a notification event to the end device telling the device to play the tone, and the Digital Signal Processor (DSP) on that device actually generates the tone.
For example, using Tone on Hold for an IP phone-to-IP phone call, the Cisco CallManager sends an "SCCP StationD packet StartTone tone=53(HoldTone)" and the DSP in the phone that has been placed on hold plays the tone on the phone. Cisco CallManager send this message to the phone every n seconds based on what is configured for the Cisco CallManager service parameter ToneOnHoldTime. If an IP phone puts a caller on hold through a gateway, then Cisco CallManager sends either an H.323 message or MGCP message, depending on how the gateway is configured, indicating to the gateway to play the hold tone to the Plain Old Telephone Service (POTS) leg of the call. Then the DSP in the gateway generates a tone to the POTS leg, and the caller hears the hold tone.
However, to turn off Tone On Hold, perform these steps:
Go to The CCMAdmin page.
Select Service > Service parameters.
Select CallManager IP as the server and CallManager as the service.
On the service parameters configuration page, go to the Edit menu and select Tone On Hold.
Change the value of the Tone On Hold Timer to 200,000 seconds and update.
Make test calls.
This is an alternative procedure:
Log in to the CCMAdmin page.
Select Service > Media Resource > Music on Hold Server.
Click the MoH server.
Change the Run Flag* field to No and click Update.
Another way to accomplish this is to create an silent .wav file, and assign that file as an audio source and assign that audio source to the phones. This file has nothing but silence, so nothing would be played in Music on Hold (MOH).
For related information on Tone On Hold, refer to these documents: