Introduction
Echo is heard between IP phones on the same IP network.
Core Issue
Echo is being introduced in the Digital Signal Processor (DSP) on the phone.
Resolution
To resolve this issue, update the phone loads offered by the Cisco CallManager.
There is no analog-to-digital conversion taking place in the network for calls between IP phones on an IP network. Therefore, the problem in such cases must be in the software or settings in the phones themselves.
Echo Cancellation is a feature that is almost always subject to improvement. However, ensure that you have at least the following phone loads that have quality improvements and tweaks of the DSP Acoustic Echo Canceller, and at least one other echo fix associated with Cisco bug ID CSCdv05279 - Echo on handset calls if volume over 75%, as shown:
- For Cisco CallManager 3.1: P00303010407
- For Cisco CallManager 3.2: P00303020205
- For Cisco CallManager 3.3: P00303030009
Known Fixed Releases
3.1(3.2)
3.1(3a)ES27c
3.1(3a)SPF
3.2(2.1)
3.3(2.10)
3.4(0.23)
Reference
