How to Solve Echo

VoIP Settings to Reduce Echo

Man with VoIP troubleshooting folder.The following are settings that can be used to reduce echo in either Asterisk or an ATA (Analog Telephone Adapter) device. These configurations can be located in the software settings, if you are able to access the internal pages. Whether you are using a VoIP ATA or are using Asterisk installed on a server, you should be able to reduce voice echo by tweaking these configuration settings. The following steps generally work well, but are not a panacea to rid echo. If choosing a FXO or T1 card, obtain one with built in echo cancellation from the manufacturer.

Try the following transmit and receive gain values to Reduce Echo

  • The transmit and receive gain settings in Asterisk (txgain and rxgain) can be set to negative values. These settings will act to reduce the sound volumes, but will also produce a more acceptable echo. Set txgain = –10 (or thereabouts) which should have a sufficient call volume with little perceived echo.
  • For an Asterisk system, get cards, like T1 or FXO, with an echo cancellation chip built onto the card. In the long run the additional expense will be greatly appreciated by the better call quality.
  • Make sure that no other device, including USB ports are using the same IRQ as your gateway card. The installed card should be the only device that can use that particular IRQ.
  • If the particular echo that you are experiencing is the type that results from leakage from the incoming voice to the outgoing voice, then some manufacturers of ATAs have TX and Rx Gain adjustments that can be set for the analog FXO port.
Lower transmit gain levels can help reduce VoIP echo in analog telephone adapters.
  • Enter the edit page of the device. Locate the Tx Gain and Rx Gain settings. Start by lowering the values, then saving your changes. Test by making calls until the echo is moderated.
The default values set by the factory on some Cisco/Linksys ATAs can be too high.

The default settings for TX gain on the Cisco/Linksys PAP2T analog telephone adapter can come from the factory slightly high which can cause echo.

  • Try adjusting the ATA's FXS Port Input Gain and FXS Port Output Gain, one setting at a time, using increments of three to the approximate values of -1 and -11. Although these values will vary dependent on network architecture and other hardware in use, you may find these values will help to eliminate echo and still produce an adequate volume.
  • For Asterisk deployments use zapata.conf files to adjust the rxgain and txgain.

Echo in VoIP, once a major problem, has been eliminated through excellent use of echo cancellation hardware and software settings.

Checking Sangoma Cards for Echo Cancellation

To Verify that a Sangoma Card has hardware echo cancellation type the following in your Linux command line: wanrouter hwprobe
At the end of the output if you see either: HWEC=0, which means No Hardware Echo Canceller or HWEC=anything, (but not 0), that you have Hardware Echo Cancellation.