Hack39.Eliminate Echo and Noise


Hack 39. Eliminate Echo and Noise

Improve Skype's voice quality with these tips for echo cancellation and noise reduction.

Works with: all versions of Skype.

Echo and noise are such common problems for Skype users that I would be remiss not to provide a hack that addresses the problem. While the symptoms of echo and noise during a conversation are all too apparent, their causes and remedies are often quite the opposite. The tips in this hack should help you not only track down the cause, but also fix the problem.

A lot of the more up-to-date sound hardware has built-in echo cancellation and noise reduction, often implemented through digital signal processing (DSP). This is particularly true for array microphones. Having decent sound hardware is always a good investment for the Skype user. So, depending on your budget, upgrading your sound hardware in the face of persistent and incurable echo and noise is a worthwhile consideration, particularly if the remainder of this hack doesn't cure the problem.

Also worthy of some research on your part is whether your operating system, or sound card, or other sound hardware has echo cancellation and noise reduction built in. If it does, it may, or may not, be enabled by default.

As for any problem, you should first try to isolate it. Test your sound system outside of Skype (see "Test Your Sound System" [Hack #25]). If you still have echo and/or noise problems outside of Skype, there's something wrong with your sound setup. Otherwise, you know the problem is with Skype.

If the problem is with Skype, try some of these suggestions of what to do to fix things:


Symptom: echo

Fix: if you experience echo problems during a call, before hanging up tell the other party to test his setup by calling the echo123 service. After hanging up, you should likewise test your setup by calling echo123. This way, you can find out who actually has the echo problem: you or the other party. If both you and the other party have no echo problems when calling echo123, the next thing to do is to call a different Skype contact for which you know you've not had echo problems in the past. If echo is still a problem for you, try turning down your speaker volume and/or moving the microphone further away from the speaker. On laptops, the proximity of the built-in microphone to the built-in speaker is fixed, so in that case, you might want to try a headset instead. One cause of echo not related to your sound setup is data packet loss associated with your Internet connection. Beyond trying to call at different times (when Internet traffic congestion might be less of a problem), there's not much you can do about this. A tool such as PingPlotter (http://www.pingplotter.com/) may help isolate this cause of echo. Activity on your computer that consumes Internet bandwidth and resources may also be a cause of echo. If you are web browsing, listening to streaming music, downloading a filebasically, doing anything that consumes bandwidthand you're calling with Skype at the same time, try stopping the non-Skype activities and see if that improves the echo problem. The least likely cause of echo is the way in which Skype routes your calls. You can force Skype to route your calls differently by deleting the Skype super-node list it maintains in shared.xml. You can do this by stopping Skype from running, deleting shared.xml, and then restarting Skype. On restarting, Skype will build a new shared.xml file with a different super-node list.


Symptom: distorted sound and/or echo

Fix: Skype can sometimes overcompensate for your volume control as part of its effort to set your sound system's gain automatically. In config.xml, find the automatic gain control tag, <AGC> (there are two entries, one under the parent tag <Call> and the other under <General>), and set its value to 0that is, set both entries to <AGC>0</AGC>. With <AGC> set to 0 you must adjust your sound volume levels manually to obtain the best sound quality. Also, try toggling the automatic echo control tag, <AEC>, between 0 and 1 to see if that brings any improvementthat is, toggle back and forth between <AEC>0</AEC> and <AEC>1</AEC>.

Before making any changes to config.xml, stop Skype from running. Make the changes you want to config.xml, save your changes, and then restart Skype. Failure to follow this procedure will most likely result in your changes being ignored.


3.16.1. See Also

  • For guidance on how to edit Skype's configuration file safely, and for some additional tweaks to try, see "Tweak Skype by Editing config.xml" [Hack #45].




Skype Hacks
Skype Hacks: Tips & Tools for Cheap, Fun, Innovative Phone Service
ISBN: 0596101899
EAN: 2147483647
Year: 2005
Pages: 168

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