Echo Cancellation

This page is under revision to reflect the status of Echo Cancellation in June 2011

Echo cancellation: Audio systems, such as included in a PC, that involve a microphone and speakers may cause the microphone to pick up the audio from the speakers and send it back to the originator; this annoying and distractive behavior is called “echo”. When using a PC this issue was originally addressed by requiring a headset where the “speakers” are directly attached to the head in a way such that the headset’s microphone does not pick up the conversation coming out of the speakers. Skype has not only developed “echo cancellation” techniques that eliminate the need for a headset or phone handset to avoid this echo but also taken measures to reduce background noise. More ….

 

Audio systems, such as included in a PC, that involve a microphone and speakers may cause the microphone to pick up the audio from the speakers and send it back to the originator; this annoying and distractive behavior is called “echo”. When using a PC this issue was originally addressed by requiring a headset where the “speakers” are directly attached to the ear in a way such that the headset’s microphone does not pick up the conversation coming out of the speakers. Skype has not only developed “echo cancellation” techniques that eliminate the need for a headset or phone handset to avoid this echo but also taken measures to reduce background noise.

But ideally one would like to simply use the microphone and speakers built into a PC for (Skype) voice conversations. As a result Skype has developed a voice engine that is not only provides high quality HD Voice but also includes “echo cancellation” algorithms such that what comes out of a PC’s speaker does not come back through the PC’s microphone. In the spring of 2007, Skype introduced a version that incorporated echo cancellation; the initial experience is described in this review: Skype 3.2 Sets New Standard for Voice Quality. Associated with echo cancellation are algorithms for background noise reduction that provide clearer conversations in a noisy environment such as encountered in an exhibit hall.

2 Responses to Echo Cancellation

  1. Louise Vail April 15, 2009 at 10:06 am #

    I do not like Version 4 and have deep difficulty using it because of (a) echo (b) not hearing my caller most times (c) a loud crackling noise which we cannot trace or eradicate(sound tests for both parties are perfect).It is too quiet on full volume. and I can only hear it if I am sitting at the computer.

    Can I please download Version 3.2, I try but it keeps reverting to useless, troublesome Version 4. I need assistance here please.

  2. Jim Courtney April 15, 2009 at 10:29 am #

    Louise, I have passed along your comment to a contact at Skype for follow up. But do make sure you have upgraded to Skype 4.0.0.224 for Windows – several bugs were fixed in this hotfix version.

    Echo cancellation can be affected by your particular hardware configuration, especially the sound card. (One benefit of Macs here is that Apple totally controls the hardware and its quality and has excellent echo cancellation performance on Skype for Mac 2.8 beta or later as a result.)

    On a Windows PC ensure that Skype is detecting the appropriate mic and speakers by going to the little drop down arrow, called "Other call functions" when you run your cursor over it, at the right of the Call bar – just to the right of the volume control in the Call bar. Select "Sound Settings" and check that Skype is detecting your proper hardware. Windows can have a tendency to arbitrarily change a PC's sound hardware selection.

    The other source of your problem could be your sound card; they are of variable quality overall. (USB headsets usually include their own internal sound card which overrides the PC's and gives the headset manufacturer control over sound quality.)

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