TeamApart Blog

Flash-based audio conferencing solutions have always had that annoying echo you sometimes hear after talking through your microphone. You’ll notice the echo when the person you’re talking to is using speakers. Your voice (coming from their speakers) is picked up by their microphone and is then sent back to you. Flash has an “Echo Suppression” setting you can toggle on (right-click on a flash app and go to settings) but it doesn’t help much as it merely reduces microphone gain. There is a feature request for Acoustic Echo Cancellation in Flash 10, but no word yet of whether it’s approved or not.

In the current version of Flash, you have a couple of options to get rid of echo. First, you can make sure everyone in the conference with an active microphone is using headphones. It seems like most sites rely on this method by displaying a “We recommend wearing headphones” message, like Tokbox. Second, you can have a push-to-talk feature where the user has to press a button to say something. This reduces the chance of their microphone being on while sound is coming out of their speakers.

We dislike both of these solutions because they add complications for the user. Instead, we decided to let the user modify their own “silence level” which is basically the amount of sound required to activate their microphone. When the active sound level is greater than the silence level, the microphone begins transmitting the sound until the sound level is below the silence level for more than two seconds. The goal is to set the silence level just high enough so the sound coming out of the speakers won’t trigger the microphone to begin sending.

The tricky part in implementing this feature is how to make it easy and intuitive enough for the user in the UI (which is usually the case with most of our features). We chose to add another thumb to the microphone volume slider on the right hand side of your webcam display which you can use to modify the silence level. When your microphone is not transmitting (the microphone meter is below the silence level thumb) you’ll notice there is a red bar below the silence level thumb. However, when the microphone meter reaches above the silence level thumb, the red bar disappears and the microphone begins transmitting.

Hopefully this feature will help reduce echo with people using speakers in Meetcast conferences. Also, cross your fingers for Acoustic Echo Cancellation in Flash 10! If you have any other solutions for reducing echo in conferences, we’d love to hear!