removing echo – noise gate? what does it all mean.

[Dennis Leppell]

Instead of fixing it in post, in the future you should fix the problem at the source.

Sound waves are like rubber balls. They like to bounce around. The wooden panels on your walls is giving them a really nice service to bounce off, and then picked up by your microphones. The more uninterrupted the surfaces that are available for the soundwaves to reflect off, the more pronounced the effect. An empty rectangular room with hard floor will echo horribly, but if you fill it with carpet, furniture, drapes, etc, the echo dies.

To fix your issue, hanging foam padding, drapes, or even sheets or blankets to absorb these stray soundwaves will have great results on your future sound recordings.

[Mike Johnson]

I had the same problem on a project a couple of months ago. The camera op didn’t use headphones to check the audio and there was a bad echo. Come to find out he didn’t have the audio input set right on the camera and it was taking the signal from the onboard mic rather than the lav. After fiddling with the audio for about a day in both FCP and STP we finally got it fixed. We reshot the interview. If the echo is subtle, you can try to cover it up with a music bed. Otherwise there’s not much that can be done.

Mike Johnson

Final Cut Pro Editor

Drury Outdoors

http://www.druryoutdoors.com

[John Fishback]

If it really is echo, you can’t remove it. However, it sounds like some phase cancellation may be happening. That’s where sound from talent reaches the mic at a slightly different time than a wall reflection and that can create that hollow sound. Frequencies from 150 to 400 Hz are the range to play around with. Try cutting and boosting in this region and see what happens. Use a parametric eq.

John

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[William Hughey]

If you can not hang acustic dampning material (egg crate, sheets ,carpet) on the walls you might want to try sampling the talent, and feeding a small ammount of audio back into the room 180 degrees out of phase. This will cancell some of the echo or some of the audio frequencies. This will depend on the room size and placement of the monitor speaker. Audio delay is also a nice thing to have on hand when “trying” to cancel echo or acoustic echo in a room electronically instead of mechanically.
Sample the audio either from the mic or second mic, delay the audio just a bit (a few ms, 65 ms is good by routing the mic through an adjustable audio delay board) then to a amp and monitor speaker (placement in the room will have the greatest effect) invert the phase of the sampled audio (switch the polarity of the speaker around not great but effective on a budget) adjust the delay, audio level, and placement of speaker for best effect.
This is not easy it is not an exact science you can try it with out spending thousands of dollars on computer programs and equipment. The best way to stop acoustic echo in a room is with sound absorbing material or sound dampening material, Foam packing material that resembles a egg container with peeks and valleys will work as well as the expensive stuff made for the studio. If you cannot hang something on the walls try the phase echo cancellation experiment.