How to remove echo from recording?

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How to remove echo from recording?

Permanent link to this post Posted by rain-13 » Mon Oct 29, 2012 7:50 pm

Hello

My recording has echo because microphone caprutes both: speaker's normal voice and amplified voice that comes out of loud speakers. The echo has about 0.1 sec (100 ms) delay from original.

Also. Is there way to mute sounds that are below x db and above y ?
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Re: How to remove echo from recording?

Permanent link to this post Posted by steve » Mon Oct 29, 2012 7:58 pm

There's only one cure that really works and that is to re-record (use headphones not speakers for monitoring)
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Re: How to remove echo from recording?

Permanent link to this post Posted by rain-13 » Mon Oct 29, 2012 9:13 pm

There's nothing I can do about loud speakers. The speaker (person who gives a speech or lecture) uses loud speakers (an electromechanical device which produces sound) to amplify his voice in auditorium because otherwise those who sit back wouldn't hear him.

I did not use speakers to monitor.
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Re: How to remove echo from recording?

Permanent link to this post Posted by kozikowski » Mon Oct 29, 2012 10:09 pm

Those are all frequently asked questions. They are also guaranteed ways to kill your show. You quality for 1 and 4.

-- The Four Horsemen of Audio Recording (reliable, time-tested ways to kill your show)
-- 1. Echoes and room reverberation (Don't record the show in your mom's kitchen.)
-- 2. Overload and Clipping (Sound that's too loud is permanently trashed.)
-- 3. Compression Damage (Never do production in MP3.)
-- 4. Background Sound (Don't leave the TV on in the next room.)

We would have no trouble removing one simple, perfect echo, but they're not simple and they're never perfect. Echoes are the speaker's voice arriving at the microphone more than once offset by time. So right away, we're telling to software to remove the performer from himself. Everything in the room affects the quality of the echo and makes it less and less likely that anybody's going to be able to help.

Oddly, this same problem occurs at the other end of the chain. "Put a good echo into this voice." Those always sound fake because real echoes are insanely complex and you can't generate insanity with normal computers.

Not easy this echo thing.

The other question, the lower than a certain level thing is doable. There's a tool for that called a gate that only opens when the sound goes over a certain volume.

viewtopic.php?f=39&t=30996
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Re: How to remove echo from recording?

Permanent link to this post Posted by steve » Tue Oct 30, 2012 12:09 am

rain-13 wrote:There's nothing I can do about loud speakers. The speaker (person who gives a speech or lecture) uses loud speakers (an electromechanical device which produces sound) to amplify his voice in auditorium because otherwise those who sit back wouldn't hear him.

Then the next best thing is to use a microphone as close as possible to the person's mouth.

A high quality headset mic would be ideal.
Here is an example of a (professional quality) headset mic that is discrete, not too uncomfortable, and capable of excellent sound for the both the sound reinforcement system (the loudspeakers) and the recording: http://www.dpamicrophones.com/en/mic-gu ... item=24053
(note that the "reverberation" on the voice in that sound sample has been added after recording so as to make the vocal sound more "spacious" - the direct sound would be a lot more "dry" sounding.)

Are you able to record directly from the sound reinforcement system? What sort of microphone is used for that?
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Re: How to remove echo from recording?

Permanent link to this post Posted by rain-13 » Tue Oct 30, 2012 12:58 pm

Are you able to record directly from the sound reinforcement system? What sort of microphone is used for that?

Nope :S I am student who wants to listen teacher's speech again at home. So they wont give me access to they're sound system.

In my recording echo is almost perfect and has always constant delay which is very small which made me think i could clean it.
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Re: How to remove echo from recording?

Permanent link to this post Posted by steve » Tue Oct 30, 2012 2:11 pm

"Almost perfect" is not close enough to be able to "cancel out" the echo.
The best that you will be able to do is to use a "Gate" to cut off or reduce the level of the sound when it drops to a set level. This will not reduce the echo that is superimposed over the direct speech, but can reduce the echo that is after the direct speech.

Probably the easiest way to do this is with the Noise Removal effect: http://manual.audacityteam.org/o/man/noise_removal.html
Use the Normalize effect first and normalize to -1 dB. http://manual.audacityteam.org/o/man/normalize.html
Then with the Noise Removal effect:
Get a Noise profile using a typical 10 second section of the lecturer talking.
Apply the noise reduction with "Amount" set high (try maximum) and the Sensitivity set to minimum (try frequency smoothing set to 300).
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