Audacity - Recording of Lecture in echo-y room - How to get rid of echo.

brothertruffle880
brothertruffle880 used Ask the Experts™
on
I made a voice recording (a speech) in a echo-filled room.
How can I use audacity to get rid of the echo in the recording?
Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
Dr. KlahnPrincipal Software Engineer

Commented:
In theory, this could be done if a stringent set of constraints is applied beforehand.  You would need to go to the room, quiet it, use an audio pulse generator and measure the frequency response, amplitude, phase correction and delay time of each individual echo in the room.  Then at the speech, mike up the speaker as close as possible.  Do not let the speaker talk any longer than the time of the first echo return so that there is no overlap between the speaker and the echoes (Clearly, that is impractical, and anyway, if it were done the echoes could just be clipped out.)

Later on, process the recording by:

for each individual echo do:
  delaying the speaker's speech the required time
  frequency correct the signal
  phase correct the signal
  amplitude correct the signal
  subtract this signal from the main
until done

It's pretty obvious that this is not at all practical.  The only way to effectively eliminate echoes is to mike up the speaker properly so that echoes are reduced as much as possible in the original recording.  With a recording that is full of echoes, all that can be done is live with it.
David FavorFractional CTO
Distinguished Expert 2018

Commented:
Tough to remove echo with any type of software.

Tip: Won't help this time + next time, place a cheap digital recorder on the podium next to the presenter.
Michael ElliottHelpDesk Technician

Commented:
Hi Brothertruffle,

Audacity has the ability to remove noise below a certain volume via noise profiles and noise removals, I've used this to remove white noise or other ambient sounds or weird glitches.

You can find the details here: https://theaudacitytopodcast.com/tap012-how-to-remove-noise-with-audacity/ (you may have to scroll down to the "Removing noise after you have recorded" section)

Here are the steps you'll want to do to utilize this:
1. Select the sections of your audio that are just noise and echoes, after you are done actually speaking.
2. Go to the Effects menu and click 'Noise Removal'
3. Click 'Get Noise Profile'
4. Select all of the audio from which you want that background noise removed, which would probably be your entire lecture.
5. Go to the Effects menu and click 'Noise Removal' once more.
6. This step is optional, and allows you to fine tune the removal. Here you can adjust the settings if necessary.
7. Click 'OK'

Please be aware that if the sound that you selected from your noise profile is too close to the intended recorded audio, such as if the echoes are very loud and clear, you may end up messing with the audio that you actually want. Be sure to listen to your recording to ensure that it doesn't sound muffle or underwater.

Regards,
Exploring SQL Server 2016: Fundamentals

Learn the fundamentals of Microsoft SQL Server, a relational database management system that stores and retrieves data when requested by other software applications.

Author

Commented:
Hi Michael:
The noise removal feature does not clean up an echo-y room recording.
Completely removing these effects from a recording is impossible but you can adjust it somewhat in Audacity with a plugin called Noise Gate
Installs to the list of Effects in Audacity.
This is an old tool. But if used correctly may work.
https://sourceforge.net/projects/noisegator/
Steps
Open the audio file with the echo you wish to reduce in Audacity. Click "Effect" on the toolbar and select "Noise Gate" from the list. The noise gate window is an offline effect, meaning that it will process your audio before you play it back to hear the effect.

Set the controls of noise gate to remove echo and other unwanted noise content.
Start with "Level reduction" at -100, "Gate threshold" at 30 and "Attack/Decay" at 75.
Level reduction tells the gate how much to reduce unwanted audio.
The gate threshold sets the volume level at which the gate starts to reduce sounds and the attack and decay setting affects how quickly the gate process starts and stops. Click "OK" to start the process.
Use copies of your audio file.

Newer try Wiki Steps using Noise reduction.
https://www.wikihow.com/Remove-Echo-from-Audio
When a recording includes echo and only one mic was used to record it, this is nearly impossible to split out the noisy track and keep a separate main Track.
Regards Merete

Author

Commented:
Thanks Merete!
Hello brothertruffle880. Hope you are well.
Happy I could help you.
Really the best solution is to move the microphone closer to the speaker.
All the best

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial