Noise in classroom recording

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Noise in classroom recording

Permanent link to this post Posted by Alonshow » Thu Jun 04, 2015 3:40 pm

I'm a novice teacher and I'm recording my lessons to improve my teaching technique. My recordings have a lot of noise that comes from several sources: Air conditioning, chair creaks, traffic, etc.

The method that has worked best so far has been using notch filtering when I can identify limited frequency noises and then using noise reduction. This does help, but the results are still quite poor.

My knowledge of sound editing is almost none. Anyway, after a bit of googling I've come to the conclusion that this problem is called vocal isolation. If I'm getting it right, there is no real solution for this, just some tricks that can help a bit, so I guess that's what I'm looking for.

I have checked Audacity's tutorial on Vocal Removal and Isolation, but this doesn't seem helpful for me because my recordings are mono and that tutorial talks about stereo tracks.

So, can you recommend some method, plug in or tool that can help?

I attach a sample:
Voice and noise.wav
(916.73 KiB) Downloaded 69 times


Audacity 2.1.0
Windows 7
Exe installer
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Re: Noise in classroom recording

Permanent link to this post Posted by DVDdoug » Thu Jun 04, 2015 4:16 pm

There's probably nothing more you can do. The problem is that most "natural" noises cover the same basic frequency range as the human voice. If a noise has a certain frequency pitch (like power-line hum,etc) it can usually be filtered-out. IN fact, it may help to use a high-pass filter at about 200Hz or so to filter-out any low-frequency noise.

The Noise Reduction filter can also work when you have a small-constant background noise like tape hiss, but if the noise is bad the software can't distinguish the signal from the noise and usually, "The cure is worse than the disease".

In the future, your best bet is to use a lapel mic or a podium mic for a strong signal-to-noise ratio. If that's not possible, a try directional mic as close as possible to you. You're never going to get "studio quality" in a classroom but if your voice can dominate the sounds hitting the microphone you should be able to get acceptable results.
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Re: Noise in classroom recording

Permanent link to this post Posted by kozikowski » Thu Jun 04, 2015 8:51 pm

if your voice can dominate the sounds hitting the microphone you should be able to get acceptable results.

What he said.

Image

Nobody yet has gotten good recordings from across the room or even on a chair somewhere on the stage.

People still do this for a reason.

Image

Anyway, there are a number of techniques you can use to record as long as you never need to submit to NBC, NPR or the BBC.

What are you using now before I go off in all directions?

Koz
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Re: Noise in classroom recording

Permanent link to this post Posted by kozikowski » Thu Jun 04, 2015 9:14 pm

Would this work for you (attached). I need to get the part numbers and purchase info.

Koz
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2015-06-04SoundTest.mp3
(1.79 MiB) Downloaded 55 times
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Re: Noise in classroom recording

Permanent link to this post Posted by kozikowski » Fri Jun 05, 2015 3:32 am

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Re: Noise in classroom recording

Permanent link to this post Posted by Alonshow » Fri Jun 05, 2015 5:23 pm

Thank you for the advice. I guess I already have the best I can get in this situation. It's not too bad, actually. Dealing with the noise removal process and the remaining noise is time consuming and annoying, but I'll deal with that.

Using a lapel mic wouldn't help much. These are very interactive English lessons and the voices of my students are as important as mine. For the same reason, the directional mic doesn't seem to be helpful in this situation.

Regarding the USB recorder, it looks cool, but I have a recorder already, it doesn't look like it's gonna make any improvement either.
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Re: Noise in classroom recording

Permanent link to this post Posted by kozikowski » Fri Jun 05, 2015 6:26 pm

Recording a classroom well with student interaction is a graduate course in professional sound recording. Now you know why.

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