How Can I Remove Loud Ventilation Fan Noise

[fubar387]

How do I isolate a very loud roof fan noise from a sound track? I have tried to filter it but I cannot seem to find the right frequency. It would really help if I could see a couple of screen shots on the adjustments. This is a great little software but I am not, and I repeat not, in any way shape or form and audio person. For me terms like db’s, frequencies, wet and dry might as well be written in Klingon. I do have one advantage though, I learn very, very quickly. So if you could “teach me how to fish” rather than “give me a fish” it would be deeply appreciative. Did I mention this project was due last week….lol

I have tried to attach a small sample but it was to large to post. If you can hel;p I could send the 5 MB file via a hotmail account to you. If I make it 2 MB you don't get the vocals around the noise. To make a long story short I did manage to remove a large volume of the noise however it killed the vocals as well.

[kozikowski]

I don't know if Audacity comes in a Klingon version. I can check.

Noise reduction is designed for people that don't need it. "Noise" has to be very much lower than the conversation, or Noise Reduction will not be able to separate the voices from the noise. There's no shortage of postings wanting us to remove the noise so they can hear the show at all.

Watch your Private Messages.

Koz

[kozikowski]

Go up to the top of the forum where it says "new messages."

Koz

[fubar387]

Hi Koz,

I sent the zipped snippet to you as per your message. I appreciate you taking the time to look at it this mess. I knew it was going to be horrible when I was taping it but they could do nothing about the ventilation fans short of shutting them down and freezing everyone in the room. There are some points in the sound track where the speakers voice is at or near the frequency of the fan. When I tried using SoundBooth to wash it out it sounded like a wah wah pedal was being used. I wondered if there was a way to flatten those peaks out.

fubar387

[kozikowski]

How big was the file?
Koz

[kozikowski]

I sent the zipped snippet to you as per your message.

Actually, you didn't. You sent a Windows WinRAR file that I can't open. I could probably do it if I fired up one of the Windows® machines, but I'm out of Anthracite and the Coal Lady won't be around until Monday. Need an actual ZIP, or send the WAV file.

The text accompanying the file suggested strongly that the work was after you already tried to fix it. Don't do that. Once you mess with it, we're dead. We need as close to the raw work as possible.

Never send files with spaces in the file name. fan_noise_clip.rar. Or, in this case, fan_noise_clip.wav or fan_noise_clip.zip.

Take another shot at it? I did get the whole 6MB file in good order, it just took a while. You never said if it was OK for me to publish the work. I post it on my web site for the other elves to see it. That's how I deal with large sound files. It will be Google searchable.

Koz

[kozikowski]

That's more better. I went as far as I could go without gargling up the voice.

Before:

http://www.kozco.com/tech/audacity/clip ... e_clip.wav

After:

http://www.kozco.com/tech/audacity/clip ... _after.wav

That's it. I applied a 150 Hz high pass filter to get rid of the lion's share of the room rumble and then did an 18dB noise reduction to help suppress everything else. We're never going to create a Glen Glenn Hollywood sound track out of this. It's way too far gone with the performer buried in the room junk.

What was supposed to happen was you to put a tie-tack microphone on the performer and reduce the room noise to very low levels. We could get rid of anything you had left. You're not filtering a live performance. You're in disaster recovery.

lavalier.jpg (46.83 KiB) Viewed 5228 times

Koz

[fubar387]

A big thank you Koz.

So much better. I will try to repeat your steps on the rest of the fudged tapes.

I agree about the mics and I suggested that along with a multitude of other important things such as lighting, etc. etc. They told me "shoot as is, since we have no budget for anything else". They were aware it would not turn out as well as it could. No shit Sherlock! If my sister did not work for this important, but so underfunded NOG (Non-Governmental Agency) dealing with newcomers to Canada, in particular North Bay ON, I would have digitzed all 12 tapes, burned them to DVD and shipped them "as is" and let them deal with it. Unfortunately that kind of attitude towards what I do is not in my nature. I donate a lot of my time to my community, helping unpreviliged kids usually, so I have chaulked this job up to helping this organization out. Hey at least they paid for the camera rental and I got a few free meals out of the deal.

Life ain't it grand.

fubar387

[kozikowski]

You can get away with lighting issues very easily because your head shifts easily between television and radio. Sometimes several times in the same sentence. It doesn't work the other way. If the sound goes away, you have no show.

Noise Reduction has a couple of tricks. In any one show segment you need to capture a "Profile" which is noise-only. No dialog. Select a segment and play it to make sure you don't have anything but pure vent fan noise. It's possible to get a more accurate noise reduction by Effect > Amplify before you capture the profile. Then UNDO to put the show back to normal.

Then apply the actual reduction tool.

I should have written down the reduction numbers I used, but I'm thinking the default....

Wait. Here it is.

18dB reduction
150 Frequency Smoothing
0.15 attack.

You can keep increasing the noise reduction numbers until the voices start sounding honky and bubbly. Those were the numbers I settled on.


This is how this process is intended to work. This is a microphone I tested and as a throw-away experiment, "cured" the microphone noise with Noise Reduction.

Before:
http://www.kozco.com/tech/audacity/clips/3013Test2.wav
After:
http://www.kozco.com/tech/audacity/clips/3013Test3.wav

Listen with headphones to the spaces between words. Also note that the words themselves still have noise.
That's as good as you can do. You can't fix the noise during a word.

Koz