Removing Room Noise

Can anyone help me out with a good procedure to eliminate room background noise from a recording? What I done so far without success is to make a 5-10 second recording of just the room. I put this on it's own track and then I flip the phase on it. I then play this back along side another track recorded in the same room. So far I haven't been able to get this to work. Am I doing something wrong? It seems a simple approach and should work.

Oh, and please no obvious responses like "move to a quiter room". I sometimes need to record in less than ideal spaces where you can't eliminate all of the background noise from things like HVAC systems.

Thanks.

If the noise is not 100% consistent (50/60 cycle hum from power lines, for example), phase-removal won't really work. You either need a quiet room, or if it's "not too bad" you can use an expander. I use an expander on just about everything... but it's in my preamp so it's convenient.

Basically, you can use Sonitus gate or search for other expanders and get similar results. If the room noise is actually audible during the performance, and not just when it's supposed to be quiet, you're going to have a very hard time with it.

Good luck!

Hello,

If only the phase thing really worked. Wouldn't it be nice if it was that simple? There are two situations: one is you have a noisy environment and the second is you have been given a piece of audio that already has the noise on it. In the first case you have the opportunity to control the noise (or decide whether or not to record in that environment). If you decide to record in a too noisy environment then you live with the consequences. If you receive a piece of audio that already is tainted, but you have not choice but to use it, then you do the best to mitigate the noise but you will not be able to remove all of it.

We're talking about "broad-band" noise (as you state, HVAC, fans, general din for instance) as opposed to impulse noise (clicks and pops). Broadband noise is called that because it occurs throughout the frequency range of the program material. The best tool I have found is Sony/Sonic Foundry's Noise Reduction plug-in (which I paid $220.00 for many years ago as a standalone product, now bundled in Sound Forge). You use this plug-in by taking a "noiseprint" of a noise only section. Then apply the plug-in to the whole clip. As don4777 says, it is best to apply this kind of plug-in 2 or 3 times with lower, less aggressive settings otherwise you can get some nasty phasing affects. Also it is best to apply the noise-reduction plug-in first, then EQ and gain work (compressing, normalizing or other), which will again bring up the noise floor, then apply the noise-reduction plug-in again at the end of processing.

After all processing, I would manually remove the noise from the white spaces with an audio editor (Wavelab is my choice).

GK

I use Sound Forge's Noise Reduction 2.0 all of the time for this type of situation and I have been able to get amazing results with it. You will need to spend some time figuring out what all of the adjustments do, but for the most part, it has been a huge lifesaver for me many times. You do have to be careful to make sure you use it wisely. For example, you can easily have it get rid of all of the sound completely, but then you might be missing some quality of the source you are trying to record. So sometimes it is good to have 10% of the noise still there so that you can have a better sound. But in any case, you are definitely looking for a plug-in like Sony's Noise Reduction 2.0, I think there is also Sound Soap and Digidesign's DINR.

I agree with others here that the reason your technique is not working is because in order to cancel out a sound, the sound waves have to be almost exactly similar and lined up so that when the phase is flipped, it cancels out the waves.

I use goldwave's sound reduction thing which is essentially the same thing as soundforge's, just a different company, so there is another option for you. I find that even a 10% reduction in noise has noticable artifacts that are similar to a low bitrate mp3, though maybe goldwave's pluggin isn't as good as soundforge's, have never compared. Just have to find a balance. I have never tried this method of using a few small reductions pre and post effects but it sounds definately worth a try. When you copy the small section of floor noise, however, make sure for the post effects reduction that you copy the noise floor from post redction, don't use the one from the original recording. I would also probably not do the second one at the very end of the effects chain, use it after things such as compression and eq, but before reverb and delays.

Noise has never been too large an issue that I have to use noise reduction, a gate is usually sufficient. Just make sure that you don't remove all the noise if there is a silent section in the song with no instruments playing as it will sound unnatural.

Only other thing I could suggest is the equipment you are using and your micing techniques. Closer micing to your source will obviously give you a higher ratio of the sound to you want to the room noise, though that obviously changes the sound of your recording. What places are you recording in? If it is in your bedroom, setting up blankets around the wall will reduce the reverb which will result in less room noise being recorded. Also be aware of noise from you computer. Make sure you are recording in 24 bit and not 16 bit. Make sure the gain on your preamp is as high as it can be safely set so no clipping occurs. The list here is obviously quite long but as for post recording, the only real options (as far as i know) are gating or using noise reduction algorithms.

Good luck!

I record live in our church.... and have to deal with Jet Airliners, HVAC systems, and so on. I found a product called SoundSoap, that works stand alone, or acts as a plug in. I recorded some "white noise" when the auditorium was empty, with and without the A/C running. I also isolated some Jet Noise from some previous recordings. This plug in has been able to eliminate the noise! It's about $80.00 on Amazon.com. It also has built in 50/60 khz filter, rumble remover, etc. I think you can go to their website and get a demo version. It did what we needed it to do, so I can't complain.

Adobe Audition also has some very good noise reduction capabilities. It allows you to sample the noise by taking a small snippet from the clip you are trying to clean up. Just a small area where there is nothing but noise. And then filter based on the specific noise found in the clip. You can adjust how aggressively you want to process the clip. If there is a lot of noise and you are extremely aggressive you are likely to get some phasing artifacts. I have had some success with very noisy clips by processing it 2 or 3 times with less aggressive reduction.

This is a great program to have in your toolkit for removing the occasional click or creak from an otherwise great recording. For live material I would hate to be without it. You can set it up using Sonar Utils (http://www.ennbr.com/SonarUtils/) to be available from the tools menu in Sonar.

+1 for this suggestion. I have used Audition with a vocal track marred by a loud computer fan and was impressed with the results. The noise was almost completely removed with no apparent harm to the vocal EQ. How well it would work for you depends on how consistent the noise is.

ORIGINAL: don4777

Adobe Audition also has some very good noise reduction capabilities. It allows you to sample the noise by taking a small snippet from the clip you are trying to clean up. Just a small area where there is nothing but noise. And then filter based on the specific noise found in the clip. You can adjust how aggressively you want to process the clip. If there is a lot of noise and you are extremely aggressive you are likely to get some phasing artifacts. I have had some success with very noisy clips by processing it 2 or 3 times with less aggressive reduction.

This is a great program to have in your toolkit for removing the occasional click or creak from an otherwise great recording. For live material I would hate to be without it. You can set it up using Sonar Utils (http://www.ennbr.com/SonarUtils/) to be available from the tools menu in Sonar.

Good luck.

Don

FYI - SoundSoap works in an identical fashion.