Help with removing background noise? Frequency filter?

W

wmiller@csulb.edu

Well-known member
I was wondering if anyone knew how to remove a computer humming noise in the background from some audio?

I did a search but found nothing about this topic. I think you can do this with some sort of frequency filter to single out the frequency of the computer humming (fan) type noise?

The clip is from inside a radio studio, and i was recording sudio from the studio mic, as well as a boom i had placed over the actor. The humming noise is coming from all the computers that are in that room, and the boom picks all of that up, faintly, but nonetheless it is distracting. I need to use some of that audio track and if anyone could help me take this noise out, i would really appreciate it. (i am on FCP5)
 
A noise removal plug-in would be the simpliest solution but realize that it is likely that the computer noise is on the same frequency as your voices. You can dial it down to find a compremise between voice quality and BG noise.

If you don't have a noise removal plug-in you can do a frequency sweep with a parametric equalizer until you find the frequencies that are the worse (fan noise is usually a broadband noise) and pull those down freq down. Again looking for a voice to noise compremise.

Good luck
 
I know nothing of Premeire but since it is a video editor I doubt it has much audio sweetening capabilities. Adobe also makes Audition which is actually a really nice audio app and from what I am told has a really nice integrated workflow with Premiere. I would consider getting Audition if I were you.

Good luck
 
For ease of use, it's hard to beat Soundsoap.

http://www.bias-inc.com/products/soundsoap/

You can dial in the amount of noise that is reduced and keep previewing what it will sound like. If you remove too much, it can sometimes make dialoque a little "tinny". But it is the quickest way to clean up tracks that need it.
 
Well, there is another way to remove the background noise that no one mentioned - ADR. ;-)

Seriously, this is why it gets so frustrating to see all these people come into this forum, assume they can buy a mic (whether it's an ME66 or a 416 or a CS3E) and get great sound. More important than the microphone (and yes, this has been said before) is listening. WMiller, I'm not knocking you specifically, but, let me ask - did your sound mixer/recordist note the computer noise in their logs? Did they hear it? Was it brought to your attention and your first thought was "we can fix it in post"? (BTW, if so, then I am knocking and mocking you....).

A good, reasonably experienced mixer would have heard this, and done something about it - well, made sure the appropriate department did something about it (it is rare that you can't shut a computer off during a take, or in some other way dampen it to cut the noise - a sound blanket over a computer for a few minutes will not hurt it).

I recently mixed a scene where I was hearing a loud clicking noise. I requested a hold from the director, and my microphone started scoping out the scene (my presumption was it was a loud watch or clock that we had missed). Turned out the source was an artificial valve in one of the actor's heart. And, we re-positioned him away from the main dialogue (the director did this after I reported the problem) and I re-positioned the microphone slightly off axis and we got the scene without a problem. But, that is because the first thing I did was listen.

(Oh yeah, and back to the computer...I had one director insist that the computer screen had to be in the shot with a particular picture on it...in a very friendly way, I told the director about another project I was on where they used chroma green gaffer tape on the screen and stripped the image in in post...and that's what we did. You can deal with computer noise problems in many creative ways...actually you can deal with almost all noise problems in many creative ways. And one final rant before I jump down off my soapbox - This is why you take your mixer on location scouts. They will hear and notice sound problems that others on the crew will miss. The gaffer will be all over the circuit breakers, so why not bring sound in to tell you that you need to find out in an office how to turn off the air conditioning so you don't get that annoying hum in all your shots.)

Okay, I'm off my soap box now.

Phil
 
There maybe be another option. Find a piece of audio from the scene your talking about, where there is no talking, or extra noises other than the noise you've mentioned....depending on how much room noise is also in there, you can do a hum detection, white noise detection, pink noise detection...and when you figure out the frequencies, you can notch it out with an eq. in an external audio program. I had to do this once for a movie i was working on. Turned out ok. I exported the wav file again, and resynced it with the movie in the timeline.
I've been a Magix Audio Studio user for years, before I was into video, and I still use it for things like compression, DC removal, noise removal...etc..

Next time take preventative measures...
1. Before setup, take a room noise sample.
2. After setup, clear the room and take a noise sample.
3. Between takes, actively listen for things you would hate to hear in post.
 
Phil,

I agree 100% with the rant. Being in post I'm the one who ends up dealing with the crappy audio. However being as this one is in the can and it too late to do the things that would have mitigated it in the first place... ADR is not the first choice. It is expensive and time consuming to do right and looks horrible when done wrong. Sound Soap may work for this, but you are probably going to get better results with a harmonic filter. SS works pretty well on broadband noise but hums are not really broad band noise. There is a plugin, now marketed by Roger Nichols, but created by Elemental Audio that has a very good harmonic filter. Also there is an old hardware box (Roland SN-550) that has a harmonic filter. Use light passes and after each one compare with the original and ask the big question... Better or just Different. You will probably not be able to get rid of the noise but you might be able to make it a lot less noticeable. It is very easy to over do broadband NR so go light or it will end up sounding worse than when you started. If that doesn't work then it's ADR time.
 
SoundSoap is crap. I have it, and it has never really worked well at all. I use it more as a sound design plug in these days as it does a good job of flanging.

Here are some things to consider:

Is the computer noise natural?
- If the scene lends itself to having that in the BG anyway...then who cares?

Is the computer noise louder than the dialogue?
- If not, then just leave it alone. People are always concerned about what's going on in the BG audio during a shoot. If it sounds natural, then don't worry about it. The only time it becomes and issue is when you have an inexperienced sound mixer and they don't deal with different angles well, but I can usually smooth that out.

-Dave
 
Dave,
I would have to disagree. It's not NONOISE but its not $5K either. Sort of like BNR you have to use a light hand. It works OK for some things and actually if you just use the pop filter it can do some decent salvage work on digital distortion, about the only thing I have seen that does much for that. It's a tool use it for what it works well on and you can get decent results, use it on things it doesn't work well on and it's...crap. Computer noise is a candidate for the kind of noise it won't do to well on. But that is also true of pretty much all broadband noise reducers. It's too periodically peaky and you will tend to get comb filtering (phasing/ flanging). Steady state noise like some Air conditioning, tape hiss, etc it will usually do pretty well on.

Dave_Fisk said:
SoundSoap is crap. I have it, and it has never really worked well at all. I use it more as a sound design plug in these days as it does a good job of flanging.

-Dave
Click to expand...
 
Hey there.

I edit with Premier and use Adobe Audition "Noise Reduction" plugin to get rid of all my background noise. Works like a charm. Air conditioners, fans, florescent lighting buzz, you name it.

I think there's an evaluation version out there. Let me know if you want to try it out.

PR
 
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