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My Greatest Enemy (of late)
I have been doing video for quite some time now in the corporate arena. One of my biggest problems is fighting air conditioner noise. I cannot control the air because turning it off in most cases with affect an entire floor of a building and is not feasible. I do like shooting with a shotgun style mic and have recently purchased a Sennheiser MKH 416. However, the air conditioner sounds still persist. Please give me some suggestions.
I use FCP and have the studio so what are my best filters to use in order to cut the air conditioner sound?
I did post this in the audio forum but thought their might be someone here who could give me some suggestions.
Mike
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8 Replies
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I’ve never used it – but I think in Sountrack Pro there’s some module that will take a noise sample (like room tone with the air conditioner) and try and remove that noise from the audio track.
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This will occur even with the talent closely mic’d, nevermind a shotgun.
Soundtrack Pro does a pretty decent job of removing background noise. Short version:Record ambient sound prior to the interview. Do a set noise pattern, then remove noise. Works pretty well. You may have to up the bass and play with the sliders a bit.Jim
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In certain rooms a shotgun mic doesn’t help and a very close-mounted omni mic will work better. The shotgun’s directional pickup will be able to isolate wanted sound from unwanted if the two sources are essentially coming from different sides of the room. Getting the mic close to the sound source is crucial. Also, hard surfaces not only bounce the sound around in a room but they can effectively change the polar response of a mic. Example: If you point a shotgun mic down at a smooth concrete floor, you get all the sound bouncing off that floor from every direction, defeating the directional nature of the mic. If your talent is standing on the concrete floor, you’re better off holding the shotgun low and pointing it up so that it points at the talent but not at the hard floor.
So get close with a mic, then think direction, and think about how surfaces will affect the directionality of the mic.
Once recorded, you can consider noise reduction. The noise reduction filter in Soundtrack Pro works pretty well. You sample an area of your audio clip that contains the type of sound you want to get rid of. Then, you reduce that noise throughout the clip (check the help for specifics). Constant, mechanical noise like AC is not too hard to reduce with this type of filter. In your case, you would sample just the room sound, without any dialog or other sound if possible. If you get too heavy-handed with the noise reduction you will affect your desired sound source in a bad way. Try it and see if you can get get good consistent results with it.
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Is it just doing phase cancellation? That was the old school way. Record some room tone, then reverse the phase of it and mix with the recorded audio. If they’re close enough should cancel out the noise. Just like noise cancellation headphones.
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I’ve had great luck removing AC noise with SoundSoap. Works great.
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For next time, bring a few of those blue packing/moving blankets and some pony clips. Clip those over the intake and the airflow vent. While it won’t cut it out all together, it sure does help.
Jeremy
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No it’s more sophisticated than phase cancellation. Soundtrack Pro’s Noise Reduction like similar tools (e.g. Soundsoap) analyses the patterns of the sampled audio and then removes those matching patterns in the bad audio. The key thing is getting the balance right between removing the unwanted noise without affecting the stuff you want to keep.
Martin
Digital Heaven, London UK
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Yes, what Martin says is true, at least of Soundsoap. When you tell it to find the noise it tends to overdo it, making the voice remaining sound hollow, as if spoken through a tube or over the phone. You must be patient and tweak the thing to get it right. Also, I tend to do a “save as” with it and add 1 or something to the original file name, then you can save all the original clips somewhere else, remove the 1 or whatever from the new clips and reconnect the media. That way, you still have the originals should you want to change anything.
Yes, I know Soundtrack Pro can do this non-destructively, but I just like Soundsoap much better for noise reduction. Have not had as good an experience with Soundtrack.
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