Isolating a frequency in post

Jim Brennan

Jim Brennan

VHS Member Old Skool
I was recently on a shoot where, on a few of the takes, I heard a high pitched sound, almost like my ears were ringing. I mentioned it to the director and the rest of the crew, some of whom could not hear it at all. We could not figure out what it was (or it was my imagination), so we shot. Naturally, it showed up on some of the takes the director wants to use. How do i isolate it? It is far above the frequency of the human voice, so I am hopeful there is something I can do.

Thanks in advance.

Jim
 
Pro Tools has a plug in that basically lets you dial through all the different frequencies to isolate the one you want to eliminate. It's been a few years since I used PT, so I don't even remember what it's called. Not sure if that's a standard feature on any other audio programs, but somebody must have a plug in for whatever you're using. Sorry I couldn't help more- but congratulations on the super-human hearing!
 
semila58 said:
Sorry I couldn't help more- but congratulations on the super-human hearing!
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Yeah, for all the good it did me :beer:

I just use soundtrack and FCP, although I think I have an old version of Cubase somewhere. I'm not really an audio guy most of the time. I'm just trying to help him out. Thanks though :thumbsup:
 
Jim, I would think some sort of Spectrum Analyzer plug-in would work. That way you could see the peaks from the different frequencies...

Either that or just bump down the levels per frequency band until the noise goes away... :)
 
semila58 said:
Pro Tools has a plug in that basically lets you dial through all the different frequencies to isolate the one you want to eliminate. It's been a few years since I used PT, so I don't even remember what it's called. Not sure if that's a standard feature on any other audio programs, but somebody must have a plug in for whatever you're using. Sorry I couldn't help more- but congratulations on the super-human hearing!
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It's called: Equalizer :)

Take any eq, and dial in a single band with a narrow q. Then boost the band to the max and sweep it across the entire spectrum until the noise pops out. Then, just cut that frequency and adjust q to taste. It works even better if you loop a small 'room tone' section that just contains the offending noise and not a bunch of other stuff.
 
I would think a sweepable sine wave oscilator would help you match the pitch and then you could reverse the phase to cancel the wave. If it works then simply match the pitch where ever it occurs on a seperate track and reverse the phase. You might have to slide the sample around a bit to nullify the offending tone.
 
tigeba's right.

To elaborate a little further on what he said, use a peak (not shelf) EQ set to a narrow Q (bandwidth), set it to a high level of boost and sweep its frequency across the spectrum until the noise is most exaggerated. Be careful with monitor levels as you do this, as the offending frequency could get quite loud.

Once you've found the frequency (Kenneth!), fine tune it by narrowing the Q even further and sweeping the frequency in minimum steps until the noise is most accurately spotted. Then, without changing the Q, fully attenuate the EQ band. If the noise disappears, try less cut until you hear it again, then back down again until it's gone, but no more. This way you the minimize side effects.

If it's still there after the initial attenuation setting, then try widening the Q until it's gone. If that doesn't quite fix it, or if there is too much unwanted effect on the overall sound, try adding in a second (or third, or fourth) band set to the same frequency to increase the attenuation. If it's available, Waves Q10 is an excellent EQ for this application, but most parametric style EQs (adjustable boost/cut, frequency, and bandwidth) will do a good job too.

Noise reduction plugins such as Digidesign's DINR can also work, but generally for an isolated frequency noise like this a "surgical" EQ as described above (and by tigeba) is most effective.
 
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Frequency sweep with a parametric eq is the standard. I saw a demo on Soundtrack Pro where you can cut out offending frequency under the specral view.

I don't use Soundtrack so I haven't tried it but it might be worth a test since you are using that program. The demo was on the Apple's Soundtrack Pro website. Check it out.

Cheers
 
tigeba said:
It's called: Equalizer :)

Take any eq, and dial in a single band with a narrow q. Then boost the band to the max and sweep it across the entire spectrum until the noise pops out. Then, just cut that frequency and adjust q to taste. It works even better if you loop a small 'room tone' section that just contains the offending noise and not a bunch of other stuff.
Click to expand...

Yep!
 
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