Notching out high-frequency ring from CRT video monitor

overnighttolondon

overnighttolondon

Well-known member
This seems like more of a production audio forum than post-production, but maybe someone can help me out (don't think it's too tough a problem).

I have a high-pitched tone on my audio track that (as far as I can tell) was coming from my on-set CRT video field monitor being too close to the scene (you know that TV-on noise...)

Two questions:
(1) Is that likely to be a pretty pure frequency that I can notch out?
(2) What software (or VST plugs) would you recommend for monitoring multiple frequencies (like seeing my on-the-fly levels in an EQ-style display so I can isolate the frequency), and what software should I use to perform the notching after I've isolated it (will Adobe Premiere Pro 2.0 do the trick or should I be sticking to something like Audition or Sound Forge).
 
You should be able to use a plain old equalizer. My suggestion, set the Q so that it is fairly narrow, and crank up the gain all the way. Sweep the band back and forth until you hear the tone emphasized. You have now identified the frequency of the whine. Now just turn down the gain on that frequency. As long as you keep it fairly narrow it will hopefully not impact your sound greatly. If you are lucky there won't be much audio information in that region anyway.
 
tigeba's advice should be able to work well, but it could be useful to have a visual representation of the frequency spectrum so you can pinpoint where the unwanted tone is before EQing.

I dont know any free EQ plugins that do this, there are several good payware ones but I guess you wouldn't want to buy one just for this, plus there are bound to be many capable freeware plugins around.

http://www.kvraudio.com/get/1663.html - I think thats a free VST spectrum analyser, wont let you EQ - just get an idea of where the problem frequency is
 
Thanks a lot guys - for some reason I haven't had much luck isolating it with that EQ method, but I'll play some more. I'm starting to worry that it's not a pure frequency but instead just high-frequency noise (which would make some sense based on the thing making the sound).

That spectrum analyser looks great, I can't connect to their site right now though. I'll try again later.
 
Got it!

Ok, so after a little more poking around in Sound Forge, I discovered the built-in spectrum analysis (oops!), which is quite good.

Problem frequency was at 15,742 and all I needed was 0.1 octaves to notch it out completely, so I should be just fine in terms of preserving other audio. I guess its precise and slim profile explains why I had so much trouble just scanning my EQ across looking for it.

Thanks for the help guys
 
Last edited:
THe plug in of choice for this kind of job is from Elemental Audio. THey make a pair of EQ plugs that are great and one has a harmonic filter. You probably have higher harmonics with that tone but most are above hearing so it probably doesn't matter, but with lower pitched buzzes and hums the harmonics are a killer.
And the plugs are very low cost and they have very useful free demos.
SK
 
You must log in or register to reply here.
Back
Top