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Old October 12th, 2010, 09:56 AM   #1
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Need some help removing slight annoying feedback ring

I recently shot a business seminar where I was in charge of providing and managing both the PA sound for the speakers as well as the video. All sound was run through a Soundcraft mixer board that I rented. Throughout the speaking presentations, I have a slight annoying feedback ring that I would like to try and remove. I am post producing with FCP. Any idea on which audio filters I should try to do this with?

TIA for any advice! I could post a small audio sample if necessary.
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Old October 12th, 2010, 10:34 AM   #2
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Two words: "Parametric EQ"
'Zero in' on the offending feedback frequency with a 'notch filter', set the bandwidth as narrow as possible to do the job.
A noise reduction plug-in could also be utilized but is usually not necessary.
By all means, post a sample.
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Old October 12th, 2010, 10:49 AM   #3
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Thanks for the reply! Here is a sample representing probably what is as bad as it gets throughout the presentation. I was monitoring via headphones and adjusting throughout the presentation live so it's not terribly bad in most all the rest of the presentation, but it would be nice to get rid of this annoyance in post. It is however slight present in all of the presentation. TIA!
Attached Files
File Type: mov Feedback Ringing Sample.mov (14.11 MB, 95 views)
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Old October 12th, 2010, 10:53 AM   #4
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Please disregard that first sample and use this one instead. There were some filters already on it I realized when I exported. This one is the raw recording.
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File Type: mov Feedback Ringing Sample 2.mov (16.00 MB, 110 views)
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Old October 12th, 2010, 12:42 PM   #5
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Dennis, the QT file will not open on any of my PCs, XP, Vista, & Win7. (latest ver.QT-7.6.8 .
In addition the download hangs for a few minutes at about 15.9MB of the 16.14 file.
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Old October 12th, 2010, 12:50 PM   #6
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Ah, ok, let me re-export using QT conversion... that was straight off the timeline... Here, give this a go...
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File Type: mov Feedback Ringing Sample 3.mov (16.00 MB, 75 views)
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Old October 12th, 2010, 01:43 PM   #7
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If you have access to Adobe Soundbooth or another editing program that allows direct visual editing on the spectrum display, the ringing is easy to spot, select it and delete. For consistency, it would be good to delete that narrow strip from the whole take, as it affects the sound of the voice to a small extent. I am attaching pre and post spectra and pre and post .wav files of the small sample I did this with...see if you like the result...

In the post-cut wav, you will hear the small band of unaltered audio, followed by the altered audio, then ending with the unaltered clip, just as you see in the spectrum where the ringing was removed...the difference in the reverb, even with no feedback ringing, is why you might like to remove that small part of the spectrum for the full clip...just for consistency...
Attached Thumbnails
Need some help removing slight annoying feedback ring-postcut.jpg   Need some help removing slight annoying feedback ring-precut.jpg  

Attached Files
File Type: wav precut.wav (5.52 MB, 58 views)
File Type: wav postcut.wav (6.69 MB, 53 views)
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Old October 12th, 2010, 02:02 PM   #8
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Hi Dennis, I can render the feedback pretty much inaudible, without affecting the speaker's voice very much by notching out the offending frequencies on an aforementioned Parametric EQ with the below settings:
Center frequency: 568Hz.
Bandwidth: 0.3 (octave)
Attenuation: -25dB
Make-up gain: around 2dB.

I was also able to accomplish this with a Noise Reduction plug-in, (Sony/SCS NR-2) but it took more time and additional tweaking of the captured noise-print to eliminate artifacts.
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Old October 12th, 2010, 02:08 PM   #9
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Yes, I do have Adobe Soundbooth and I also have Apple Soundtrack Pro (comes with FCP Studio). I just tried this with my sample using your suggestions in Soundbooth and yes, this is acceptable. This is exactly what I am looking to do... when removing this frequency, it kind of makes the voice sound a little like it's in a tunnel, but I think I can perhaps use another filter to fix that... as always, a little experimentation goes a long way but this helps immensely! Thanks so much for pointing me in this direction!
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Old October 12th, 2010, 02:09 PM   #10
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Thanks for your input as well Rick! I'll give your suggestions a try using the Parametric EQ with your settings and see where I land. Very much appreciated!
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Old October 12th, 2010, 03:27 PM   #11
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Similar idea in Izotope - just attenuate that narrow band and it works. I played around with moderate attenuation in the center of the band and then a lighter attenuation in a slightly wider band centered at the same frequency and got a pretty nice result without "tunnelizing" the voice. Lots of ways to skin this particular cat!
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Old October 12th, 2010, 03:39 PM   #12
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Thanks for your input as well Jim! I have proven once again, that while I am primarily a videographer, it is the audio I am spending the time on perfecting for my client! Two cams on this shoot so a touch of color correction and we're good to go!
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