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Subject:Spectrum Analysis
Posted by: blackrm
Date:11/9/2004 11:48:23 AM

Hello.

I'm somewhat new to Sound Forge and have a question concerning Spectrum Analysis. I know you can see the frequencies of someone speaking, but how would it (or can it) help remove coughs, etc. from audio? Any suggestions on removing these noises would be appreciated.

Bob

Subject:RE: Spectrum Analysis
Reply by: Geoff_Wood
Date:11/9/2004 1:00:56 PM

The simplest way it to 'select' the cough area on the timeline, and mute the section(s). To be a little more sophisticated use a volume envelope.

geoff

Subject:RE: Spectrum Analysis
Reply by: blackrm
Date:11/10/2004 8:52:03 AM

Thank you. What if the cough is on top of spoken words? Can spectrum analysis (from another area of the wav file) give an idea of what frequencies could be eliminated - thereby eliminating the cough (although it's probably not that easy when all is said and done).
(I'm trying also to figure out what I should use the spectrum analysis for.)


Subject:RE: Spectrum Analysis
Reply by: Rednroll
Date:11/10/2004 12:27:05 PM

This is precisely a good way to use the Spectral Analyzer. More useful would be a "Peak Hold" function for doing what you are trying to accomplish, since you said the cough is over some other speaking material, therefore it's most likely louder than the material laying behind it. The Sound Forge Spectral Analyzer doesn't have a true "peak hold" function, but here's what you can do to achieve similar results. In SA, set the "Hold Peak Value" duration for 60 Seconds. Select an area of the audio surrounding the cough noise, make sure the selected area is less than 60 seconds. Put Sound Forge in Loop playback mode. Put the SA in Live "monitor output" mode. Now Playback the audio, and look at the chicken scratch dots, which are the "peak hold" spectral curve. Take notice of the spectral curve when the cough is not present. Then when the cough happens, look at the large peak the cough makes in the SA. Try to take a snapshot of the SA when the cough occurs. Make note of the middle frequency of this cough. Place an EQ in the plugin Chainer with a Knotch filter. Set the center frequency of the EQ to the center frequency of the cough noise. Reduce the gain by -10dB to start. Play the audio back and look at how much the Knotch EQ has reduced the cough sound. If it effects too much frequencies outside of the cough noise, then increase the Q, or reduce the bandwidth...depending on which EQ you use. Try to make the Q as narrow as possible to avoid the EQ removing other parts outside of the frequency of the cough. Once you get a good Q setting then start adjusting the gain reduction amount, to what sounds best, where it minimally effects the surrounding audio.

Subject:RE: Spectrum Analysis
Reply by: rraud
Date:11/11/2004 10:29:39 AM

Another way to eliminate a cough is:
Highlight the cough, Select- Tools> Repair> Replace. Depending on the program material this may-or-may-not work.
If it's a spoken word program .. AND the cough occurs during a pause, you can just delete it, or copy a space or pause with no talking or un-disirable noises, (aka; room-tone) Highlight the cough, Right-click and select "Overwrite".

Subject:RE: Spectrum Analysis
Reply by: blackrm
Date:11/11/2004 9:05:23 PM

Thank you for a detailed and informative answer. The best thing is, I think I understand it and can put the spectrum analyzer to use working on eliminating coughs and other noises. Thank you for taking your time to explain what to do so well.

Subject:RE: Spectrum Analysis
Reply by: blackrm
Date:11/11/2004 9:10:52 PM

Hello. Thank you for replying to my question. I will try using your method to eliminate coughs also, but rednroll sure gave me the complete rundown on using the spectrum analysis tool to do so. Thank you all for your help.

Subject:RE: Spectrum Analysis
Reply by: dpalmer
Date:11/12/2004 9:08:36 AM

Adobe Audition 1.5 has a feature called "Repair Transients" under the Favorites menu. I've been quited surprised at the results of removing noises, like coughs, bumps, and otherwise short impulses that "don't belong" Audition asks for a small window of the file, then works on redrawing the waveform, based on surrounding information.

I'd check it out. I haven't seen this feature in SF. Perhaps a future version will have a similar tool. For now, it's worth having the Adobe product just for another "tool" that might serve your need better.

Good luck.

Subject:RE: Spectrum Analysis
Reply by: blackrm
Date:11/18/2004 7:48:10 AM

Thank you for this information. I've downloaded the trial version and will try it this weekend. It looks like a very good feature and we'll definitly look at purchasing Audition if it works well.

Subject:RE: Spectrum Analysis
Reply by: blackrm
Date:11/30/2004 9:44:09 PM

Hello again.

Just wanted to let you know that I downloaded Adobe Audition it the "Repair Transients" worked like a charm on 90-95% of the "mic bumps", basically eliminating them from the wave file (during the spoken portion of it). Coughs were harder to do as it would take them down too far and distort the audio. Thank all of you for your suggestions and help.

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