Automatic removal of mouth smacks

Using Nyquist scripts in Audacity.
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kozikowski
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Re: Automatic removal of mouth smacks

Post by kozikowski » Mon Oct 21, 2013 5:57 pm

for removal of FM hiss, to use a notch filter?
You can get rid of almost all FM hiss by dropping stereo. Does your receiver do that? Mono FM is remarkably hiss and interference free. I had a very old Dynaco receiver that would drop stereo with a switch. It's amazing what 20dB less noise will do for you. I did all my radio talk show recordings like that for years. The basic mono FM channel is 20Hz-15KHz and I think the proof noise floor is something like -55dB. Stereo was the problem and widely condemned when it was introduced.

Koz

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Re: Automatic removal of mouth smacks

Post by waxcylinder » Mon Oct 21, 2013 6:02 pm

kozikowski wrote:You can get rid of almost all FM hiss by dropping stereo. Does your receiver do that?
Yes it does have a mono setting (and I did realize that that removed the hiss) - but I was kind of hoping to retain the two stereo channels so I can retain stereo images - those BBC engineers are rather good in the live sessions ;)

Peter.
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steve
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Re: Automatic removal of mouth smacks

Post by steve » Mon Oct 21, 2013 6:12 pm

Noise Removal is probably best for reducing FM hiss, but I'd not attempt to eliminate the hiss altogether, just reduce is a bit and preserve as much sound quality as possible. With a good FM antenna I'd expect you to end up with something sounding a lot more pleasing than 128 kbps dab radio, even if dab is hiss free.
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Re: Automatic removal of mouth smacks

Post by Paul L » Mon Oct 21, 2013 6:28 pm

I was being foolish, I overlooked the phase of 90 without which it didn't make sense.

So steve is smoothing in time and frequency both.

Do you think that will be much improved over either smoothing alone?

How is the rolloff of lp compared with lowpass2, etc. ?

I might attempt something more complicated that adapts the cutoff to the click, uses highpass for low-frequency clicks in sibilants, blends more of the original sound so as not to silence the bad frequencies but only make their amplitude similar to the surrounding sound, etc.

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Re: Automatic removal of mouth smacks

Post by steve » Mon Oct 21, 2013 6:51 pm

The HP and LP filters are only 6 dB/octave, hence repeating them a few times. The reason for not using (for example) LOWPASS4 is that for HP and LP the corner frequency may be a sound whereas for the others it can only be a number.
Paul L wrote:Do you think that will be much improved over either smoothing alone?
Smoothing only the frequency works well except for the start and end of the selection, which will both suffer a glitch. The short crossfade at the start and end of the selection will look after that, though there is a very slight "wobble" in the frequency response during the cross-fade due to phase differences between the filtered and unfiltered audio.

Worth noting that even when the filter frequency is at half the sample rate, there will be a slight attenuation of very high frequencies. I doubt that will be a problem with speech, but for a musical application, compensation could be applied with a high-shelf filter close to the Nyquist frequency.
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Re: Automatic removal of mouth smacks

Post by steve » Mon Oct 21, 2013 6:59 pm

Paul L wrote:I might attempt something more complicated that adapts the cutoff to the click
Certainly - was just passing on some ideas.
Paul L wrote: blends more of the original sound so as not to silence the bad frequencies but only make their amplitude similar to the surrounding sound, etc.
You may need to be careful when mixing filtered and unfiltered audio. The difference in phase can cause radical changes to the frequency response. As an example. try this code snippet and look at the frequency response:

Code: Select all

(setf white (mult 0.6 (noise)))

(sum 
  (mult 0.5 (highpass4 white 1000))
  (mult 0.5 white))
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Paul L
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Re: Automatic removal of mouth smacks

Post by Paul L » Mon Oct 21, 2013 7:57 pm

Yes, phase problems.

You did not answer the other implied question: what good would it be to do time smoothing, but not frequency smoothing? In other words, just lowpass at a constant frequency.

How high to most people hear? I am not too concerned about what happens near the Nyquist frequency, because as I explained elsewhere, the ultimate retail version of my productions truncates frequency data above 10kHz in even the best quality version.

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Re: Automatic removal of mouth smacks

Post by steve » Mon Oct 21, 2013 8:41 pm

Paul L wrote:You did not answer the other implied question: what good would it be to do time smoothing, but not frequency smoothing? In other words, just lowpass at a constant frequency.
There was an implied answer to your implied question ;)
"though there is a very slight "wobble" in the frequency response during the cross-fade due to phase differences between the filtered and unfiltered audio."
You'll need to experiment to see if that effect is significant in your application.
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waxcylinder
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Re: Automatic removal of mouth smacks

Post by waxcylinder » Tue Oct 22, 2013 10:25 am

waxcylinder wrote:Ahhh useful feedback there Steve :ugeek: - thanks for that - and this is me writing that down - as Koz says :)

I'll do some experimenting with my next FM capture...

Peter
I like that so much that I wrote in down in the (2.0.6) manual on the Noise removal page: http://manual.audacityteam.org/man/Noise_Removal

Peter

And apologies to Paul for hi-jacking his thread for a bit - but that insight from Steve was interesting and useful :)
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Paul L
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Re: Automatic removal of mouth smacks

Post by Paul L » Tue Oct 22, 2013 1:43 pm

Not at all, waxy, I'm glad for the better understanding of noise removal.

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