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Hydrogenaudio Forum => General Audio => Topic started by: Overdrive on 2019-11-13 16:07:54

Title: Noise reduction audio
Post by: Overdrive on 2019-11-13 16:07:54
Hi,

My question is simply but I think that answer maybe is not it.

I have audio from analogic source, that sound low and needs noise reduction.

I had normalized source and fix all distorsions like hum, click, crackles, etc..

Like audio sound off I want EQ audio to to enhance frequencies greater than 4 Khz. Should I apply noise reduction (offline) after or before EQ??

My logic makes me think that after equalization, since it would increase the presence of noise.

Any suggestions??
Title: Re: Noise reduction audio
Post by: DVDdoug on 2019-11-13 17:02:49
Yes, I'd EQ first.     Noise reduction can sometimes introduce artifacts (side effects), especially if the noise is bad.   Boosting the highs might "bring-out" those artifacts and then you might have to go-back and play with the noise reduction settings.   I'd do the noise reduction last so you can hear what it's really going to sound like.   (It would be OK to normalize as the final step after noise reduction and everything else.)
Title: Re: Noise reduction audio
Post by: Overdrive on 2019-11-13 17:34:20
Thanks for your answer.

I had normalized audio before of appling EQ and Denoise. Would not be the noise higher if normalize after?
Title: Re: Noise reduction audio
Post by: saratoga on 2019-11-13 19:33:06
It isn't going to matter when you normalize.  That just changes the average volume level. 
Title: Re: Noise reduction audio
Post by: Overdrive on 2019-11-13 19:53:42
Ok, thanks. All clear.
Title: Re: Noise reduction audio
Post by: DVDdoug on 2019-11-13 19:54:50
Quote
I had normalized audio before of appling EQ and Denoise. Would not be the noise higher if normalize after? ]
If normalizing brings-up the volume, yes it will make the noise more noticeable  just like turning-up the analog volume control.  But, it doesn't change the signal-to-noise ratio.

A couple of other considerations -

EQ will usually change the peak levels so it can mess-up the normalization and it can push the peaks into clipping.   So it's a good idea to normalize (or at least check your peaks) after EQ and before rendering while you're working in floating-point.   (I'm assuming your audio editor works in floating-point so it can "temporarily" go over 0dB without clipping).

If you have a digitized vinyl record with a really bad click, that click can be the loudest thing in the recording and that will affect normalization.  

It doesn't hurt to normalize more than once so if you want to normalize first and then again as the last step that's OK..
Title: Re: Noise reduction audio
Post by: Overdrive on 2019-11-13 21:15:19
Ah, I understand. I am working with Izotope RX therefore I will let your instructions because I did not check the peaks after EQ. Thanks.

EDIT: Thanks at your suggestions I can avoid ruin the audio because after EQ had been clipped. Thank'u so much.
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