help getting rid of buzzing on audio

[slimwaffle]

I have a DVD with a loud shrill, crackling, buzzing on the audio throughout. I demuxed it and now have an audio wav file. I've tried the noise removal in Audacity (selected a section of audio that's silent except for the buzzing, get noise profile, select the whole file) many different ways (even going so far as setting all the sliders in step 2 all the way to the right. This turned the sound to mush, but the buzzing was still loud and clear) and it's not making the slightest difference in the buzzing. I'm using version 2.0.3 on Windows 7 x64 SP1. Is there a script that would help fix this? I ask this because I tried the script in this thread (http://forum.audacityteam.org/viewtopic ... 11&t=11760) for a hum on a different DVDs audio and it worked like a charm. Any help with this would be greatly appreciated. Thanks.

This is possibly a useless piece of information:
Odd thing I noticed it the top of the sound wave is higher than the bottom of it. Both right and left channels are identical, it's that the bottom of each is around -0.5 and the top goes a good deal above 0.5. Not sure if this is actually odd but I remember waves looking uniform on top and bottom.

[kozikowski]

We arrived in the middle of the second act.

I have some home-made movie DVDs..??
I'm trying to rip BlockBuster Video DVD movies..??
I'm trying to edit camera-burned Data DVDs..??

You have a collection of very highly unlikely symptoms so we need to know more background. What exactly are you doing?

Koz

[slimwaffle]

It's a DVD I bought from FYE. It's a cheap bargain bin one that's sourced from a VHS (complete with overscan line along the bottom of the screen). I own a VHS of it too (which wasn't as cheap). It has the same buzz. My plan is to fix the audio so I can watch it, because as is it's like nails on a blackboard.

[Gale Andrews]

Can you export a WAV file a few seconds long containing some noise on its own followed by noise with some signal (audio you want to keep). See http://forum.audacityteam.org/viewtopic ... 49&t=64936 for how to attach files.


Gale

[slimwaffle]

Thank you for the reply, Gale. Here is a clip. Also I've been fiddling with the file and the only thing I've found that gets rid of the buzzing is the Paulstretch effect. It also ruins the rest of the audio, but something in that effect is helping with the buzzing so...

[Gale Andrews]

Noise Removal won't get rid of much of the crackling, and I think the crackle is too widespread in the upper frequencies to use Notch Filter. If you want a quick method, just open Equalization and reduce all the frequencies above 800 Hz by 30 dB (in Graphic EQ, move the sliders down).

It will then sound very dull and you will almost completely lose the trumpets at just after 4 seconds but you will also lose the crackle (attached).

Cut the frequencies above 800 Hz by less than 30 dB to keep more treble and more crackle.

You may want to try selecting and Edit > Duplicate on that trumpet fragment (or any other bits where the crackle is not too bad) which will then preserve it and mix it in with the EQ'ed track. You may want to turn the -....+ gain slider down on the original track where you keep any original fragments that are worth keeping.

I am not an audio engineer so those here who are may have other ideas.


Gale

[Robert J. H.]

A smart DSP-trick to reduce noise in the upper regions (while keeping a proportional big amount of the useful signal) is to average the samples.

Code: Select all

(snd-avg s 7 7 op-average)

Put the code into the nyquist prompt and press OK.
The value 7 is the amount of samples that are averaged. Higher values result in higher attenuation of the noise (and higher frequencies as well). Give it a try.

[slimwaffle]

Thanks, Gale and Robert. I tried the lowering the EQ. Moved all the sliders above 800 Hz all the way down and get muffled sound and the buzz is still there. And when using the Nyquist avg code it returns a "Nyquist did not return audio." dialog box.

[Gale Andrews]

Thanks, Gale and Robert. I tried the lowering the EQ. Moved all the sliders above 800 Hz all the way down and get muffled sound and the buzz is still there.

What are you trying to get rid of? I thought you meant the "crackle" distortion that is there slightly in the background noise and actually increases when the music occurs.

Has what you want to remove been removed from the sample I attached?

when using the Nyquist avg code it returns a "Nyquist did not return audio." dialog box.

That code seems to fail for stereo audio. If I make the track mono (Tracks > Stereo Track to Mono) that code truncates the audio and speeds it up. If you use Change Speed to slow it down again you can hear a very bright sound with the crackle reduced but not removed.


Gale

[kozikowski]

Maybe we're working at cross purposes, I didn't hear any shrill, sharp buzzing in the test clip, either. Just the occasional crackle. Koz