Audacity Mac 1.3 Beta - solved my problem but how?

[Rhymester]

I had some old camera tape based recordings that had an intermittent high pitched tone spoiling the audio. I read up on this and tried the noise reduction filter in audacity. I still ended up with those strange metallic bubbling noises even if I reduced the level of reduction to the minimum.
I then read that the new beta version of Audacity on the mac had a facility to exclude all sound above a user defined threshold.
So, I downloaded the beta version and opened up my file... The strange thing is that when I played back the file in this new version and even when I exported it the high pitched tone had disappeared and so had lots of the background noise but I didn't do anything but open and resave the file. I'm not complaining but am mystified as to why this should happen.

[lordsmurf]

You didn't do it right.

There's also inconsistencies amongst playback codecs.

Post a sample, PM me a link to the file/post, and I'll look at it when I get some spare moments.

[Rhymester]

You didn't do it right.

There's also inconsistencies amongst playback codecs.

Post a sample, PM me a link to the file/post, and I'll look at it when I get some spare moments.

What didn't I do right? I just had a file with problem audio which was audible when opened in VLC, QuickTime and the non beta version of Audacity. When opened in the beta version the problem mysteriously vanished...

[ronnylov]

Maybe the pitched sound was not from the audio file but from your computer? With the sound circuits on the motherboard you can get noise for example when scrolling a webpage, especially if you have headphones connected directly to the sound output. But it does not explain why it was not there next time you tried it. Maybe there was a playback problem in the first audacity version that was fixed in the beta? Or maybe you have made a driver update?

Anyway I read that one method to do noise reduction is to save a copy of your original track. Apply noise reduction of one track and then mix them back together. You will get some noise back and you will reduce some of the artifacts of the noise reduction. If to much noise, then decrease the level of the original track, if to much artifacts by the noise reduction then decrease the level of the denoised track in the mixer.

If there is a distinct tone of a constant frequency you want to remove then you can try a notch filter on this frequency before applying the noise reduction.

[Rhymester]

Thanks Ronny - I was going to try the things you mentioned apart from your tip about mixing tracks back together but found I didn't have to.
Sounds are definitely on audio track even when played back from camera through TV so nothing to do with computer.
I was just wonderiing how simply opening a file in the beta Audacity could make it sound better and remove high pitched sounds without me doing anything.

[ronnylov]

If the problem was in the original file but not in the resaved file then something must have been changed. Can you check the original file in camera and see if there really was a problem? If so, then try to open it and save it in audacity beta and see if it gets fixed again.