Low pass filter

[lorela]

To reduce a bad noise (bzzz......) on my guitar track (realized directly by mono-micro-jack from guitar to PC without intermediate tools) I applied a low pass filter (1888 Hz). Search of Hz value was made trying step by step. Then I applied the noise removal effect and the final result is good, but not perfect (there is still a very light bad noise).

I'm a new Audacity user and would like to know if it's possible to have better results.
(Audacity 1.3.13.beta on Windows xp)

Thank you, Lorela

[kozikowski]

Removing hum is a snap with the filtering tools, removing buzz is very serious and may not be possible. Buzz has the same properties as the music. The Noise Removal Tool in Audacity 1.3 is the only tool I know of to filter out that kind of trash. If that didn't work, the performance may be gone.

Noise Removal is intended to remove light, barely annoying interference. If the buzz is the same volume as the show, that's the end. Even in Audacity 1.3, the removal is likely to damage the musical notes.

Try increasing the Reduction -- the top slider and pay attention to what it's doing to the music.

Koz

[steve]

Could you post a short, unprocessed sample of your original recording.
Select a couple of seconds from the recording - preferably including so "buzz only" and some actual music, then use "Export Selection" and export as a WAV file.
If the file is less than about 6 seconds duration you will be able to attach it to your reply (see "Upload Attachment" below the compose message box).

[lorela]

Steve and Koz,

thank you very much for your instructions.
I'll apply them soon.

Lorela

[lorela]

Steve,

Sorry for the delay in reply.

I attached a 6 second of guitar + noise.

Lorela

[steve]

That's going to be very tough to clean up.
Here's the Spectrum View of the track:

firsttrack001.png (351.23 KiB) Viewed 1556 times

Those red horizontal lines that continue throughout the track are the individual frequencies that make up the buzz. To remove the buzz, all of those frequencies needs to be filtered out. This can be done using the notch filter (available in Audacity 1.3.13) but the notch filter can only remove one frequency at a time and there are dozens of frequencies to be removed.

Also, the waveform is not centred around the horizontal zero line - it is shifted significantly below the middle of the track. This is known as "DC offset" and is a common problem with poor quality sound cards. There is a setting in the Normalize effect that will correct the DC offset. Here you can see the DC offset in the upper track, then correctly centred in the lower track.

tracks002.png (20.48 KiB) Viewed 1556 times

[lorela]

Steve,

The things one can do with Audacity are really interesting.
I need some time for try the operations you indicated me.

I understood it's a good thing to have a good sound card and a better workstation.
For music I'm working on an old computer.
I need a new one, but I need to know and possibly acquire all the tools for make good tracks.
I count to do it step by step.

Thank you for your kind reply,

Lorela

[kozikowski]

There are ways to buy equipment that work very well but are dead-ends. Not expandable. The very good quality USB microphones are in this camp. One microphone is perfectly OK, and many podcasts have been done with them. Two dips into black magic and sorcery and you can't do three at all.

When you get settled, post back here and tell us what you're going to do, for what kind of performance, and what, if any, expansion you want. We'll tell you if there's anything wrong with what you're doing.

Don't buy everything and then post when parts of it don't work right.

"I bought a Frammis mixer and want to mix twelve microphones."

"A Frammis mixer will only amplify eight microphones. Did you keep the receipts?"

Koz