buzz in exported mp3 file

Working with Audacity 2.0.3, installed from dmg on imac osx 10.6.8.
My audio file sounds fine in Audacity but when I export to mp3 I have a loud buzz for the first 4 sec. Then it stops. !?
Any suggestions?
I reexported and saved as another file name and still the same buzz.

Does it happen with more than one show? Post a sample of the noise on the forum.


Yes, actually it seems to happen again on another file.
I’m attaching the file here.
Farm-music.aup (3.13 KB)

AUP is not a sound file. It’s an Audacity project manager. It’s a text file.
Choose one of the other formats. Go back to the instructions.

see attachment

file was too large, now it’s ok… below

Right this second, I have no idea at all. Does it do that if you Export as WAV (Microsoft 16-bit PCM)?

Sometimes I use the gun technique. If somebody has a gun and said I had to intentionally make that damage, how would I do it.

Heck if I know.

You see during the first four seconds, the blue waves are bigger than normal? Are they big in the show while it’s in Audacity?

Upload a short segment with silence – no music, over four seconds, where the damage would normally be.

Totally wild guess, are you exporting the show to a USB hard drive?


We know a few more items. The damage presents as a sharp triangle wave in the middle of an otherwise normal sound performance (2). If you look closely, there are samples within the triangle wave. I have no idea what that means other than damage that the digital system is trying to follow. Severe digital damage I would expect to be greatly misplaced samples, not neat and orderly like this.

The signal is periodic. It occurs about every 19 mSec (1) It occurs just slightly off 20mSec which is the repetition rate of 50Hz power. That may be a complete red herring. Or not.

If I had to make up something out of thin air, I would say the signal being recorded on the hard drive is experiencing damage during the time the drive spins up. Spin-up or starting any electric motor requires the highest current from the supply system. The user is in a 50Hz country like Britain or other country on the continent and their power system is in trouble.

This should happen with any export, MP3 or not.

Anybody can jump in here…

Screen shot 2013-04-22 at 10.48.16 PM.png
Screen shot 2013-04-22 at 10.47.38 PM.png

I may have stumbled on a work-around: If I mix and render before I export, I don’t think I get the buzz. (Ver. 2.0.3 on OS 10.7.5.)