Export to MP3 adds 'chirp' to file

[hannon]

I have been transferring r-r tapes by recording an entire side into audacity, saving the project, then extracting individual tracks. After removing removing the dead space from the beginning and end of each track and cleaning up any audio problems, I export to MP3. When I play the file or import it back into audacity a short low frequency chirp appears at the beginning of the file. Occasionally, I can remove the chirp and save back into the original MP3 but sometimes the chirp reappears.

Has anyone else experienced this?

Thanks

[kozikowski]

Does it still do it if you Effect > Normalize > Remove DC before you encode?

Turn the other normalize settings off.

Koz

[hannon]

I'm afraid I was a little presumptuous in my initial post, for which I apologize. Upon further testing, the problem does not occur on export, rather importing a mono MP3 into Audacity. I reopened some files and stored them back and upon replay noticed a burst of noise lasting about .03 sec at the very beginning of the file. If I play the file prior to importing it, the chirp is not there.