Tracks sound great in Audacity, distorted after export

[mwgainesjr]

I've never recorded with Audacity or any other program before......So I wanted to experiment and I went to radio shack and bought a 5 dollar 1/4 input to 1/8 input converter where I can plug my guitars and mic into the sound card of my computer and downloaded Audacity....Everything went awesome. Put a mic in front of my drums and using an acoustic youtube recording of my song I was able to lay down the drum track. It wasn't perfect and wasn't completely on rhythm at times but it was good enough. Then plugged my acoustic in and put down the rhythm guitar. Both drums and acoustic come in as mono so copied the tracks to another track, put on full left and the other full right. It sounded good. Plugged in my electric and laid down the lead....this came in stereo and sounded very crisp....plugged the mic back in and laid down the vocals. this came in mono so i doubled it and went one right and one left. I got it sounding really good giving the drums a bass boost and adjusting the gain accordingly.

Play back in Audacity was excelent and I was very satisfied.

I exported it to MP3 and the MP3 vocals and part of the acoustic is distorted!!! it sounds great in Audacity but not when exporting to MP3 or WMA.....any ideas? All that work for nothing? I'm guessing the issue is that when exporting to MP3 or WMA it converts it to two channels and things get distorted with not all tracks being stereo...and now I go back this morning and my Audacity project is distorted now......what am I doing wrong besides using cheap equipment? lol It did sound good....

TIA

[steve]

When you play the project in Audacity, look at the (green) playback meter.
What is the maximum level that it indicates? Does the red "clip" indicator near the 0 dB mark show up?
(see here: http://manual.audacityteam.org/man/Meter_Toolbar )

[DVDdoug]

I can explain what's going on, and I can give you some hints, but I haven't actually used Audacity for mixing, so I can't really help with the details.

When you mix, the samples are literally added (summed) together. Analog mixers use an analog summing amplifier. (And of course, analog mixers have level controls on all of the inputs to adjust the levels before mixing and a master level control to adjust the level after mixing.)

If you take two tracks that have 0dB (maximized) peaks, and you mix those two tracks together, your file will (probably) "try" to go over 0dB and clip (distort), depending on how the peaks line-up in time.

A 6dB change represents a factor of two volume change. So, if you want to be sure that two mixed tracks won't clip, both tracks need to peak below -6dB before mixing. If you are mixing 4 tracks, each track needs to peak below -12 dB. ( You don't have to record at these low levels, but you have to mix at lower levels.)

If the level is too low after mixing, you can "normalize" final-mixed file to bring the peaks back to the maximum of 0dB. (If it still doesn't sound loud enough you need compression, but that's another story...)

it sounds great in Audacity but not when exporting to MP3 or WMA.....any ideas? All that work for nothing?

Audacity (like most audio editors & DAWs) uses floating-point for internal operation & temporary data storage. This allows the data to go over 0dB without clipping (you can still clip the digital-to-analog converter if you have the volume cranked-up).

But most audio file formats use integers. There is a limit, and the file can be clipped when you render/export.