Problems with the sound!

Now, I don’t know is it just me being stupid (which more likely to be the case), or is it something else?

Here is the problem: I recorded a sound that I want to be played when people roll over the buttons in the menu. I recorded it and exported it as .mp3 and it sounds good when I play it in Sound Forge and Cool Edit. But, when I import it into the movie it sounds horrible, there is a great loss of quality. Then, I exported it as a .wav, but it wouldn’t play at all in the flash movie. I wrote this script to play the sound:

mySound_sound = new Sound();
mySound_sound.loadSound(“click.mp3”, false);
var i;
var numbtn = 7;
var btn = this[“button”+i+"_btn"];
btn.onRollOver = function(){
mySound_sound.start(0, 0);

The script works fine, and it plays the sound but it sounds horrible. What could be the problem?