I have a song file in MP3 format, 1.38 MB, that I edited in Adobe Audition. I cut most of the songs part so it can be just 1 minute. when I was trying to save, I saw a warning saying something about lossy compression or whatever. but i didn't really paid attention to it and saved the file anyway.

Now, I imported that to Adobe Flash CS6 and started working on my animation. On the timeline, whenever I preview using the Enter button, song plays fine. But when I Ctrl + Enter to preview the SWF, sound's quality is very bad :/ anyone have an idea as to why is that?

You can right click on the sound in the library, and open the properties to change sound quality manually in flash. It always seems to default to low quality

btw, it ups the rendering time by a lot, so I suggest you do it after the animation is complete