sounds do not play, or stop at the wrong moment.

I have a selection of 5 mp3 sounds of 14kb, and all about 0.2 secs long. the sounds are preloaded. one of them is randomly picked and played when the spacebar is pressed. I use one channel that contains one of the sounds at a time. so when the spacebar is pressed again, the sounchannel will contain that new sound file.
no problems when i press the spacebar with about 2 secs between presses. when i press it often, the files are sometimes not played, or stopped halfway. this is expectable. but how do i solve it?

also about soundchannels in general. i don't really understand their purpose. is it so you can play the same sound at the same time with different soundchannels?

also my fps drop with 4-6 everytime i press space. is there something to do about that?