Speaker beeps and blips

I'm using a set up m-audio DX4 (cheap monitors) on my MBP.

Since 10.4.9 I've heard these strange beep and blips and pop from my speakers usually when stopping a video or stopping music or doing something that involves the soundcard. it can be very annoying.

here's the thing, i used to hear about this issue from other people, and was just waiting for it to get fixed. now i've got 10.5.2 and i still have this problem, and i'm not sure if other people still do. So i'm looking to see if anyone has had/still has this problem.

This only seems to occur with external speakers, the system is fine when using internal.

I would really appreciate some help here.

thanks.