Odd clicking noise coming from left laptop speaker

Hi there. Bit of an odd problem. I have a Samsung X460 - the fan started making a horrible noise so I took it apart and replaced it. Put it back together and all was fine, until I started watching a movie. A few minutes in a strange popping, clicking sound started. It's a bit like the sound you get when you plug a mic or something in, but a bit different, and is repeated several times a second. It comes on just after start up - starts off slower for a second and then speeds up.

I've taken a (not very good) video of it - perhaps that's the best way to explain it. It's at http://youtu.be/FkKoR8fwA-4

Funny thing is, it only seems to be coming out of the left speaker and not the right. It doesn't play through headphones at all. Lastly, I can get sound fine through the headphones but not the speakers - only that clicking sound.

It's almost like the speaker is amplifying some working of the computer. Do you think it could be a loose cable or something, considering I just took the laptop apart?

I'd be really grateful for some help, really not sure what to do apart from take it apart again and check all the connections - something I'd rather avoid unless I'm looking for something!

Thanks in advance...