Acer aspire speakers

Hi, Clet,
sometimes is problem with the fans or hot place, say...beside wall or microwaves.
Be advice that common static noise start on problems with mobo.(sometimes).check cables too. and clean according.
good luck

i had the same problem on my acer aspire 6935g.

its the internal subwoofer.

i have windows 7, so to turn it off i did this:

right click the speaker icon at the bottom right.
click 'sounds', then 'playback'.
double click 'realtek speakers'.
click 'levels', then at the bottom there is a slider saying 'internal subwoofer'.
slide this to 0.
click 'ok', then close all the windows.

The internal subwoofer is off, (but can be turned on again if you want), so the crackling should have stopped.
It worked for me...

Hope this helped! ;D