hmm possible cause
sound card
the female and male plug of the speaker and sound card
speaker
1st test: plugin your speaker into another source of sound to see
if its the speaker or the soundcard problem
if
its the soundcard problem, use a sharp,thin and hard object(which
is enough to reach inside the female hole of the speaker). scribe
it inside to remove the layer of oxydized metal...
den test whether still got become softer
if the problem still persist, its your sound cardproblem liao, go
change it
if its the speaker got problem, remove the oxidise layer of metal
of the male plug.
test it.. if the problem still persist, then its your speaker got
problem. go simlim and buy a new one