what speakers u use currently ? are they magnetically shielded ?
a main reason for buzz sound is electrical disturbance whereas pat pat sound normally occurs due to magnetic interference.
you should thoroughly check these first :
> check ur electric switchboard, there should not be any loose connection. if the switch related to plug is bad, change it. if the plug socket is bad or not good quality, change it.
> use a 3 pin plug connection that joins firmly - not too tight, not too loose, just proper connection.
> always use ups. make sure both computer and speakers are connected to it.
> if ut audio pin is dirty, wipe it and connect it again.
> don't put speakers near heavy electrical / magnetic machinery (i.e. UPS
)
> keep ur cellphone away from speakers
> do not lay audio wires near high power wires. try to keep wires as much tangle free as possible.
try all these and tell.