Speaker issue - grainy noise

[kiseki_o_o]

I have a new set of speaker which has a grainy noise issue.

My last speaker had this same issue and thought it was due to old age and faulty cable.
Then I purchased this new set and I never imagined the same issue occurred after 2-3 months of this new speaker.

The noise is there even when the PC is turned off, so this is most likely a speaker hardware or cable issue. Maybe speaker position could also be the cause? or maybe dust?
I couldn't really describe "grainy noise" but I think you guys know what I mean.

I'm about to get another new speaker, but could anyone help to put a light for me what could be the cause for this? I don't want to get another new one and having the same issue again.

Thanks.

 

[buwish]

I'd first test the location theory out, as there may be something around that is causing interference, i.e. the noise you are getting when the PC is off. Try moving it around a bit. If that doesn't work, it sounds like it could be a cable issue.