If it is not coming from your normal speakers it may be the internal speaker and you are hearing some sort of alarm. For instance if a processor is over heating or a fan not spinning. I would look into that.
Yeah, i'v check the processor temperature (normally < 50º) all the fan's are spinning. I only want to disable this alarm, but thank you for the help
If it is an alarm from the bios you can turn them off usually in the bios. However that can be dangerous if a real issue arrises. Something is likely triggering this, as you already know, what is doing it is the question.
You might want to go through and reseat all cards and cables and see if that helps.