When they don't feel like making noise and at night.
Check your AOL messenger settings. That's the sound of a buddy signing in or out.
Because without power, the hard drive, the fan, they make noise when they have power. Without it, they all stop making the computer go "quiet."
Lubricate.
The only reason your mac would make noise is if it is cleaning its self. If you first get a mac it might clean its-self more often. Once the mac is comfortable in its new home it will stop making the noise. I work at the apple store, and I can a sure you that your computer is fine. Remember to stay calm because all macs do make the sound, it is completely normal, and your mac will eventually stop making the noise, once it is use to it place.
making
Unplug it.
Bleeding the air from them usually helps.
either replace them or add motor honey to go for a longer perion without noise....
no
Ensure the cable is plugged in correctly
Racket