My laptop has a fully updated installation. I have an annoying problem when running on battery - the laptop makes a barely audible but very annoying noise which goes something like: beep followed by a sound of something spinning up (i.e. a fan or a harddrive). This happens at apparently random intervals when running on battery (there seems to be a correlation to my activity on the laptop) and never happens when running from a power supply.
As far as I can tell, Configure Your Desktop --> Power Management does not have any settings for CPU, fan, or harddrive, which are the things I would associate with a sound of something spinning up.
Besides the fact that this sound is very annoying, I am concerned that some motor in my hardware is constantly having to spin up and down, thus reducing it's lifecycle. Does anyone know what this could be? Or better still, how to stop it from happening?