Whenever I enable the "Intel Speedstep technology" in the BIOS power configuration, I can hear noise when operating the laptop. The noise is sometimes a clicking noise in idle-mode or a buzzing noise (similar to the noise when reading from a spinning disk) when doing low work tasks (scrolling, moving the cursor, ...). I don't know if the noise is present when doing high work tasks, as that turns on the CPU fan, which is otherwise off.
When turning off the Speedstep technology, the noise is far less pronounced, but still barely noticeable in a silent room.
I could find another report that links high pitched noise with intel CPU power configuration: http://www.tomshardware.co.uk/forum/324507-31-high-pitch-noise#r5308173 Though, that report does not include any causes for the noise and presents only a workaround.