Retina Macbook is emitting a noise from under keyboard
(Writing this up from a discussion in the comments, to help future readers...)

The noise in the sound recording is a high pitched buzzing noise, which plays for approx 1 sec, then off for a second, then on for a second again.

Some suggestions of things to try, in order to isolate the noise to a particular part of the system:


change the screen brightness
change the keyboard brightness
test with the main battery discharged &amp; charged
test with a pair of headphones plugged in
test with mains charger plugged in &amp; removed
test with an application generating high CPU load
test with an application generating high GPU load