Macbook Pro Retina 13" continuous idle fan noise

Hello,

My MBP has recently started emitting a constant noise as if the fan is rubbing. Have a listen to the noise here: https://soundcloud.com/adam-wilkie/fan-noise-2/s-VnBbe

It sounds mechanical and is constant from startup to shutdown and is really really annoying. I can hear it most of the time and it is especially audible in a quite room.

I have taken it too the Genius bar twice and they have run their diagnostic tests (which said everything was ok) and have cleaned it out but the noise continues.

Has anyone else had this issue?

If anyone could offer me some advice that would be great!

Thanks