There are two "muffin fans" in the avionics racks behind the pilots that sound like the Chicago Fire Department when they are the only thing running (on the ground).
I never noticed them with a headset or helmet on, frankly, but when you are on the ground with external power, they are a real pain.
We did have a spy in the EC factory, but he came back eating frogs and talking funny, so we shot him with a mini-gun.