When I am seated in my aircraft I hear my cockpit sounds and my engine sounds.
If I shut my engines down, I hear the nearby aircraft's engines, (if they are running).
If I move outside of my aircraft I hear my engine sounds, (if they are running), and as I move (Yaw) around the area I hear the other aircraft's engine sounds, (if they are running).
Zooming into them makes the sounds louder, and panning around varies the intensity of the sounds.
Paul...I like sounds...

...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.