A mechanical groan sound effect like that of a large air conditioning unit. It would also probably sound good as spaceship background noise. Mechanical,
External AC Unit - moderate sized. Running/switching off/switching on/running. Running section easily looped. Great for background or foreground. Recorded approximated 5 feet away. 1:08 total. Mechanical,
Mid sized external a/c unit. Approximately 50 secs of steady, slightly flutuating, medium sized commercial a/c (external) unit noise at close range. Mechanical,