27 years ago (omygod!) I was sitting in the upper deck of a brandnew ANA 747SR on the ramp at Haneda, while a dozen line mechs pored over the shiny new cockpit. All was relatively quiet - but then I heard this foghorn-like sound, and I wondered what in a 747 could those guys have actuated that sounded like
that. 
After discreetly looking the situation over, and finding nothing relevant, I happened to glance out a portside window - and at least 500 m. away, there was an ANA TriStar cranking up. You couldn't miss the cloud of fuel vapor behind #2 engine. As the vapor lessened, so did the foghorn.
