Am I hearing vortices collapse?
Thread Starter
Joined: Jul 2005
Posts: 297
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From: Orstralia
Am I hearing vortices collapse?
I'm a lowly PPL student, and an interloper from JB to boot, so forgive the naivety:
I live near an airport, under the final approach from a nearby beacon. Aircraft go directly over my house at about 800-1000ft by my guess.
The passage of large aircraft (737, 340 etc) is followed by what I took to be an echo.
Listening more carefully, I found that this 'echo' is audible in all conditions - full or partial cloud cover, or clear sky, especially when the ambient noise level (traffic etc) is low.
The 'echo' usually starts a second or two after the aircraft has passed, and begins as a 'whooshing rumble'. Then the odd bit starts. It could be described as a sort of 'longish light sabre zapping noise', if you seen Star Wars. There may be a couple of these noises, which then decay with a faint rumble into silence.
I am wondering if I am hearing the sort of refolding-in of the 'torn' still air, in other words the collapse of the vortices produced in the wake of the plane?
I can't hear anything like it from small craft including small jets, and it seems a little dependent on the approach speed of the large aircraft (there seems to be some variation there).
Does anyone have any idea about this apparent phenomenon?
I live near an airport, under the final approach from a nearby beacon. Aircraft go directly over my house at about 800-1000ft by my guess.
The passage of large aircraft (737, 340 etc) is followed by what I took to be an echo.
Listening more carefully, I found that this 'echo' is audible in all conditions - full or partial cloud cover, or clear sky, especially when the ambient noise level (traffic etc) is low.
The 'echo' usually starts a second or two after the aircraft has passed, and begins as a 'whooshing rumble'. Then the odd bit starts. It could be described as a sort of 'longish light sabre zapping noise', if you seen Star Wars. There may be a couple of these noises, which then decay with a faint rumble into silence.
I am wondering if I am hearing the sort of refolding-in of the 'torn' still air, in other words the collapse of the vortices produced in the wake of the plane?
I can't hear anything like it from small craft including small jets, and it seems a little dependent on the approach speed of the large aircraft (there seems to be some variation there).
Does anyone have any idea about this apparent phenomenon?
