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Passing planes and other whoosh sounds

windytan.com

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Re: Passing planes and other whoosh sounds

#31

Post by jeffbee »

nicemountain wrote: post #10
shmeeed wrote: post #7

I'm just armchair musing here, and I'm definitely no expert on sound waves, but I wonder if they considered the fact that most airliners have more than one engine. Could the effect also be the superposition of multiple engine sounds? Those have a fixed spatial distance, too, and the effect would (I suppose) change with the lateral angle to the listener during the fly-by. This theory should be pretty easy to falsify,…

For that, the pressure waves (sound) coming from the engines would have to be somewhat coherent, or correlated in phase. Since what we're hearing is essentially turbulence, that's not going to be the case.

Engines in modern aircraft are phase-locked, though.

Re: Passing planes and other whoosh sounds

#32

Post by mrob »

jeffbee wrote: post #31
nicemountain wrote: post #10

Earlier quoted context omitted.

For that, the pressure waves (sound) coming from the engines would have to be somewhat coherent, or correlated in phase. Since what we're hearing is essentially turbulence, that's not going to be the case.

Engines in modern aircraft are phase-locked, though.

The majority of the engine noise is caused by the turbulent mixing of the exhaust with the surrounding air. Turbulence is chaotic, so even if the engines are phase locked the sound rapidly becomes incoherent.

Re: Passing planes and other whoosh sounds

#34

Post by 0_____0 »

larusso wrote: post #29
meindnoch wrote: post #24

Earlier quoted context omitted.

Everyone should try a real anechoic chamber once. The silence there is deafening .

Don‘t know if this is the same but I went to Death Valley on the Devil‘s Golf Course during summer. There was no wind no nothing. It was so damn silent. Wonder how that compares to an anechoic chamber now.

Having experienced both, it's very similar.

Edit to add: I've been in an anechoic chamber and also the black rock desert, which is dead flat and thus has very little surface area oriented to reflect sound back at the listener, which makes it similar in that you don't experience environmental reflections.

Devil's Golf Course has more "texture" to it but if you were quiet on a windless day I think the effect would be similar.

Re: Passing planes and other whoosh sounds

#35

Post by Toutouxc »

jeffbee wrote: post #31
nicemountain wrote: post #10

Earlier quoted context omitted.

For that, the pressure waves (sound) coming from the engines would have to be somewhat coherent, or correlated in phase. Since what we're hearing is essentially turbulence, that's not going to be the case.

Engines in modern aircraft are phase-locked, though.

Do you have a source for that? I’ve heard about something that some twin-props have, but definitely not jets. The engines don’t even run at the same RPM.

Re: Passing planes and other whoosh sounds

#36

Post by jeffbee »

Toutouxc wrote: post #35
jeffbee wrote: post #31

Earlier quoted context omitted.

Engines in modern aircraft are phase-locked, though.

Do you have a source for that? I’ve heard about something that some twin-props have, but definitely not jets. The engines don’t even run at the same RPM.

https://www.osti.gov/biblio/6356085

It is what the "Sync" switch on the panel does.

Re: Passing planes and other whoosh sounds

#38

Post by m3047 »

Ground feature echo (mentioned in the article)... possible. Not mentioned here or in the article: thermocline in the atmosphere. Thermocline in the water is traditionally how submarines "hide" from surface ships.

I hear flanging from the planes incoming from quite a distance, and they're pretty low when the fly over where I live. More telling: I can hear the freeway and the busy arterial, "depending on how the wind blows". Sometimes it flanges, too.

So: ground reflection along with thermocline refraction seems a perfectly plausible explanation for one source of the phenomenon; could be several, probably all involving ground and atmospheric factors.

Re: Passing planes and other whoosh sounds

#39

Post by cf100clunk »

meindnoch wrote: post #24
albert_e wrote: post #18

Tangentially related I once picked up my memory foam mattress and stood it up against one of the walls ... for cleaning the bed or whatever. As I walked past the mattress I instantly noticed that the mattress is such a good absorber of audio waves that I could immediately notice a dip in ambient sound in the ear facing the mattress. The room was already "silent" and this newly discovered lower limit of silence was pr…

Everyone should try a real anechoic chamber once. The silence there is deafening .

If you are handy to an R&D lab that has a combo Faraday Cage/anechoic chamber you can have a nice experience free of RF and audio noise and stimulus. Even better if it is dimly lit in near-infrared. Even better-better if it has a tank of warm water with lots of epsom salts, although I've never been in a lab that had such a thing as a requirement.

Re: Passing planes and other whoosh sounds

#40

Post by meindnoch »

cf100clunk wrote: post #39
meindnoch wrote: post #24

Earlier quoted context omitted.

Everyone should try a real anechoic chamber once. The silence there is deafening .

If you are handy to an R&D lab that has a combo Faraday Cage/anechoic chamber you can have a nice experience free of RF and audio noise and stimulus. Even better if it is dimly lit in near-infrared. Even better-better if it has a tank of warm water with lots of epsom salts, although I've never been in a lab that had such a thing as a requirement.

I'm skeptical of shielding yourself from RF noise having any detectable effect.

Unless you have amalgam tooth fillings, that anecdotally can act as a crude diode, and demodulate strong enough AM signals.

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