bit of a quandry are the same decibels and sound frequencies experienced from below a fighter jet going overhead as been above the fighter jet.
lets say it was flying 1000 feet above ground level
would or what could be heard 1000 feet above its flying level
to what is and can be measured at ground level
please move to appropiate section mods thankyou
lets say it was flying 1000 feet above ground level
would or what could be heard 1000 feet above its flying level
to what is and can be measured at ground level
please move to appropiate section mods thankyou
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'tis moved 🙂I believe cloud cover greatly affects how the sound of aircraft are perceived at ground level, similarly temperature differences of different air layers also plays a big part...
I know nothing more 😀
I am well aware of the inverse square law
But is this in all directions from point of source regardless of altitude
Or just a ground level/ sea level mathematical equation
😱😱
But is this in all directions from point of source regardless of altitude
Or just a ground level/ sea level mathematical equation
😱😱
1) It is true at all levels.
2) direct signal will be same in all directions (assuming jet exhaust is omnidirectional) at the same distance, but at ground level (or, say, a few feet above ground) it will be slightly higher because of ground reflections.
But, , 3dB higher if reflectivity is 100%, which will actually depend on surface material and texture.
2) direct signal will be same in all directions (assuming jet exhaust is omnidirectional) at the same distance, but at ground level (or, say, a few feet above ground) it will be slightly higher because of ground reflections.
But, , 3dB higher if reflectivity is 100%, which will actually depend on surface material and texture.
If your ear is within an inch of a good reflecting ground (polished concrete) ground, SPL will bump 6dB. If a few feet up you have 6dB bumps with nulls between (classic comb filter).
This can easily be seen today with a hiss source, small mike, hard wall, and a PC with spectrum display.
I can't believe this is the real question. A fly-by is a very quick event; at the proposed 1000 feet it is faster than my SPL Meter's needle. And who is sitting 1000 ft *above* a jet aircraft?
This can easily be seen today with a hiss source, small mike, hard wall, and a PC with spectrum display.
I can't believe this is the real question. A fly-by is a very quick event; at the proposed 1000 feet it is faster than my SPL Meter's needle. And who is sitting 1000 ft *above* a jet aircraft?
At this QTH, old enough to remember the jets practicing over the Nike missile bases in Northeast OH in the late 1950's. Last time I heard a real sonic boom was 9/11 when they had been called out and were screaming over our 'burbs in NY and NJ.
At the Air Shows in OH and NJ they don't hammer. Don't know about Oshkosh!
At the Air Shows in OH and NJ they don't hammer. Don't know about Oshkosh!
I can remember the F-104's flying out of Homestead AFB cracking the sound barrier over our rural house west of Miami. It was about 1966 or 67.
A neighbor told me that his TV lost it's picture at the exact moment that one of those sonic booms occurred. He asked if I could check it out. Removing the back from the old B&W TV set revealed the obvious, a white topped horizontal output tube, no visible glass damage though. Coincidence?
A neighbor told me that his TV lost it's picture at the exact moment that one of those sonic booms occurred. He asked if I could check it out. Removing the back from the old B&W TV set revealed the obvious, a white topped horizontal output tube, no visible glass damage though. Coincidence?
6 dB boost for coherent sources, 3 dB otherwise. So a single engine plane should be 6 dB and multiengine depending on listening position could only be 3 dB from ground reflections.
However above and below may differ depending on altitude due to distance and air pressure. It will also differ to to climb angle and engine mounting. Underwing mounting will of course affect sound projection.
Of important note is anywhere near a jet engine requires effective hearing protection!
Now for those of you near airbases, you will know when a war starts. The jets will takeoff at full speed. That means full afterburners. The result will be broken windows! They can use all of the extra fuel because they can be midair refueled on the way back, if they are coming back! (This is truly bravery going out when there are significant chances you are not coming back.)
However above and below may differ depending on altitude due to distance and air pressure. It will also differ to to climb angle and engine mounting. Underwing mounting will of course affect sound projection.
Of important note is anywhere near a jet engine requires effective hearing protection!
Now for those of you near airbases, you will know when a war starts. The jets will takeoff at full speed. That means full afterburners. The result will be broken windows! They can use all of the extra fuel because they can be midair refueled on the way back, if they are coming back! (This is truly bravery going out when there are significant chances you are not coming back.)
Pretty sure it's illegal for commercial aircraft to exceed Mach 1 over land or close to land in the US. No doubt the military can do what they want, but I think they avoid it as well. When you hear sonic booms, it might be time to put your head between your knees under your desk.
On the original question, how fast is the aircraft moving? Are the mics moving at the speed of the plane? If the mics are moving, there's probably a speed where you don't hear anything at all. If fixed, the ground reinforcement is probably the simple case above.
On the original question, how fast is the aircraft moving? Are the mics moving at the speed of the plane? If the mics are moving, there's probably a speed where you don't hear anything at all. If fixed, the ground reinforcement is probably the simple case above.
There might have already been a tiny crack (thermal?) not yet going through glass thickness, or some similar "accident waiting to happen" and the sonic boom could have been "the straw that broke the camel´s back".
Not necessarily flexing/shaking the tube itself, but the chassis, cabinet, even the table it was sitting on.
As of the OP's question, I see it a rethorical one, the fighter jet being just an example.
Main doubt seems to be about symmetry which I would assume considering short distances involved, not enough for a significant change in atmosphere density.
Now if jet fighter wers, say, 5 miles high, then density below would be WAY higher than density above.
Not necessarily flexing/shaking the tube itself, but the chassis, cabinet, even the table it was sitting on.
As of the OP's question, I see it a rethorical one, the fighter jet being just an example.
Main doubt seems to be about symmetry which I would assume considering short distances involved, not enough for a significant change in atmosphere density.
Now if jet fighter wers, say, 5 miles high, then density below would be WAY higher than density above.
All I know is my desk at work is essentially at the end of the runway at Miramar MCAS. We have to pause our meetings whenever a fighter wing takes off. Ospreys and logistics craft (C130) are much quieter.
The F22s yesterday had a distinctive sound compared to the litany of F18s.
Ed, for all intents and purposes, a single vs twin engine is a point source from 1000 ft, no?
The F22s yesterday had a distinctive sound compared to the litany of F18s.
Ed, for all intents and purposes, a single vs twin engine is a point source from 1000 ft, no?
Guess so.
Beside, jet noise is white noise, not the slightest resemblance to sinewaves.
At most, white noise with some pipe resonances colouring it, but nothing further.
Beside, jet noise is white noise, not the slightest resemblance to sinewaves.
At most, white noise with some pipe resonances colouring it, but nothing further.
Military fighter airplanes (jet engines) have different sound spectrum from commercial airplanes (high bypass fan jet engines), none of which are "white noise"
https://asa.scitation.org/doi/pdf/10.1121/1.4895772
https://www.ndt.net/article/jae/papers/26-290.pdf
Ed points are valid
George
https://asa.scitation.org/doi/pdf/10.1121/1.4895772
https://www.ndt.net/article/jae/papers/26-290.pdf
Ed points are valid
George
We live about 25 miles from Tyndall AFB and get at least 3 or 4 sonic booms a month.....makes you jump fer sure!
They are all different frequencies, I could hear an AWACS over the gas powered lawn mower I was pushing, and knew what it was I was hearing before I saw it. Could also hear one through modern e-glass in an office building.
It was an old 1950's wood console TV with the typical PTP wired steel chassis. After all it was the mid 60's and the older couple that lived there were not big spenders.
We were in one of the major flight paths for that AFB. Even though it was about 25 miles away military aircraft (from old C-47's to B-52's) were common sights in the skies over our house. Both my parents were air traffic controllers and my father was a WWII bomber pilot. He could tell you what the airplane was often without even seeing it. Yes, I could recognize a P-51 Mustang or the rare B-36 (six turning and 4 burning) by its sound.
There were a few neighbors who complained of broken windows from the booms.
What happens when somebody sticks a car body on a jet engine and runs it down a drag strip filled with people......It does make the Hooters girls dancing in the staging lanes scream and run for the building.
I guess that the sound of those cars and a few top fuel dragsters (louder than the jets) playing got the attention of one of the throttle jockeys at the Pratt and Whitney skunk works down the road (the track and Pratt are both located in way out in the swamp) to fly in low over the crowd, yank it back into a vertical stall and hit the afterburner. Just lighting that fireball makes a big bang followed by a loud roar and all we could see was a fireball in the sky since the jet was above it and going straight up.
Attachments
Indeed, though in my case it was 'weekend warriors' [Naval Air Reserves] supposedly practicing 'scrambling', etc..
June 1950, we've just moved into a new G.I. Tract home and while standing in front of a window fan the boom shattered the huge plate glass window next to me, sending a shard in between my left eye and eyebrow.
Fortunately, no real physical damage and the next door neighbor's wife had been a nurse in WWII, doing a great job patching me up to the point where the little scar is now 'lost' in a wrinkle.
Not too long later we would lose the replacement window before the military was forced to only do it in/on special occasions well away from any populated area. For whatever reason, none of the multiple small panes in the opening windows didn't break, though in retrospect assume their shoddy construction, poor materials, glazing putty like goo in the sweltering heat allowed them to absorb the shock.
GM
Derfy,
It is a point source but only 3 dB louder than if it was using one engine at the same power.
My question for you is what happens to you if a single engine plane has a takeoff engine failure?
As to breaking windows, the sound pressure would be pounds per square foot. So larger windows would see more energy! There is a reason to use tempered (safety) glass in larger windows.
It is a point source but only 3 dB louder than if it was using one engine at the same power.
My question for you is what happens to you if a single engine plane has a takeoff engine failure?
As to breaking windows, the sound pressure would be pounds per square foot. So larger windows would see more energy! There is a reason to use tempered (safety) glass in larger windows.
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You land.
Straight ahead of you,
Into the softest/smoothest area in front of you as slowly as possible.