Sonic Boom

fjmeat

Diamond Member
Jan 13, 2010
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Dopplereffectsourcemovingrightatmach1.4.gif


But the boom comes before the Jet passing over? Video: http://youtu.be/kMtjpDykp9k
 
Oct 25, 2006
11,036
11
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The video is probably not synced properly.

Also I'm not convinced that was a sonic boom. Jets are fucking loud and just because it CAN fly supersonic, doesn't mean it WAS flying supersonic.
 

Crusty

Lifer
Sep 30, 2001
12,684
2
81
Audio/video not synced up and that was definitely NOT a sonic boom.

If it was a sonic boom those car windows would have been shattered and those poor people's ears would probably be bleeding.
 

fjmeat

Diamond Member
Jan 13, 2010
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Audio/video not synced up and that was definitely NOT a sonic boom.

If it was a sonic boom those car windows would have been shattered and those poor people's ears would probably be bleeding.

My thought too. At the air show, the announcer always says the jets cant fly fast enough in a public area to create the boom. The crowd would go hysterical. But they can however, do it over the ocean. Won't that upset the shippers?
 

Jeffg010

Diamond Member
Feb 22, 2008
3,435
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I have been around 1 sonic boom and it was when I was fishing in MN. It sounded like an explosion. I never heard it again and I stayed whole summers on that lake. I don't know about shattering windows but it was pretty damn loud.
 

Crusty

Lifer
Sep 30, 2001
12,684
2
81
I have been around 1 sonic boom and it was when I was fishing in MN. It sounded like an explosion. I never heard it again and I stayed whole summers on that lake. I don't know about shattering windows but it was pretty damn loud.

At 50' in the air it would definitely shatter those windows.
 

Crusty

Lifer
Sep 30, 2001
12,684
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81

Every resource I've looked at puts sonic booms at 200+ decibels, some even say it approaches 215dB.

Ear drums rupture at less than 200dB and most glass breaks somewhere below 185dB.

At 50' in the air, like the plane was in the video, I stand by my statement saying that a sonic boom would shatter those windows and rupture their eardrums.
 

IronWing

No Lifer
Jul 20, 2001
73,058
34,323
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At the Oshkosh airshow they used to have a prop plane fly over that had propeller tips that would exceed the speed of sound such that it was continuously farting out little sonic booms. It was loud.
 

Train

Lifer
Jun 22, 2000
13,587
82
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www.bing.com
Every resource I've looked at puts sonic booms at 200+ decibels, some even say it approaches 215dB.

Ear drums rupture at less than 200dB and most glass breaks somewhere below 185dB.

At 50' in the air, like the plane was in the video, I stand by my statement saying that a sonic boom would shatter those windows and rupture their eardrums.

I think your estimates are way off. Myth busters had Blue Angels fly as low as possible and could barely break the weakest of glass. Car windows are one of the toughest forms of glass, they ain't gonna break due to noise. Else anyone who parks near a fireworks show would have their windows blown out.

And ears bleeding? GTFO
 

Crusty

Lifer
Sep 30, 2001
12,684
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I think your estimates are way off. Myth busters had Blue Angels fly as low as possible and could barely break the weakest of glass. Car windows are one of the toughest forms of glass, they ain't gonna break due to noise. Else anyone who parks near a fireworks show would have their windows blown out.

And ears bleeding? GTFO

Your car is a lot further away from fireworks shooting off than the car in the video is from the plane.

Did you even watch the video?

As far as the mythbusters episode goes... well it's mythbusters and their 'experiments' are hardly scientific.

Quote from the wiki page about the episode

Jamie set up a test area filled with various glass items and products while Adam performed a flyby in an F/A-18 going supersonic. However, at flybys of 8,000, 2,000, and 500 feet (2,400, 610, and 150 m), the jet failed to break any of the glass. They then performed a series of low altitude flybys at 200 feet (61 m), but only managed to break a single window. Since the majority of the glass was still intact, the MythBusters declared the myth busted.

That is at 200', the jet in the video is still lower than that.
 

boochi

Senior member
May 21, 2011
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That plane was probably only flying at around 200mph or a little over.
 

Train

Lifer
Jun 22, 2000
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Your car is a lot further away from fireworks shooting off than the car in the video is from the plane.

Did you even watch the video?

As far as the mythbusters episode goes... well it's mythbusters and their 'experiments' are hardly scientific.

Quote from the wiki page about the episode


That is at 200', the jet in the video is still lower than that.

Ok, so find me a sonic boom that DOES break a car window. We'll call that scientific.

Considering planes have been breaking the sound barrier for a good 70 or so years, you'd think there would be evidence of this.
 

Gibsons

Lifer
Aug 14, 2001
12,530
35
91
I think your estimates are way off. Myth busters had Blue Angels fly as low as possible and could barely break the weakest of glass. Car windows are one of the toughest forms of glass, they ain't gonna break due to noise. Else anyone who parks near a fireworks show would have their windows blown out.

And ears bleeding? GTFO

At low altitudes they probably aren't exceeding the speed of sound.
 

vshah

Lifer
Sep 20, 2003
19,003
24
81
Ok, so find me a sonic boom that DOES break a car window. We'll call that scientific.

Considering planes have been breaking the sound barrier for a good 70 or so years, you'd think there would be evidence of this.

breaking the sound barrier, yes. breaking the sound barrier at 50' above populated areas with glass to break? no.
 
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Crusty

Lifer
Sep 30, 2001
12,684
2
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Ok, so find me a sonic boom that DOES break a car window. We'll call that scientific.

Considering planes have been breaking the sound barrier for a good 70 or so years, you'd think there would be evidence of this.

You keep on ignoring the fact that this plane in the video is extremely close to the ground.

TBH I would be very surprised if there was ever a plane that broke the sound barrier at 50' in the air directly over a car, let alone just 50' in the air. I'm sure there would be quite a lot of stress on the plane.
 

Train

Lifer
Jun 22, 2000
13,587
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You keep on ignoring the fact that this plane in the video is extremely close to the ground.

TBH I would be very surprised if there was ever a plane that broke the sound barrier at 50' in the air directly over a car, let alone just 50' in the air. I'm sure there would be quite a lot of stress on the plane.

I'm not ignoring it at all, but even from 200 to 50 feet your not gaining many DB's on the ground. Interesting formula here: http://answers.yahoo.com/question/index?qid=20100306143514AAIt9hb

decibels on ground assuming 200 db boom:
200 - (20log(Height in Meters) + 11)

at 200 feet, you'd get 106.8 db, on the ground.

at 50 feet, you'd only have 134.5 db

Neither of which will put a crack in auto glass. Hell you can get car stereos to put out 150+
 

Gibsons

Lifer
Aug 14, 2001
12,530
35
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They were INTENTIONALLY exceeding the speed of sound.

It's not easy for any aircraft to get over M1 at 200'. Were they over it for the whole flyby, by how much?

Booms will vary a bit according to weather, type, size, speed of the aircraft. The window's susceptibility will vary depending on its properties as well as it's orientation to the boom, the surrounding land, etc.

I don't trust mythbusters at all.
 

Bubbaleone

Golden Member
Nov 20, 2011
1,803
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That's an old Sukhoi SU-24M "Fencer". Between 0:17 and 0:19 you can hear the man exclaim "Sukhoi". It's definitely subsonic as it looks to be traveling about 300-350mph. The sound is created by air being drawn into the large rectangular engine intakes at very high velocity, which for the relatively low speed he's traveling at would be extremely loud for several hundred yards in front of the aircraft.