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Author Topic: If I fly along behind a plane going faster than sound, what do I hear?  (Read 8833 times)

Offline chris

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If I fly behind an aeroplane that's travelling faster than the speed of sound, what do I hear (assuming that I can listen to what's going on outside my plane)?

Chris


 

Offline Flyberius

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Whtever it is, I imagine it is extremely loud.
 

Offline LeeE

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Interesting question

I'm not sure you'd hear anything because I think the sound wave from the 'boom' will be standing still relative to the aircraft.  Assuming you're maintaining the same speed as the aircraft you're following and neither of you are accelerating/deccelerating, you'd be located in the same part of the wave, traveling along with it, and sitting in a constant pressure region.
 

Offline DoctorBeaver

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The "boom" is being constantly produced by a plane traveling at supersonic speed, and it spreads out in a cone to the rear (the "boom forest"). Therefore, If you were travelling at the right distance behind and the right angle perpendicularly to be on the edge of the cone, wouldn't you hear a constant boom?
 

Offline Karen W.

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Interesting question

I'm not sure you'd hear anything because I think the sound wave from the 'boom' will be standing still relative to the aircraft.  Assuming you're maintaining the same speed as the aircraft you're following and neither of you are accelerating/deccelerating, you'd be located in the same part of the wave, traveling along with it, and sitting in a constant pressure region.

 I tend to agree with lee you would hear nothing.. because you are traveling the same speed and the sound I would think from both of you would be traveling backwards past you both neither I would think would hear it..
 

Offline Freeman

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Interesting question

I'm not sure you'd hear anything because I think the sound wave from the 'boom' will be standing still relative to the aircraft.  Assuming you're maintaining the same speed as the aircraft you're following and neither of you are accelerating/deccelerating, you'd be located in the same part of the wave, traveling along with it, and sitting in a constant pressure region.

 I tend to agree with lee you would hear nothing.. because you are traveling the same speed and the sound I would think from both of you would be traveling backwards past you both neither I would think would hear it..

Yes but isn't that just the sound barrier as viewing it from a spectators point of view.As I have it while you are actively engaged behind the aircraft in front you would fly into the deafening sound the jet engines kick out at full power being that you are the first to be hit by it relatively speaking.
 

Offline yor_on

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No you won't, those planes do leave the sound behind them.
Inside a plane is a different question as it is isolated from the airwaves surrounding the planes frame.
http://www.interesting.vaty.net/2006/09/breaking-sound-barrier.html
http://www.strategypage.com/military_photos/military_photos_200411122.aspx


To know the actual 'barrier speed' you need to know the temperature as well as the airs mixture.
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/souspe.html
http://en.wikipedia.org/wiki/Sonic_boom
« Last Edit: 10/01/2009 22:51:32 by yor_on »
 

Offline DoctorBeaver

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There is an interesting story associated with breaking the sound barrier.

The British knew in 1943, while they were developing the Miles M52 supersonic aircraft, that an all-moving tailplane was essential or turbulence would cause the aircraft to become too unstable. In 1944 the new labour government decided to cancel the project just weeks before the M52 was due to fly and as a result our research data was passed to the Americans who had been struggling (nothing new there) to solve the turbulence problem. The Americans consequently built the X1 and it did indeed break the sound barrier.

Some time later the test pilot for the now-abandoned M52 project was invited to America to fly the X1. This he did and just for a laugh caused the sonic boom to occur over the airfield. The percussion wave broke all the windows in the base commander's greenhouse.  :D

Incidentally, a scaled-down model of the M52 broke the sound barrier a while later and it was calculated that the full-size version would have flown at 1,000mph - considerably faster than the X1.
 

Offline LeeE

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Yes, in many ways the M-52 was more advanced than the Bell X-1.
 

Offline DoctorBeaver

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LeeE - indeed it was. Unfortunately, as has happened so many times in aviation, we Brits have designed world-beating aircraft only to have the financial plug pulled. A classic case in point was the TSR-2; by far the most advanced strike aircraft in the world at the time.
 

lyner

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The 'BOOM' is a shock wave. If you were to fly close to or 'in' it, I think you would experience a lot of buffeting - a bit analogous to riding the bow wave of a large ship. Because your relative speed is the same as the wave, the frequency would be zero, so no Boom.
 

Offline LeeE

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Yup - as I said earlier, the shock wave is traveling with the aircraft and is stationary relative to it.  If your aircraft is stationary relative to the aircraft you're following then you're also stationary relative to the shock wave and sitting in a constant pressure zone, so no frequency, and no boom.
 

lyner

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but lots of disturbance / buffeting and, of course, you're producing your own shockwave.
 

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