Sonic boom Wave question

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In summary, the question on the test was asking for an example of an airplane traveling as fast as sound and creating a sonic boom. The correct answer given by the teacher was interference, but the student argued that it could also be Doppler effect. The teacher offered to give the student an extra point if they could provide a technical argument supporting the Doppler effect. The student explained that when standing in front of the airplane, the frequency is higher because the waves "pile" up, but when standing under the sonic boom, the frequency is lower because the waves are just going by. However, the teacher requested a more technical explanation. Another student suggested using the concept of constructive interference, which adds up the amplitudes of sound waves to produce
  • #1
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Ok, so basically the question on a test was if a a sonic boom occurs because an airplane travels as fast as sound what is it an example of. a) interference b) Doppler effect c) something else d) something else.

The correct answer which my teacher marked was interference, although I think it's doppler effect and my teacher was like if you can come up with an argument supporting that it's doppler effect he would give me the point back. Considering that my grade is an 87 and i still have 6 weeks to bring it up an A i still need the extra point cus it brings my grade up to an 88.

like this is how i explained it to him:

because when you're standing infront of the airplane the frequency is higher because the waves "pile" up, but when you're standing under the sonic boom the frequency is lower because the waves are just going by.

but my teacher needs a more "technical" argument. so can someone please help me with this.
 
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  • #2
Personally I'd go with constructive interference.

http://en.wikipedia.org/wiki/Sonic_boom

Remember no matter how hard Cinderella's stepsisters tried they couldn't get all their toes into the slipper.

Try looking at the other 12 things you got wrong if you want to mine a point.
 
  • #3
LowlyPion said:
Personally I'd go with constructive interference.

http://en.wikipedia.org/wiki/Sonic_boom

Remember no matter how hard Cinderella's stepsisters tried they couldn't get all their toes into the slipper.

Try looking at the other 12 things you got wrong if you want to mine a point.


That link doesn't provide any help.
 
  • #4
Hi iFat! :smile:
iFat said:
… when you're standing infront of the airplane the frequency is higher because the waves "pile" up, but when you're standing under the sonic boom the frequency is lower because the waves are just going by.

but my teacher needs a more "technical" argument …

Well, you try to word it technically :wink:

start with the three regions (I) in front of the boom (II) in the boom (III) behind the boom …

what do you say the Doppler effect is, and why, in each of those three regions? :smile:
 
  • #5
iFat said:
That link doesn't provide any help.

Not to your thesis any way.

The idea behind constructive interference in adding the amplitudes of the sound waves to produce the shock wave, is more closely related than any notion about increasing frequency as part of any Doppler effect.

I will admit that the question in not a sound one to begin with. But as one phenomenon - boom - is more related to a shock wave as opposed to the other being more a phenomenon of an increase in frequency ... don't call me as an expert witness in your case.

Perhaps your teacher will be impressed if you demonstrate a more in depth command of the matter?
 
  • #6
Does this work?

"I can see how it is constructive interference. Constructive interference is where the sound waves add up in order to produce a shock wave. But however since we didn't learn what a shock wave is, it is closely related to Doppler effect because as you are in front of the boom the waves add up making a higher pitch, and when you're in the middle of the boom the pitch of the boom stays constant, and when you're behind it, the frequency is lower which makes the pitch lower"
 
  • #7
iFat said:
in front of the boom the waves add up making a higher pitch

how?? why?

(in fact … i can't remember the answer to this … can the plane be heard at all in front of the boom?)
 
  • #8
tiny-tim said:
how?? why?

(in fact … i can't remember the answer to this … can the plane be heard at all in front of the boom?)

877005226.Ph.1.jpg


You see the picture to the farthest left. Like if you're behind the airplane, where the waves start adding up, there is more frequency where as when you're behind the airplane like farthest to the right it takes time for each wave to pass you which makes the frequency lower which makes the pitch lower. Right?
 
  • #9
tiny-tim said:
how?? why?

(in fact … i can't remember the answer to this … can the plane be heard at all in front of the boom?)

No. Your perception is of the trailing cone of the shockwave coming at some angle from the source. At higher Machs the wave is sharper to the direction of motion and may not even be heard on the ground as I recall.
 
  • #10
iFat said:
You see the picture to the farthest left. Like if you're behind the airplane, where the waves start adding up, there is more frequency where as when you're behind the airplane like farthest to the right it takes time for each wave to pass you which makes the frequency lower which makes the pitch lower. Right?

No. Give it up.

The middle picture exactly shows the more constructive interference nature of the phenomenon. Making a frequency argument is not compelling.
 
  • #11
I got my argument.

Thanks guys!

It doesn't hurt.
 

What is a Sonic Boom Wave?

A Sonic Boom Wave is a loud, explosive sound that occurs when an object travels through the air faster than the speed of sound. It is created by the buildup and release of pressure waves, similar to the shockwaves produced by an explosion.

How fast does an object need to travel to create a Sonic Boom Wave?

An object must travel at least at the speed of sound, which is approximately 767 miles per hour or 1,235 kilometers per hour. However, the speed of sound can vary depending on factors such as altitude and temperature.

What causes a Sonic Boom Wave?

A Sonic Boom Wave is caused by the sudden change in air pressure that occurs when an object travels faster than the speed of sound. As the object moves through the air, it creates a series of pressure waves that merge together and create a loud, explosive sound.

Can a Sonic Boom Wave be harmful?

No, a Sonic Boom Wave is not harmful to humans. However, it can be loud and startling, and may cause damage to nearby buildings or structures if the object creating the boom is flying too low.

Are Sonic Boom Waves only created by airplanes?

No, Sonic Boom Waves can also be created by other objects such as rockets, supersonic missiles, or even meteorites entering the Earth's atmosphere. However, airplanes are the most common source of Sonic Boom Waves.

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