Sound waves produced by an aircraft

[kent davidge]

Suppose that an aircfract somehow is not moving. Then I would expect the sound waves it produces to spread out uniformely in a spherical fashion. Now imagine a airplane traveling at approximately the speed of sound. In this case, if the airplane produces a wave at point A and after a time T the sound sphere has a radius R, then at R the airplane will produce another sound wave. The centre of this later sound sphere would always lie at the surface of the earlier sound sphere, because both are traveling at the same speed. The result in a time lapse would be like this

As opposed to this, an aircraft traveling at a lower than sound speed would draw a pattern like this

The main difference being that the two sphere surfaces don't "meet".

Now this reasoning is from my nearly zero understanding of waves.This is an attempt to explain sonic boom in simple terms. I did a previous search on web to find out whether this is correct or not, but didn't find any pictures like these above.

 

[ZapperZ]

Why do you think that, for the case of v<v_sound, that the airplane is at the center of the spherical wavefronts? The wavefronts are traveling at the speed of sound in air, but the aircraft is also moving in one direction. So it should be closer to the wavefront in front of it than the wavefront behind it.

And each subsequent wavefronts are not "concentric" with the previous wavefronts, because the center of the source of sound (the airplane) have moved.

Zz.

 

[kent davidge]

Why do you think that, for the case of v<v_sound, that the airplane is at the center of the spherical wavefronts? The wavefronts are traveling at the speed of sound in air, but the aircraft is also moving in one direction. So it should be closer to the wavefront in front of it than the wavefront behind it.

And each subsequent wavefronts are not "concentric" with the previous wavefronts, because the center of the source of sound (the airplane) have moved.

Zz.

Oh yea, I should have considered the displacement of the airplane.

 

[anorlunda]

Does this animation answer your question?

 

[kent davidge]

Does this animation answer your question?

It helps. How can we use it to explain the sonic boom?

 

[anorlunda]

Another picture may help. Note how the character of the wave front changes from spherical to conical as the airplane speed increases.

 

[phinds]

It helps. How can we use it to explain the sonic boom?

Have you done any research on your own regarding sonic booms? They are a well understood phenomenon and there is plenty of information available so I don't understand why you think it is necessary to try to create a new explanation.

 

[boneh3ad]

It helps. How can we use it to explain the sonic boom?

You can't, but you have independently stumbled across the well-known phenomenon known as a Mach angle.