why can't aircraft that travel at supersonic speed be heard on the ground?

Answer 1

Most supersonic aircraft fly at high altitudes, for several reasons:
1) to avoid other, slower aircraft flying in the 30,000-45000 foot altitudes,
2) to minimize the effect on people and communities below, specifically because of the noise, and
3) to avoid geographical features -- when travelling at one to three times the speed of sound, slight changes in the craft's angle of flight can very quickly point one at the ground before you even realize anything has changed.

To address number 2, people on the ground would be able to hear a sonic boom if the plane flew low enough to the ground. However, when flying around 50,000 feet (over nine miles high), these planes are at sufficient distance that the sound waves dissipate before they reach the ground.

Answer 2

They ARE heard on the ground. Have you ever heard of a sonic boom?

You hear the aircraft LONG after the plane has passed because you see the plane when the light reflected off of the plane reaches your eyes at the speed of light, about 186 thousand miles per second. The sound of the plane reaches your ears at a much slower speed, so you hear it, after you see it.

Next time you get a chance, watch a carpenter hammer a nail. If you stand some distance away, the bang does not come to you at the same time you see the hammer strike.

Answer 3

Because they are moving faster than the "speed of sound" ..it's called breaking the "sound barrier"..So we hear it after the sound has happened..called a "sonic boom" Some aircraft break the sound barrier more than once..they are moving so fast. Then we will hear two sonic booms

This is worded very basically..there is a way more complicated scientific explanation.. but it's the same idea.

Answer 4

I thought it could only be heard on the ground by the "stationary and not in the plane since they are ahead of and faster than the "boom"
http://library.thinkquest.org/25486/english/supersonic/phenomena.shtml

Answer 5

They cause sonic booms which can be heard on the ground. They go faster than the sound they make.

Answer 6

Its because of the dopplar effect, when it passes the sound threshold, the waves become jumbled up behind the aircraft because its going faster than the sound. It happens to subsonic craft too.

Answer 7

Because they are traveling faster than the sound waves. So you won't hear the sound of the plane until it has already passed overhead.

Answer 8

They can, that's where the "Sonic Boom" comes from. Unless it's too high for the boom to be heard at ground level...

Answer 9

They can and are heard, but only well after they pass overhead. (sonic boom)

Answer 10

You can hear them. After they have passed.