# Sound waves

• September 1st, 2017, 05:14 AM
geordief
Sound waves
Suppose we have an aircraft flying East to West and at a steady altitude (just for the sake of setting the scene).

If it is traveling at below the speed of sound will the sound waves from the plane reach all equidistant observers at the exact same time if there is no movement in the air mass and the density of the air mass is the same in all directions (etc etc) ?

So an observer ahead of the path of the aircraft will hear the sound (receive the sound wave) with the same delay as an equidistant observer behind the aircraft..... ?

Does the situation change at all if the aircraft is traveling at supersonic speeds?
• September 1st, 2017, 11:30 AM
Janus
If the observers are stationary with respect to the air mass, then any sound emitted by the plane at the moment it is halfway between the observers will arrive at both observers a the same time.
If the observers are moving with the aircraft and maintaining a equal distance from the Aircraft, then the any sound emitted will reach the trailing observer before reaching the leading observer.
• September 1st, 2017, 12:33 PM
geordief
Quote:

Originally Posted by Janus
If the observers are stationary with respect to the air mass, then any sound emitted by the plane at the moment it is halfway between the observers will arrive at both observers a the same time.
If the observers are moving with the aircraft and maintaining a equal distance from the Aircraft, then the any sound emitted will reach the trailing observer before reaching the leading observer.

In the first case is this still true if the plane travels at a supersonic speed?(I assume it is)

In the second case is this scenario identical to one where all three (the two observers and the plane ) are stationary but the air mass is moving?