Breaking The Barrier:)

http://www.scientificamerican.com/article/what-happens-when-an-airc/   (simplified)

What happens when an aircraft breaks the sound barrier?

Mar 11, 2002.

What happens when an object breaks the sound barrier must begin with the description of sound as a wave.  Anyone who has heard an echo (sound waves reflecting off a distant surface) or been far enough away from an event to see it first and then hear it, is familiar with the reasonably slow travel of sound waves. At sea level and temperatures of 22 degrees Celsius, sound waves travel at 345 meters per second. As the temperature decreases, the sound speed also decreases, so for a plane flying at 35,000 feet (10688 metres) where the temperature is  around -55 degrees Celsius, the speed of sound is 295 meters per second.

When the sources of a sound is moving it can begin to catch up with the sound waves they emit. As the speed of the object increases to the speed or velocity of sound waves, these sound waves begin to pile up in front of the object. If the object has sufficient acceleration, it can burst through this barrier of sound waves and move ahead of the sound it is making. As the object outruns all the pressure and sound waves in front of it, it is heard on the ground as an explosion, or sonic boom.

At supersonic speeds (those greater than the speed of sound), there is no sound heard as an object approaches an observer because the object is traveling faster than the sound it produces. Only after the object has passed will the observer be able to hear the sound waves emitted from the object.

Aircraft wings create low-pressure regions. Under sonic flight conditions the lowered pressure condenses the water in the air, creating a vapour cloud. Just as the aircraft bursts through the sound barrier, the air is locally disturbed by the resulting shock wave and the condensation/vapour cloud disappears.

Explain how there can be slight variation in the speed of sound? In hot temperatures, sound travels travels at 345 metres per second but in cold temperatures, sound travels in a different speed which is 295 metres per second.

What is an echo? An echo is sound waves reflecting off a distant surface and then travels back to the listener.

What happens to the sound waves, when the object making the sound is moving? The sound waves begin to pile up in front of the object.

Why is there no sound heard as an object approaches if it is going at supersonic speed?

Because the object is moving faster than the sound it produces.

What does supersonic mean? Supersonic is those greater than the speed of sound.

What does decrease mean? Decrease means to make or become smaller or fewer in size, amount, intensity or degree.

Sufficient? Private income.

Emit? Gas or radiation.

Velocity? A speed of something in a given direction.

Condense? Something density or more concentrated.

Acceleration? A vehicle capacity to gain speed.