## Sonic Boom Explained - How is it Created - Animated Graphics

[Applause]

[Music]

many aircraft mostly military are

supersonic they can fly faster than

sound when they do they produce a sonic

boom

[Music]

we hear this boom before we hear the

noise of the airplane

what makes this sonic boom and why do we

hear the sound of the airplane only

afterwards sound expands in a sphere the

sound source produces vibrations which

travel in all directions as waves of

compressed air though the sound waves

move in three dimensions we can make it

clearer if we show them in to a white

circle we'll represent a single wave of

compressed air now here is the sound

source and here is the person who hears

the sound first the situation where the

sound source doesn't move the compressed

waves of air travel in regular

succession equally spaced the distance

between two compressions is called a

wavelength represented by this symbol

the Greek letter lambda this has shown

how the compressions expand when the

sound source stays in place but what

happens when the sound source is moving

will represent the speed of sound by the

letter C V stands for the speed of the

sound source let's see what happens when

the speed of the sound source is half

the speed of sound V equals one-half C

when the sound source moves the waves of

compressed air in front of the sound

source are closer together this means

that the wavelength here is shorter than

the wavelength of a stationary sound

source and behind the wavelength is

longer

now let's look at the picture when the

sound source moves at the same speed as

sound when V equals C

the compressed waves accumulate they

will all reach the observer at the same

time he hears a loud boom this time the

sound source will move faster than sound

at supersonic speed for our example we

will have it moved twice as fast let's

say that the observer is on the ground

below an aircraft the wave compressions

now form a cone

this is easier to see when we begin to

draw in more of the innumerable sound

waves that are actually generated the

more waves the more obvious the cone on

the surface of the cone the compressions

are very close to each other they

combine to form a percussion wave which

a person perceives as a very sharp

booming sound an airplane flying at

supersonic speed produces a conic

percussion wave which follows behind it

wherever the percussion wave hits the

ground the supersonic boom

can be heard now at the house on the

river now at the house near the woods

the percussion wave produces more than

just a loud startling sound it can break

windows so to avoid damage and annoyance

aircraft aren't allowed to fly low at

supersonic speeds over settled areas