Sonic Booms
When an object moves through stuff like water
or air, it creates a wave : energy spreads out.
When a moving object exceeds the speed of
waves in the medium it travels in, a disruption
occurs in the way energy spreads out from the
object.
High Pressure
Air is clear air
Low Pressure
Air is cloudy
air
Low pressure causes water
that’s in the air as a GAS to
condense into a liquid.
The water forms tiny
DROPLETS that are so small,
they float in the air : a cloud.
This photograph
shows variations in
air temperature.
These temperature
changes are related
to pressure changes
in the waves
around the jet.
Note the wave
AHEAD of the
jet….
Note the pressure wave as it hits the
water…
QuickTime™ and a
GIF decompressor
are needed to see this picture.
Here are 4
animations
showing the
waves rippling
out from an
object. Imagine
the center dot is
a bug on the
water, or a jet
moving through
the air.
This bug is not
moving…
QuickTime™ and a
GIF decompressor
are needed to see this picture.
This bug is
moving, but
more slowly
than the speed
of the waves.
Notice the
waves are
COMPRESSED
ahead, in the
direction of
movement, &
spread out, or
RARIFIED, in
the direction
opposite the
movement. This
accounts for the
DOPPLER
QuickTime™ and a
GIF decompressor
are needed to see this picture.
This bug is
moving at the
speed of the
wave. Notice
how the waves
are compressed
at the bow.
There’s a lot of
energy packed
into a very small
space directly in
front of the bug.
This accounts
for the great
difficulty in
going faster than
wave speed.
QuickTime™ and a
GIF decompressor
are needed to see this picture.
This bug is
SUPERSONIC,
Traveling faster
than the wave
speed. Notice
the trailing
“shockwave”.
This a sonic
boom, if the bug
is a jet, and the
wave is in air.
Flight at
supersonic
speeds is
relatively easy :
the hard part is
getting past that
compressed
Here’s a recording of a “sonic boom”. It’s from
pretty far away, so it’s not real loud. But you
should be able to get an idea of the tremendous
energy radiated away from the jet as it passes
through its bow wave and leaves its own sound
behind.
Quic kTime™ and a
Video decompressor
are needed to see this pic ture.
QuickTime™ and a
decompressor
are needed to see this picture.
Click on the picture to play the movie.
The jet is moving through pockets of air that
have more or less humidity, or may be slightly
warmer or colder. That’s why the clouds appear
and disappear.
QuickTime™ and a
decompressor
are needed to see this picture.
This car is a bit faster than the speed of sound.
The light area on either side of the car is created
when the bow wave interacts with the desert
“pavement” and raises a cloud of dust.
QuickTime™ and a
Intel Indeo® Video R3.2 decompressor
are needed to see this picture.
Going faster than the speed of sound on the
GROUND is more difficult than in the air, because
you have to contend with a highly reflective
surface (the ground) very close to that compressed
bow wave. Energy can’t escape.
This movie is
from a video
camera mounted
on the Thrust1, a
rocket car built to
exceed the speed
of sound. If you
listen closely, this
run does not go
supersonic, but
gets close. The
increasingly loud
sound represents
the build up of
sound wave
energy at the front
of the car.
Over the car, changes in air pressure & temperature
cause light to speed up or slow down, refracting (or
bending) as a result.