Circuitmess Wacky Robot Hertz Instructions Manual page 11

In fact, sound travels faster through
denser materials than through air.
For example, sound travels about four
times faster in water than in air and
about 15 times faster in steel than
in air. This is why submarines use
sonar to detect objects underwater
and why doctors use ultrasound
to see inside the human body.
But how does sound travel
through these materials?
Well, just like in the air, sound travels
through vibrations. In water, these
vibrations cause the water molecules to
bump into each other, creating pressure
waves that travel through the water.
Sound travels even faster in solids like
metal and bone because the molecules
are packed closely together and can
pass the vibrations along quickly.