Sound

Sound

What is Sound?

Sounds are vibrations
that we hear. Sound
travels in waves. Sound
waves are not like the
waves you see on the
water or the waves you
make by swinging a rope.
Sound travels in
compression waves.

Multiple Choice

Sounds are?

• air

• vibrations

• colors

Multiple Choice

Sound travels in

• steps

• points

• waves

• leaps

Can we see sound?

We think of sounds as what our
ears hear, but sounds are
actually vibrations. They exist
whether or not we hear them! But
what, exactly, is vibrating when a
sound is made?

Molecules, of course! Molecules
don't like to sit still. The
movement that starts these
vibrations in the molecules
causes sound. The vibrations
move away from the source of
the sound in waves, in the same
way light moves.

Multiple Choice

Do sounds exist if we do not hear them?

• Yes

• No

Multiple Choice

When a sound is made where do the molecules move?

• away from the sound

• towards the sound

• they do not move

Pitch

Sounds can travel through
the air, water, wood, or other
substances.

Sounds can be classified by
how low or high they are. This
is called the pitch of the sound.
The pitch is determined by
how fast the sound vibrations
move. Animals can hear
sounds at different pitches.

Multiple Choice

Sounds can travel through

• air

• water

• wood

• all of these

Open Ended

How high or low a sound is, is called the____?

Multiple Choice

Sounds that cause fast vibrations are at which type of pitch?

• high pitch

• low pitch

Multiple Choice

Sounds that cause slow vibrations are at which type of pitch?

• high pitch

• low pitch

Frequency

low-frequency sound wave. It has a
lower pitch. A wave that is vibrating very
fast has a high frequency and a higher
pitch.

Humans can hear sounds from a
frequency of about 20 vibrations per
second up to about 20,000 vibrations
per second. That's a wide range! These
units of frequency (vibrations per
second) are called hertz. When you
hear that a sound has 200 hertz, it
means the waves are vibrating 200
times each second.

Multiple Choice

Sound is measured in

• kilograms

• meters

• degrees

• hertz

Other animals have very different hearing
ranges. Dogs can hear sounds at much higher
frequencies than we can—well over 30,000
hertz! That's why some dog whistles and dog
fences use high-pitched sounds: The sounds
won't disturb people, but the dogs will respond.

Dolphins can make and sense sounds at
extremely high frequencies—about 150,000
hertz. Some whales give off low-frequency
sounds that can travel through the water for
hundreds of miles. Whales have extremely
sensitive ears that can sense these sounds
over long distances. Elephants can also use
very low-frequency sounds—much lower than
we can hear—to communicate with each
other!

Bats can make very high-pitched
sounds. These sounds are too high for
us to hear them, but they help the bats
find their way around.

Click the audio player below to hear a
recording of bat calls. These sounds
are ultrasonic, which means the bats
made them at frequencies that are too
high for us to hear them. This special
ultrasonic recording allows us to hear
these sounds.

Summary

Sounds are vibrations that travel in
waves. Sounds can be measured in
pitches and frequencies by how fast or
slow the molecules move away from
the sound.

Sound can travel through different
things such as water, wood and air.

Sound is measured in hertz and
different animals can hear sounds at
pitches that humans cannot hear.