Sound

Sound is a form of energy that is all around us.

All sound energy is produced by vibrations.

Vibrations are a back-and-forth movement.

These vibrations move through matter. When there is no matter present for sound energy to move through (a vacuum), no sound is produced.

An example where there is no sound present: the moon

Explain why: Since there is no matter in space, or on the moon, sound energy has nothing to travel through. There are no air molecules present to vibrate back and forth.

Write two test questions using information found on this page! Write the answers, as well!

Q: _________________________________________________________

A: _________________________________________________________

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Musical instruments, such as string, woodwind, percussion, and brass instruments do two things:

(1) Vibrate

(2) Resonate

Resonance is the strengthening of a sound wave.

An example of resonance: You are at a football game, and you are cheering for your favorite team. You want the players to hear you so you use a megaphone. The sound the leaves your voice hits the walls of the empty cavity (the megaphone). The sound hits the walls of the megaphone and vibrates at the same speed as the sound waves inside the megaphone. The vibrating walls and the vibrating air molecules work together to strengthen the sound.

Write two test questions using information found on this page! Write the answers, as well!

Q: _________________________________________________________

A: _________________________________________________________

Q: _________________________________________________________

A:__________________________________________________________

List three things that we already know!

(1) Sound is a form of energy that is all around us.

(2) All sound energy is produced by vibrations (back-and-forth movements).

(3) All vibrating objects produce sound.

Experiment! Place your fingers on your windpipe. Explain what happens when you speak. You feel a vibrations because air is moving through the windpipe.

Draw a picture to show what happened!

Sound travels in compression waves.

A wave is a disturbance that moves through:

(1) solids (2) liquids and (3) gases

Compression is the part of the sound wave where the molecules of a sound wave are bunched up

Rarefractions are the areas of the sound wave that aren’t under pressure (not bunched)

Compression waves are made of compressions and rarefractions.

How is a slinky like a compression wave? When it is bunched up, it is like a compression, and when it is stretched, it is like a rarefraction.

Draw a picture that shows how a slinky is like a compression wave!

Sound waves have three different parts.

(1) Crest – Highest point of the sound wave

(2) Trough – Lowest point of the sound wave

(3) Wavelength – Distance between two side-by-side wave crests

Frequency & Pitch

For every sound you hear, some object is vibrating and producing

compression waves.

When an object vibrates quickly the number of

vibrations per minute increase,

so the sound becomes higher.

When an object vibrates slowly the number of

Vibrations per minute decrease,

so the sound becomes lower.

Frequency is the number of vibrations in a unit of time.

Pitch

Pitch is the highness or the lowness of the sound.

Objects that are larger and longer tend to vibrate slower than shorter smaller objects.

The slower the vibration, the lower the pitch.

The faster the vibration, the higher the pitch.

sounds higher than because: the instrument is is shorter and smaller, so it makes shorter vibratio vibrations.

The Speed of Sound

Sound is a form of energy that is produced by vibrating matter.

Where there is no matter, there is no sound.

Sound waves travel through matter.

The speed of a sound depends on the kind of matter it is moving through.

Of the three states of matter (gas, liquid, and solid) sound waves travel

* slowest through gases

* faster through liquids

* and fastest through solids

It takes longer for sound to travel through gas, because the molecules are spread

very far apart

For sound to travel through air, the floating molecules of matter must vibrate and

collide to form compression waves

Sound travels faster in liquids than in gases because the molecules are packed more

closely together.

This means that when the water molecules begin to vibrate, they quickly collide

with each other and quickly form a compression wave!

Sound travels over FOUR times faster through water than in air!

Sound travels fastest through solids because molecules in a solid are packed against

each other.

When a vibration begins, the molecules of a solid immediately collide and the

compression wave travels quickly!

Sound waves travel over SEVENTEEN times faster through steel than through air.

Sound is produced by vibrating objects.

Humans and other animals produce vibrations in many ways to communicate

Humans make sounds by moving our lungs across our vocal chords to produce

sound waves.

These sound waves create the sound we know as the human voice.

Other mammals that make sound this way include: dogs and bats!

Marine mammals, such as whales, make sound by passing air through air sacks

located in their heads to create sounds.

Hearing is the detection of sound

All animals detect sounds differently because different animals are able to hear

different frequencies of sound.

As you already know, sound is a form of energy produced by vibrating matter that

travels in waves called compression waves.

The frequency of sound is the number of vibrations in a unit of time.

The frequency of a sound gets higher when the wavelengths get shorter.

The frequency of a sound gets lower when the wavelengths get longer and the

number of vibrations decrease.

Because animals can hear sounds at different frequencies, some animals can hear

sounds that humans can’t hear. 

The sounds we hear best are sounds such as human conversation.

Our hearing is adapted to hear best the sounds we use every day!

Some animals like dogs, cats, mice, and bats can hear very high frequency sounds.

An example of when an animal hears a high pitch sound that we can’t hear is when:

You blow on a dog whistle or when you run the vacuum cleaner. These animals hear high frequency sounds that humans cannot hear!

Other animals like whales can hear very low frequency sounds. They use these sounds

that we can’t hear to communicate with other whales.