DESCRIPTION
What is sound?
Sound is vibration.
Vibration is a quick back-and-forth movement of particles.
A voice, drum, or guitar string makes sound when it vibrates.
particles moving back and forth = vibration
BOOK I · Meet Music
CHAPTER 01
BOOK I · Sound
CHAPTER 1 · Sound
DESCRIPTION
Sound waves
A vibration makes a sound wave.
The wave carries sound away from what is vibrating.
That is how a voice or instrument can reach your ears.
sound wave
DESCRIPTION
Amplitude
Amplitude is the size of the wave.
Bigger amplitude sounds louder. Smaller amplitude sounds softer.
We hear this every day. Turning the volume up makes a sound louder, while turning it down makes it softer—just like a yell compared with a whisper.
LOUDER
SOFTER
DESCRIPTION
Frequency
Frequency tells us how fast something vibrates.
Slower vibration gives us a lower pitch. Faster vibration gives us a higher pitch.
LOWER PITCH
stretched out
HIGHER PITCH
closer together
DESCRIPTION
How do instruments make sound?
Every instrument begins with vibration.
What vibrates is different from instrument to instrument.
STRING
PERCUSSION
PIANO
DESCRIPTION
Strings
A string makes sound when it vibrates.
It can be plucked, bowed, or struck.
Guitar, violin, harp, and piano all use vibrating strings.
DESCRIPTION
Air
Wind and brass instruments use a vibrating column of air.
The player starts the vibration by blowing.
Flute, clarinet, trumpet, and trombone all use vibrating air.
DESCRIPTION
Percussion
Percussion instruments make sound when part of the instrument vibrates after it is struck, shaken, or scraped.
A cymbal vibrates after it is struck. Drums, bells, and xylophone bars vibrate too.
DESCRIPTION
How does a piano make sound?
A piano uses a key, a metal action rod, a felt-covered end, a string, and a damper.
When you press the key, the metal rod moves upward. The felt-covered end reaches the string from underneath, and the string vibrates.
The damper lifts away while the note sounds, then returns to stop the string from vibrating.
EXPLORE
See what vibrates
Choose an instrument family.
APPLICATION
What family is the cello from?
CELLO
Choose one family.
APPLICATION
What family is the saxophone from?
SAXOPHONE
Choose one family.
APPLICATION
What family is the tambourine from?
TAMBOURINE
Choose one family.
REVIEW
What did we discover?
CHAPTER COMPLETE
You explored how instruments make sound.
Different instruments vibrate in different ways, but vibration is the beginning of every sound.
stringsairpercussionpiano
EXPLORE
Change the wave
This graph is a representation of changing pressure over time. The air itself is not moving through space in this wavy shape; air particles oscillate back and forth while the disturbance travels onward.
Frequency controls how many cycles fit into the same time.
Amplitude controls the height of the graph.
APPLICATION
Watch a sound wave travel
Press the wave and watch the vibration travel outward.
APPLICATION
Change the amplitude
Choose an amplitude level and compare how the wave and volume change.
MEDIUM
Medium amplitude makes a medium-sized wave and a medium-volume sound.
APPLICATION
Change the frequency
Choose a lower or higher frequency. The amplitude stays the same while the wave gets more spread out or closer together.
LOWER PITCH
Lower frequency means slower vibration and a lower pitch.
REVIEW
What did we discover?
CHAPTER COMPLETE
You have explored sound.
You followed sound from vibration into a traveling wave and explored how frequency and amplitude change what you hear.
vibrationsound waveamplitudevolumefrequencypitch
DESCRIPTION
How does sound get from here to there?
Sound travels through matter.
A vibration begins at a source, then nearby particles pass that vibration along.
EXPLORE
The particles do not travel to your ear
Each particle moves only a little, bumping the next particle and passing the vibration onward.
The energy travels. The particles stay near their own place.
EXPLORE
Sound needs something to travel through
Sound can move through gases, liquids, and solids because all three contain particles that can pass vibration along.
AIR
gas
Particles are spread farther apart, but they still pass the vibration along.
WATER
liquid
Particles are closer together and can pass vibration through the liquid.
WOOD
solid
Particles are packed closely together, so vibration can pass from one to the next.
APPLICATION
What about empty space?
Sound needs matter to travel. But what happens when there is little or no matter at all?
Scientists call a space with little or no matter a vacuum.
VIBRATION
VACUUM
space with little or no matter
Outer space is nearly a vacuum, so there are not enough nearby particles to carry ordinary sound.
In a vacuum, sound cannot travel.
REVIEW
What did we discover?
CHAPTER COMPLETE
Sound made the journey.
A vibration began at its source, traveled through matter, and reached a listener.
sourceparticlesmattervibrationvacuum
DESCRIPTION
How does a vibration become something you hear?
Hearing is a chain reaction.
Sound reaches the ear as vibration. Different parts of the ear collect it, transfer it, change it into nerve signals, and send those signals to the brain.
EARcollects sound
→
VIBRATIONmoves inward
SIGNALtravels by nerve
→
HEARINGsound is recognized
EXPLORE
The outer ear collects sound
The visible part of your ear is the pinna. Its shape helps collect sound waves and guide them into the ear canal.
EAR CANAL
EXPLORE
The eardrum begins to vibrate
At the end of the ear canal is a thin membrane called the eardrum, or tympanic membrane. When sound reaches it, the membrane vibrates back and forth.
EARDRUM
tympanic membrane
EXPLORE
Three tiny bones pass the vibration along
Behind the eardrum is the middle ear. It contains the three smallest bones in the human body: the malleus, incus, and stapes.
Together, these bones are called the ossicles. They transfer the eardrum's vibration deeper into the ear.
VIBRATION→EARDRUM→
MALLEUS→INCUS (anvil)→
STAPES→INNER EAR
EXPLORE
Inside the cochlea, movement becomes a nerve signal
The cochlea is a fluid-filled structure in the inner ear. Vibration entering the cochlea creates movement in its fluid.
Inside are specialized hair cells. Their tiny hair-like structures bend with the movement and help convert mechanical vibration into electrical signals.
APPLICATION
Your ear detects it. Your brain recognizes it.
The electrical signals leave the inner ear through the auditory nerve and travel to the brain.
The brain processes those signals so you can recognize what you are hearing—such as a voice, a piano note, or a sudden clap.
COCHLEA
creates electrical signals
AUDITORY NERVE
carries the signals
BRAIN
recognizes the sound
mechanical vibration→
electrical signal→
recognized sound
REVIEW
What did we discover?
CHAPTER COMPLETE
Now you know how we hear sound.
A vibration entered the ear, moved through its structures, became a nerve signal, and was processed by the brain.
pinnaeardrumossiclescochleaauditory nervebrain
HIGH & LOW SOUNDS
Pitch is the height of a sound.
Some sounds feel high. Others feel low.
Frequency is the scientific term for how often a vibration repeats. We measure frequency in hertz (Hz). Faster vibrations have a higher frequency and we hear them as a higher pitch; slower vibrations have a lower frequency and we hear them as a lower pitch.
That quality is called pitch. A bird's chirp may sound high, while a large drum or low piano note may sound low.
Pitch does not tell us how loud a sound is. It tells us where the sound seems to sit from low to high.
LOW PITCH
lower, broader wave
HIGH PITCH
higher, closer wave
VIBRATION SPEED
Faster vibrations make higher pitches.
Remember frequency from Chapter 1? Frequency is how quickly a vibration repeats.
When the vibration repeats slowly, we hear a lower pitch. When it repeats more quickly, we hear a higher pitch.
LOWER PITCHstretched out
HIGHER PITCHcloser together
EXPLORE
What makes a string sound higher or lower?
A vibrating string can change pitch. Shorter vibrating lengths tend to vibrate faster and sound higher; longer vibrating lengths tend to vibrate more slowly and sound lower.
This is one reason string players change the vibrating length of a string with their fingers.
COMPARE
High and low can happen on many instruments.
Pitch is not tied to one instrument. Voices, strings, winds, percussion, and keyboards can all produce pitches at different heights.
Listen for the direction: does the sound move higher, lower, or stay about the same?
1 / 4
LOOK + LISTEN
Is this sound wave showing a high or low pitch?
Look at the wave, listen, then choose.
MUSICAL DIRECTION
Pitch can move up, down, or repeat.
Once we can hear high and low, we can follow the direction of pitches in music.
A sequence can rise toward higher sounds, fall toward lower sounds, or repeat at the same pitch.
Choose a direction to see and hear the notes.
REVIEW
What did we discover?
CHAPTER COMPLETE
Now you can follow pitch from low to high.
You connected what you hear to vibration speed and learned to recognize the direction of pitch.
pitchlowhighvibration speedvibrating lengthdirection
DESCRIPTION
Amplitude
Amplitude describes the size of a vibration or sound wave.
When a vibration moves only a small distance from its resting position, it has a smaller amplitude.
When it moves farther from its resting position, it has a larger amplitude.
We can hear this difference: smaller amplitudes usually sound softer, while larger amplitudes usually sound louder.
SMALLER AMPLITUDEsofter sound
LARGER AMPLITUDElouder sound
EXPLORE
Amplitude measures how far the vibration moves.
The middle line is the vibration's resting position. Amplitude measures the distance from that resting position to the greatest displacement.
Press each example to watch the same vibration move by a different amount.
LISTEN
Amplitude changes loudness—not pitch.
The frequency can stay exactly the same while the amplitude changes.
That means the pitch stays the same, but the sound becomes softer or louder.
Press each wave and compare.
MUSIC CONNECTION
Musicians shape loud and soft sounds.
Amplitude is the physical measurement. Loudness is what we perceive when we hear the sound.
Musicians use changes in loudness to create contrast, direction, and expression.
In music, changes in loudness are part of dynamics — the way musicians shape softer and louder sounds for expression.
Crescendo: the sound gradually grows louder.
Decrescendo: the sound gradually grows softer.
APPLICATION
Compare amplitude and loudness.
Each example may ask about amplitude or how the sound is heard. Look at the waves, then press the animation that best answers the question.
1 / 4
Which wave has the larger amplitude?
Press the wave that best answers the question.
REVIEW
What did we discover?
CHAPTER COMPLETE
Now you can see and hear amplitude.
You connected the size of a vibration to the way we experience sounds as louder and softer.
amplitudevibration sizeloudersofterfrequencyloudness
DESCRIPTION
Timbre
Timbre is the unique quality or character of a sound.
It is what helps your ears tell one instrument or voice from another—even when they are making the same pitch at a similar volume.
Same note. Similar volume. Different sound.
EXPLORE
Same pitch. Different timbre.
Listen to the same C played with four different sound characters.
PITCH sameVOLUME similarTIMBRE different
Press each instrument. What stays the same? What changes?
EXPLORE
Sounds have different characters.
Timbre gives a sound its own character. These abstract sounds are not meant to be recognizable instruments—listen only to the quality of each sound.
Press a sound character to hear an example.
These words help us describe timbre. They are not fixed labels—different listeners may describe a sound in different ways.
APPLICATION
Which timbre do you hear?
Listen, then choose the instrument you recognize.
1 / 4
Hear the sound, then choose.
APPLICATION
Same timbre or different timbre?
Pitch may change. Listen for the character of the sound.
1 / 4
A → B
Hear both sounds, then compare their timbre.
REVIEW
What changed?
Choose whether the example describes a change in pitch, volume, or timbre.
1 / 4
Choose what changed.
REVIEW
What to remember about timbre
CHAPTER COMPLETE
Now you can recognize timbre.
You heard how different instruments and voices can have their own recognizable sound—even when pitch and volume stay the same.
timbresound qualitysound characterinstrument recognitionsame pitchdifferent timbre
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