Sound Is Made by Things Vibrating
Atlas stands in a school music room, plucking a guitar string with one finger while the string visibly wobbles back and forth, his other hand held near the string to feel the tiny movements in the air
- Explain that sound is made when an object vibrates back and forth quickly
- Identify vibrations in everyday objects that make sound, such as a drum, a guitar string, and a speaker
- Predict whether a stretched rubber band will make a sound when plucked and explain why
- Compare a loud sound to a quiet sound in terms of how much the object is vibrating
Key terms
- vibration
- a fast back-and-forth movement
- sound
- what you hear when something vibrates
- eardrum
- a thin flap inside your ear that vibrates
- loud
- a strong sound from big vibrations
Sound Starts With Shaking
Every sound in the world is made when something vibrates, which means it moves back and forth very fast. Put your fingers on your throat and hum, and you can feel your voice box shaking. When you pluck a guitar string, it wobbles so fast that it looks blurry. Those quick back-and-forth movements push and squeeze the air around them. If nothing is vibrating, there is no sound at all to hear.
Sound Travels to Your Ear
The squeezes in the air travel like tiny invisible ripples all the way to your ear. Inside your ear, a thin flap called the eardrum starts to vibrate too. Your brain turns that shaking into the sound you hear. Big, strong vibrations make a loud sound, and small, gentle vibrations make a quiet sound. Sound can travel through solids, liquids, and air, which is why you can sometimes hear music right through a wall.
Worked examples
You pluck a guitar string, then press it to stop it moving. What happens to the sound?
- The plucked string vibrates back and forth to make sound.
- Pressing the string stops it from vibrating.
- With no vibration, the air is no longer pushed.
Answer: The sound stops because the vibration stops.
You tap a table lightly, then tap it much harder. Which tap is louder?
- Tapping makes the table vibrate back and forth.
- A harder tap makes the table vibrate more strongly.
- Bigger, stronger vibrations make a louder sound.
Answer: The harder tap is louder because it makes bigger vibrations.
Activity
Sort each object into the correct bin — does it make sound by vibrating?
Practice
Name two things that make sound by vibrating back and forth.
Explain why a louder drum tap makes the drum skin vibrate more.
Common mistakes to avoid
- air makes sound on its ownA vibrating object pushes the air first; air does not move alone.
- a still rock can make soundSomething must vibrate to make sound, so a still rock stays silent.
Check your understanding
What must happen to an object for it to make a sound?
You pluck a guitar string and hear a note. Then you press the string to stop it from moving. What happens to the sound?
A student says, 'Sound is made by air moving on its own, not by the object.' What is wrong with this idea?
Recap
Sound is made when something vibrates, moving back and forth very fast. Those vibrations push the air into ripples that travel to your ear and shake your eardrum. Big vibrations make loud sounds, small ones make quiet sounds, and no vibration means no sound.
Reflect
What sound did you hear today, and what was vibrating to make it?