How Sound Waves Travel

Science · Waves, Light & Sound · ages 11-12

Name ______________________ Date ____________

Sound travels at different speeds through different materials. Through which material does sound travel fastest?
- Air
- Water
- Steel
- It travels at the same speed everywhere
When a guitar string vibrates, what does it push and pull in the air around it?
- Regions of compression and rarefaction
- A magnetic field
- Bright light waves
What is an echo?
- A sound wave that gets absorbed and disappears
- A sound wave that bounces off a hard surface and returns to your ear
- A sound wave that changes into heat
Sound can travel through the empty vacuum of space the same way it travels through air.
Circle one: True False
On a hot summer day, the air particles move faster and bump into each other more easily than on a cold day. What happens to the speed of sound in air on a hot day?
- Sound travels faster
- Sound travels slower
- The speed stays exactly the same
- Sound stops completely
Sound travels through air at about 343 meters per second. If you shout and the sound travels for 3 seconds, about how many meters does it go?
Answer: ______________
A ship uses sonar to find a submarine underwater. How does sonar work?
- It shines a light and measures the color that bounces back
- It sends out a sound wave and times how long the echo takes to return
- It listens only for the submarine's engine vibrations
Look at the bar chart comparing sound speed in different materials. Which material lets sound travel fastest?
- Liquid
- Gas
- Solid
Priya claps once in an empty, tiled gym and hears a clear echo. She then hangs thick curtains and mats over the walls and claps again in the same spot. What most likely happens to the echo?
- It becomes quieter or disappears because the soft materials absorb the sound
- It turns into an echo of light instead of sound
- It becomes louder because soft materials reflect more sound
Amir says, 'If an astronaut shouted during a spacewalk, another astronaut floating nearby could hear it directly through space.' What is wrong with Amir's claim?
- Astronauts' voices become too quiet in space to make any sound wave
- Sound waves can only travel at night, and spacewalks happen during the day
- Space is a vacuum with no particles, so a sound wave can't travel through it

Answer key

For grown-ups. Fold this page away before handing over the rest.

How Sound Waves Travel W1-mt_DQk9oDE7gr-s1

Steel · Sound is a vibration that passes from particle to particle. In a solid like steel the particles are packed tightly together, so the vibration passes along fastest. It moves slower in water and slowest in air.
Regions of compression and rarefaction · The vibrating string squeezes air particles together (compression) and spreads them apart (rarefaction), and that pattern travels outward as sound.
A sound wave that bounces off a hard surface and returns to your ear · An echo happens when a sound wave reflects off a hard surface, like a wall, and travels back to your ear.
False · A vacuum has no particles to compress or pull apart, so a sound wave can't form there at all.
Sound travels faster · Warmer air particles move around faster, so they pass the vibration along more quickly. That is why sound travels a bit faster through warm air than through cold air.
1029 · Speed tells you how far something goes each second. Multiply the speed of sound by the number of seconds: 343 x 3 = 1029 meters.
It sends out a sound wave and times how long the echo takes to return · Sonar sends a sound wave toward an object and measures how long the echo takes to come back, which shows how far away the object is.
Solid · In solids, particles are packed tightly together, so each one passes the vibration to its neighbor very quickly.
It becomes quieter or disappears because the soft materials absorb the sound · Soft materials absorb sound energy instead of reflecting it, so covering hard surfaces reduces echoes.
Space is a vacuum with no particles, so a sound wave can't travel through it · Sound needs particles to compress and stretch. Since space is a vacuum, there is nothing there to carry a sound wave.