Book 1, Question 112 · Video
Why Do Echoes Bounce? Sound Bounces Back Late!
Shout at a far wall and your voice comes back to you! Sound starts with vibrations and travels through the air in waves, and when a wave hits a hard surface it reflects, bouncing b
Read the full answer →What Crafty Clover says in this video
Intro
Hi! I'm Crafty Clover! Let's discover something amazing. Why do echoes bounce?
The Big Idea
Shout hello in a canyon, and hello, hello, comes back! That's an echo. An echo is your own sound, bouncing off a hard surface, and coming back to your ears. Let's see how it works, step by step!
Sound Is a Wave in Air
Step one: sound is a wave in air. When you shout, your voice box vibrates, and makes the air wiggle. Those wiggles spread out through the air in waves, like ripples on a pond.
A Hard Wall Sends the Wave Back
Step two: a hard wall sends the wave back. When the wave hits a hard surface, like a cliff or a brick wall, it reflects. That means it bounces back the way it came, like a ball bouncing off a wall!
You Hear the Bounce a Little Late
Step three: you hear the bounce a little late. The sound has to travel all the way to the wall, and back to you. That takes time! So first you hear yourself, and then, a moment later, the echo.
The Sound's Round Trip
Let's follow the sound's trip! Sound zooms through the air at about 340 meters every second. To hear a clear echo, the wall should be at least seventeen meters away. That's about as long as four cars! Any closer, and the echo blends right into your voice!
Quick Facts
Quick facts! Far walls make echoes come back later, because the sound travels farther. Soft things, like pillows and curtains, soak up sound, so they make weak echoes. Bats and dolphins use echoes to find food. That's called echolocation! And ships use echoes to measure how deep the ocean is!
Think Like a Scientist
Now, think like a scientist! Clap once in a tiled bathroom. Then clap once in a bedroom. What do you notice about the sound? Hard tiles bounce sound back, so the bathroom sounds echoey. Soft blankets soak it up! Which room is the best echo room?
Outro
Echoes bounce because sound waves reflect off hard surfaces, and come back to your ears a little late. Hello, hello, curious kids! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!