Book 14, Question 21
Why Do Sound Waves Push and Squeeze Instead of Going Up and Down?
Sound waves push and squeeze the air in the same direction the wave travels! That is different from water waves or a shaken rope. Scientists call sound a longitudinal wave.
More fun facts
- When a guitar string vibrates, a small part of its energy squeezes and stretches the air next to it, making slightly higher and lower pressures.
- The squeezed, high pressure parts are called compressions, and the stretched, low pressure parts are called rarefactions.
- These compressions and rarefactions move outward as a longitudinal wave with the same frequency as the string.
- Sound waves in air and most liquids are longitudinal because fluids have almost no shear strength, so they cannot pass along a side to side wiggle.
- In solids, sound waves can travel both as push and squeeze waves and as side to side waves.
- When the compressions and rarefactions travel up your ear canal, they push and pull on your eardrum and make it vibrate.
Questions kids ask
Why do sound waves fade away?
Some of their energy is soaked up by things they hit, like your eardrum, and some is turned into a tiny bit of heat in the air.
Do sound waves carry air with them?
No. The air only jiggles back and forth while the wave moves on.