Sound is a longitudinal wave that needs a medium to travel through. That’s why there’s no sound in space. Here are the key ideas for the Separate Physics sound topic.
How we hear
Sound waves make the ear drum vibrate, and those vibrations pass to other parts of the ear. This conversion into vibrations of solids only works over a limited range of frequencies, so humans can hear only from about 20 Hz to 20 kHz.
Pitch and loudness
- Higher frequency = higher pitch.
- Bigger amplitude = louder sound.
Echo calculations: don’t forget to halve!
You hear an echo from a cliff 1.2 s after clapping. Sound travels at 340 m/s. How far away is the cliff?
Distance = 340 × 1.2 = 408 m. But that’s there and back, so the cliff is 408 ÷ 2 = 204 m away.
Changing medium
When sound passes from air into water, it speeds up and its wavelength gets longer, but its frequency doesn’t change.
Leave a comment