Physics · KS3 Y9 · Waves (Light & Sound)

Echoes and the speed of sound

Echoes and the speed of soundFree3:18Heddy Score 3 of 7, below the standard

What you need to know

  • The speed of sound depends on the material it travels through.
  • Stiffer materials carry sound faster, while denser materials tend to slow it down.
  • Sound travels about 14 times faster in iron than in air, so it is usually fastest in solids, slower in liquids and slowest in gases.
  • In air, sound travels at about 343 m/s at 20 °C, and a little faster when the air is warmer.
Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

303K views · 2.02K likes · khanacademymedicine 1.92M subscribers

As reported by YouTube on 2026-11-02. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

Explains why sound travels at different speeds in solids, liquids and gases, and gives the speed in air.

khanacademymedicine on YouTubechecked 2026-10-22

Plays from youtube-nocookie.com. No YouTube cookies until you press play.