Contrasts with
LightBoth travel as waves and carry energy, but light needs no material and races a million times faster than sound.
Sound
Why does a drum you cannot touch still reach your ears?
Sound is a vibration travelling through air, water and solids. Learn what makes a sound high or low, loud or soft, why space is silent, and how your ears turn shaking air into music.
5 depths≈ 195 min of reading76 practice questions
The ladder
Choose how deep to go
Every depth is open. Start where it feels interesting — you can always move back.
- Discoverabout 30 minEverything that sounds is shakingFeel your own throat buzz, watch a tuning fork throw water, and follow the shaking from a tabla skin across the room to the hair cells in your ear. Meet pitch, loudness, echoes and the thunder rule, and find out why nothing at all can be heard in space.Owner-accepted · not line-by-line reviewed
- Understandabout 40 minCompressions, rarefactions and the wave equationSee what a sound wave actually is: a train of squashed and stretched air marching outwards. Meet longitudinal waves on a slinky, the equation v = f × λ, why steel beats air by seventeen times, how decibels multiply, and the engineering of the human ear.Owner-accepted · not line-by-line reviewed
- Investigateabout 35 minPredict it, try it: resonance, echoes and everyday sound technologyPush a swing at the wrong rhythm, make a wine glass sing, and find the sympathetic strings that ring inside a sitar untouched. Time an echo the way sonar and a hospital scanner do, compare a bat's call with a dolphin's, and see why India's noise rules are stricter near a hospital than in a market.Owner-accepted · not line-by-line reviewed
- Go deeperabout 45 minWhy resonance, harmonics and reverberation work the way they doFind out why resonance cannot grow forever, why two famous bridge wobbles had different causes, and why 56 granite pillars at Hampi ring with different notes. Meet Wallace Sabine, who found the reverberation formula with borrowed cushions, and the arithmetic of combining decibels.Owner-accepted · not line-by-line reviewed
- Extendabout 45 minDoppler shifts, digital recording and listening to the EarthWork out how much a siren's pitch shifts as it passes, find out why your recorded voice sounds strange (a real anatomical reason), and see why 44,100 Hz was not an arbitrary choice. Try two projects, solve combined puzzles, and use sound's own reasoning to locate an earthquake.Owner-accepted · not line-by-line reviewed
Practise and apply
Question bank · 76 questions
9 sections from Foundation to Challenge, each with hints and a worked solution — or play a 10-question round for points and stars.
Foundation 16Core 33Stretch 18Challenge 9
The web
Connected ideas
Follow a connection when you’re curious — some lead into completely different areas.
Sound
Used inanother area
Anatomy of the human bodyThe ear turns shaking air into signals a nerve can carry: a drum, three tiny bones and a spiral of fluid.
Words to know
59 words are explained in these lessons
VibrationSourceMediumVacuumFrequencyHertz (Hz)PitchAmplitudeLoudnessDecibel (dB)EchoEardrum+47 more