Sound is a form of energy that travels as waves through the air, water or solids. When something vibrates (a guitar string, a speaker cone, your vocal cords), it pushes the air around it in a rhythmic pattern. The pattern travels outward, bumping into your ears, where it makes your eardrums vibrate. Your brain decodes that vibration as sound. Without something to vibrate through, sound cannot travel: which is why no one can hear an explosion in space.
- Speed in airAbout 343 m/sAt 20 C, sea level
- Speed in waterAbout 1,500 m/s4 times faster than air
- Speed in steelAbout 5,000 m/sEven faster
- Human hearing20 Hz to 20 kHzBats hear above 100 kHz
- DecibelsHow we measure loudnessWhisper 30, jet 140
- Sound in spaceCannot travelNo air to vibrate
What you will learn here
- What is a wave: the basic idea of waves.
- What is sound: how sound waves work.
- Frequency and pitch: why some sounds are high and others low.
- Amplitude and volume: what makes a sound loud or quiet.
- Echoes: sounds bouncing back to you.
- Ultrasound: sound too high for humans to hear, used in medicine and sonar.
- The sound barrier: when objects move faster than sound.
Why it matters
Sound is how we communicate (speech), express ourselves (music) and stay safe (alarms, warnings). It is also a powerful scientific tool: ultrasound scans show babies in the womb, sonar maps the ocean floor, and seismologists listen for the rumbles of earthquakes. Understanding waves goes beyond sound, too. Light, water ripples, earthquakes and radio signals are all waves, all sharing the same basic mathematics.