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Invisible Pressure Waves Around You
📖 Invisible Pressure Waves Around You
Right now, every sound you hear is actually air being repeatedly squeezed and stretched. When someone speaks, their vocal cords vibrate, pushing air molecules together (compressions) and apart (rarefactions). This ripple of pressure differences travels outward at 330 m/s and enters your ear canal, vibrating your eardrum — and your brain interprets that vibration as sound. Bats navigate by sending out ultrasound pulses and listening for the echoes bouncing back from insects and walls. Doctors use the same principle with ultrasound scanners to see inside your body without any surgery!
Sound as a Longitudinal Wave
Sound is a longitudinal wave — air molecules vibrate back and forth in the same direction as the wave travels. This creates alternating regions:
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🧠 Memory Aid
Sound speed order: "Sounds Go Louder Solidly" — Gas (slowest), Liquid, Solid (fastest). Or remember: denser and more rigid = faster.
Sound wave trace — what changes what:
- Amplitude = how tAll the wave is = how Loud (A and L both go together)
- Frequency = how Frequently packed the waves are = Pitch (F and P both go together)
Echo distance formula: "Half the time, all the distance" — divide the total time by 2, THEN multiply by speed.
Now try it yourself
Quiz · Question 1 of 16
What type of wave is sound?
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This topic in real past papers
Every real exam question we've found on sound waves, with a full worked answer.