Sound is a longitudinal wave — air molecules vibrate back and forth in the same direction as the wave travels. This creates alternating regions:
- Compressions: regions where air molecules are pushed together (higher pressure)
- Rarefactions: regions where air molecules are spread apart (lower pressure)
Crucially, the air molecules themselves do NOT travel with the sound — they vibrate back and forth around a fixed average position. Only the pattern of pressure differences (the wave) moves forward. This is why your ears detect sound even when you're far from the source — the pattern of compressions travels all the way to you.
This deep dive covers Sound as a Longitudinal Wave within Sound Waves for GCSE Physics. Revise Sound Waves in Waves for GCSE Physics with 16 exam-style questions and 15 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 2 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Sound Waves
What type of wave is sound?
Describe how a sound wave is produced and how energy is transferred by a longitudinal wave.