Sound waves – frequency (pitch) and amplitude (loudness)

Integrated ScienceLight & SoundAges 12–13

A speaker membrane vibrates, causing air particles in a tube to bunch together and spread apart; these compression and rarefaction layers propagate as a sound wave while each particle merely oscillates about its rest position. Drag the frequency and amplitude sliders: a higher frequency vibrates the membrane faster, giving a higher pitch, while a larger amplitude makes particles vibrate more strongly, giving a louder sound. A displacement-vs-time graph shows the period T = 1/f; choose a medium (air, water, steel, vacuum) to see how the speed of sound differs and that sound cannot travel through a vacuum.