Volume depends mainly on amplitude, so larger vibrations are heard as louder sound.

The longer version

Amplitude describes how far particles swing from their resting position during each cycle, and that swing sets the pressure difference arriving at the ear. Bigger swings carry more energy, excite a wider patch of the inner ear, and fire nerve fibres more often, which the brain reads as louder.

Perceived loudness is not simply proportional to that swing: the ear weights some frequencies more heavily, so a low rumble and a mid-range hiss of equal pressure are not judged equal. Doubling amplitude lifts level by only a modest step on the decibel scale, and roughly ten times the energy is needed before a listener calls something twice as loud.

Where this entry sits

Sound and Music gathers facts about how vibrations move through air and water, how ears turn them into meaning, and how instruments and notation shape what listeners hear. Expect echoes, pitch, volume, acoustics, and the odd silence in between. The full list sits on the Sound and Music page, where every entry is listed in order.