7. sound

Compressions

Regions in a longitudinal wave where the particles of the medium are pushed closest together, creating areas of high density and pressure.

Rarefactions

Regions in a longitudinal wave where the particles of the medium are spread farthest apart, creating areas of low density and pressure.

Medium

The substance or material (solid, liquid, or gas) through which a mechanical wave travels.

Loudness

The human perception of a sound's energy or intensity, which increases with a larger wave amplitude.

Pitch

The human perception of how high or low a sound is, determined by the frequency of the sound wave.