Hearing: How we notice sound waves and how the information from sound waves is carried to the brain.
Hearing involves detecting sound waves - waves of vibrations in the air.
These vibrations bounce around until they reach our ears. That's sound.

Frequency: the number of cycles per second from peak to peak:
High frequency: high pitch
Low frequency: low pitch

Amplitude: Strength of the sound wave: peak to valley height.
Big amplitude: loud.
Small amplitude: soft.

Pure tones, like a tuning fork, come from one sound wave.
Timbre (TAM-ber) the mixture of sound waves contained by one sound we hear.
A flute and a piano might make a sound with the same pitch and amplitude, but they sound different because they have different timbre.