Final answer:
Loudness is determined by a sound wave's amplitude and the ear's sensitivity to frequency, while pitch is the perception of the frequency. Timbre is influenced by the unique frequencies and intensities from different instruments.
Step-by-step explanation:
The characteristics of a sound wave that determine the loudness and pitch that we perceive are its amplitude and frequency, respectively. Loudness, which has units called phons, is largely dependent on the sound wave's amplitude and the ear's sensitivity to different frequencies. Pitch, on the other hand, is the perception of frequency, with higher frequencies being perceived as higher pitches and lower frequencies as lower pitches. The timbre or tone quality of a sound is influenced by the instrument's distinct frequencies and intensities.