The loudness of a sound, or volume of a sound wave, can be determined by the amplitude of the sound wave. Both pitch and volume can affect how "loud" a sound is and how it affects human ears specifically.
Pitch refers to the frequency of the sound wave. High frequencies result in a higher-pitched sound, like a whistle. Lower frequencies result in a lower-pitched sound, like the low sound emitted from a bass or cello. When looking at a sound wave graph, the higher-pitched sounds feature waves that are closer together, or more tightly wound, while lower-pitched sounds feature waves that are farther apart.
Volume or loudness is determined by the amplitude of the sound wave. The amplitude of the sound wave depends on the vibration caused by the source of the sound. The larger the vibration caused, the louder the sound will be. The smaller the vibration caused, the softer, or lower in volume, the sound will be. This can be evident with a guitar string that is plucked. If the guitar string is heavily plucked (pulled farther from its original tight position), the resulting sound is louder, due to the increased vibration of particles in the air caused by the significant movement of the string. If the guitar string is lightly plucked, the resulting sound is softer, due to the lower level of particle vibration in the air. When looking at a sound wave graph, the louder sounds feature waves that have higher amplitude, while softer sounds feature waves that have lower amplitude.