Which term describes the subjective magnitude of sound, influenced primarily by intensity?

The term that best describes the subjective magnitude of sound, primarily influenced by its intensity, is loudness. Loudness is a perceptual characteristic of sound that relates to how we perceive the strength or volume of the sound waves reaching our ears. It is largely determined by the intensity, or amplitude, of the sound waves; higher intensity translates to a greater perception of loudness.

While pitch refers to the perceived frequency of a sound, and frequency measures how many cycles of sound waves occur in a second, these are distinct from loudness. Amplitude also refers to the physical measurement of sound wave intensity but does not encapsulate the subjective experience of sound as loudness does. Thus, loudness is specifically tied to our perception of sound's intensity, making it the correct answer in this context.