What is the objective term for the subjective term "loudness"?

The objective term correlating with the subjective perception of "loudness" is intensity. Intensity refers to the measurable aspect of sound, specifically the amount of energy carried by a sound wave per unit area. It is expressed in watts per square meter and provides a numerical representation of how loud a sound is, in contrast to loudness, which can vary based on individual perception and experience.

By contrast, pitch relates to the frequency of the sound waves and how high or low a sound is perceived. Volume is often used colloquially to mean loudness but is not a precise scientific term. Sound pressure, while related to sound intensity and also an objective measurement, more specifically refers to the local pressure variation from atmospheric pressure produced by a sound wave rather than a direct measure of loudness. Intensity serves as the most appropriate term to represent the quantifiable aspect corresponding to the subjective experience of loudness.