General Knowledge - Physics - Discussion

Intensity (Objective) : It is a purely physical quantity that depends on the energy transmitted per unit area per unit time (Watt/m^{2}). It is measured using instruments (like a sound level meter) and does not depend on the listener's ear or brain. Thus, it has an objective existence.

Loudness (Subjective) : In contrast, "Loudness" is how our ears perceive sound. Two sounds of the same intensity may sound differently loud to different people depending on their hearing sensitivity. Therefore, loudness has a subjective existence.