Loudness is the sensation most directly tied to sound intensity

Evidence

The sensat.ion that corresponds most closely to the sound intensity of the stimulus is loudness. The sensation-stimulus relation of loudness can be measured by answering the question how much louder (or softer) a sound is heard relative to a standard sound. This can be achieved by either searching for a ratio by changing the stimulus, or by judging a ratio of two sensations produced by two given stimuli. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1177

Categorization

• DEFINE: Establishes loudness as the intensity-correlated sensation and introduces ratio-scaling measurement.