Final answer:
The phon scale is an ordinal scale that compares the loudness of sounds across different frequencies, reflecting human perception rather than physical intensity.
Step-by-step explanation:
The phon scale is an ordinal level scale, which means it measures the intensity of the sound in a relative order, specifically pertaining to human perception of loudness. This scale is distinct from decibels, as decibels measure the physical intensity of sound. The phon scale utilizes equal-loudness curves, determined by subjective comparisons of different frequencies and intensities by a large number of people, to indicate how loud a sound is perceived to be. Sounds on the same curve are perceived as equally loud, despite potentially differing in frequency and intensity levels. It's important to note that at a frequency of 1000 Hz, phons are numerically equivalent to decibels. Therefore, the correct answer to the question is that the phon scale compares the loudness of sounds across different frequencies.