Question

which best describes loudness?
the subjective measurement of the intensity of sound
the subjective measurement of the wavelength of a sound wave
an inherent measurement of the intensity of sound
an inherent measurement of the wavelength of a sound wave

Explanation:

Loudness is a subjective perception. It relates to the intensity of sound (how much energy the sound wave carries). Wavelength is related to pitch (not loudness). "Inherent" is incorrect as loudness depends on perception. So, loudness is the subjective measurement of the intensity of sound.

Answer:

the subjective measurement of the intensity of sound