Correct Option: B

Loudness is a subjective characteristic of a sound (as opposed to the sound-pressure level in decibels, which is objective and directly measurable). Perceived loudness of sound is a psycho-acoustic quantity that depends on sound pressure level, the frequency spectrum, and the time behavior of the sound in question. The sone is a unit of perceived loudness that was proposed by Stanley Smith Stevens in 1936.Being a unit of how loud a sound is perceived, the sone scale of loudness is based on data obtained from subjects who were asked to judge the loudness of pure tones and noise. One sone is arbitrarily set equal to the loudness of a 1,000-hertz tone at a sound level of 40 decibels (Encyclopedia Britannica).