loudness
n. the subjective magnitude of sound. It is determined primarily by intensity but is also affected by other physical properties, such as frequency, spectral configuration, and duration. The unit proposed for loudness is the sone: One sone is defined as the subjective magnitude of a 1 kHz tone presented at 40 dB SPL (decibels sound-pressure level), based on loudness judgments by listeners. Loudness approximately doubles for each 10 dB increase in intensity. The loudness level is the level in decibels SPL of a 1 kHz tone that is judged to be equally as loud as the test sound. The unit is the phon: A sound whose loudness level is 40 phons has a loudness equal to that of a 1 kHz tone presented at 40 dB SPL.