The phon scale has several important properties:
: The modern standard for these curves is defined by ISO 226, which provides the current data for how humans perceive loudness across the audible spectrum. Phon vs. Sone: Understanding the Difference phon scale
Definition: By definition, the number of phons for a given sound is numerically equal to the sound pressure level (in dB SPL) of a 1 kHz pure tone judged equally loud by a normal-hearing listener. The phon scale has several important properties: :
The is the unit of loudness level. By definition, a sound has a loudness of $N$ phons if it is perceived by the average listener to be as loud as a 1,000 Hz tone at $N$ decibels SPL. phon scale
