phon

unit of measurement
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Share
Share to social media
URL
https://www.britannica.com/science/phon
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

Related Topics:
acoustics
loudness
unit

phon, unit of loudness level. The loudness level of a sound is a subjective, rather than an objective, measure. To measure loudness, the volume of a 1,000-hertz reference tone is adjusted until it is perceived by listeners to be equally as loud as the sound being measured. The loudness level, in phons, of the measured sound is then equal to the sound-pressure level, in decibels, of the adjusted reference sound above the standard reference level, which is the minimum audible threshold. A variation of one phon in the loudness level of a sound is approximately the smallest change in sound-pressure level detectable by the human ear under normal listening conditions.