Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A phon is a unit of perceived loudness level for pure tones. It is numerically equal to the sound pressure level in decibels (dB) of a 1 kHz tone that is perceived as equally loud.
5 Must Know Facts For Your Next Test
The phon scale is used to describe the subjective perception of loudness.
At 1 kHz, the number of phons directly equals the number of decibels.
Loudness levels in phons account for the frequency sensitivity of human hearing.
A phon measurement adjusts for the fact that different frequencies are perceived with different sensitivities at the same sound pressure level.
The concept was developed to create a standardized way to measure perceived loudness across various frequencies.
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Related terms
Decibel (dB): A logarithmic unit used to measure sound intensity. It quantifies sound levels relative to a reference level.