Phon

Equal-loudness contours

The phon is a logarithmic unit of loudness level for tones and complex sounds. Loudness is measured in sones, a linear unit. Human sensitivity to sound is variable across different frequencies; therefore, although two different tones may present an identical sound pressure to a human ear, they may be psychoacoustically perceived as differing in loudness. The purpose of the phon is to provide a logarithmic measurement (like decibels) for perceived sound magnitude, while the primary loudness standard methods result in a linear representation. A sound with a loudness of 1 sone is judged equally loud as a 1 kHz tone with a sound pressure level of 40 decibels above 20 micropascals.[1] The phon is psychophysically matched to a reference frequency of 1 kHz.[2] In other words, the phon matches the sound pressure level (SPL) in decibels of a similarly perceived 1 kHz pure tone.[3] For instance, if a sound is perceived to be equal in intensity to a 1 kHz tone with an SPL of 50 dB, then it has a loudness of 50 phons, regardless of its physical properties.[4] The phon was proposed in DIN 45631 and ISO 532 B by Stanley Smith Stevens.[5][failed verification]

  1. ^ William M. Hartmann, Signals, Sound, and Sensation, American Institute of Physics, 2004. ISBN 1-56396-283-7.
  2. ^ "dB: What is a decibel?". www.animations.physics.unsw.edu.au. Retrieved 2019-01-12.
  3. ^ Pease, C.B. (1974-07-01). "Combining the sone and phon scales". Applied Acoustics. 7 (3): 167–181. doi:10.1016/0003-682X(74)90011-5. ISSN 0003-682X.
  4. ^ "Loudness Units: Phons and Sones". hyperphysics.phy-astr.gsu.edu. Retrieved 2019-01-12.
  5. ^ UNSW Music Acoustics.