Phon
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The phon was proposed in DIN 45631 and ISO 532 B as a unit of perceived loudness level LN for pure tones by S. S. Stevens.[1]
Definition
The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones.[2] By definition, 1 phon is equal to 1 dBSPL at a frequency of 1 kHz.[3]
The equal-loudness contours are a way of mapping the dBSPL of a pure tone to the perceived loudness level in phons. These are now defined in the international standard ISO 226:2003, and the research on which this document is based concluded that earlier Fletcher–Munson curves and Robinson-Dadson curves were in error.[citation needed]
The phon unit is not an SI unit in metrology. It has not been accepted as a standard unit by the United States National Institute of Standards and Technology.[citation needed]
The phon model can be extended with a time-varying transient model which accounts for "turn-on" (initial transient) and long-term, listener fatigue effects. This time-varying behavior is the result of psychological and physiological audio processing. The equal-loudness contours on which the phon is based apply only to the perception of pure steady tones: tests using octave or third-octave bands of noise reveal a different set of curves, owing to the way in which the critical bands of our hearing integrate power over varying bandwidths and our brain sums the various critical bands.[clarification needed][citation needed]
See also
References
- ^ UNSW Music Acoustics
- ^ William M. Hartmann, Signals, Sound, and Sensation, American Institute of Physics, 2004. ISBN 1563962837.
- ^ Nave, C. R. (2002-02-10). Loudness Units: Phons and Sones. HyperPhysics. Retrieved on 2008-07-10 from http://hyperphysics.phy-astr.gsu.edu/hbase/sound/phon.html.