phon

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The phon is a unit of loudness level for pure tones. Its purpose is to compensate for the effect of frequency on the perceived loudness of tones.^[1] The phon was proposed in DIN 45631 and ISO 532 B by S. S. Stevens.^[2]

Definition

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 (L_N) 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

• Sone
• A-weighting
• Decibel

References

External links

• Explanation with definitions
• Conversion: loudness level L (phons) to Loudness N and vice versa