The
phon was proposed as a unit of
perceivedIn philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was predicted that building perceiving machines would take about a decade,...
loudnessLoudness is the quality of a sound that is the primary psychological correlate of physical strength .Loudness, a subjective measure, is often confused with objective measures of sound pressure such as decibels or sound intensity. Filters such as A-weighting attempt to adjust sound measurements to...
level-Places:*Levél, a village in Hungary*Level, Ohio, a former community in the United States*Somerset Levels, a wetland area of central Somerset, England-Engineering-related:*A floor of a building or a mine...
LN for pure tones by
S. S. StevensS. S. Stevens may refer to:* Stanley Smith Stevens, an american psychologist* SS Stevens, a ship used as a floating dormitory...
.
The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones. By definition, 1 phon is equal to 1 dBSPL at a frequency of 1 kHz.
The
equal-loudness contourAn equal-loudness contour is a measure of sound pressure , over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon, and is arrived at by reference to equal-loudness contours...
s are a way of mapping the dBSPL of a pure tone to the perceived loudness level in phons.
The
phon was proposed as a unit of
perceivedIn philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was predicted that building perceiving machines would take about a decade,...
loudnessLoudness is the quality of a sound that is the primary psychological correlate of physical strength .Loudness, a subjective measure, is often confused with objective measures of sound pressure such as decibels or sound intensity. Filters such as A-weighting attempt to adjust sound measurements to...
level-Places:*Levél, a village in Hungary*Level, Ohio, a former community in the United States*Somerset Levels, a wetland area of central Somerset, England-Engineering-related:*A floor of a building or a mine...
LN for pure tones by
S. S. StevensS. S. Stevens may refer to:* Stanley Smith Stevens, an american psychologist* SS Stevens, a ship used as a floating dormitory...
.
Definition
The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones. By definition, 1 phon is equal to 1 dBSPL at a frequency of 1 kHz.
The
equal-loudness contourAn equal-loudness contour is a measure of sound pressure , over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon, and is arrived at by reference to equal-loudness contours...
s 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 curvesThe Fletcher–Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and W A Munson, and reported in a paper entitled "Loudness, its definition, measurement and calculation" in J.Acoust...
and
Robinson-Dadson curvesThe Robinson–Dadson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by D W Robinson and R S Dadson, and reported in a paper entitled "A re-determination of the equal-loudness relations for pure tones" in Br. J. Appl. Phys...
were in error.
The phon unit is not generally accepted according to the stringent criteria of
metrologyMetrology is the science of measurement. Metrology includes all theoretical and practical aspects of measurement.-Introduction:...
. It has not been accepted as a standard unit by the United States
National Institute of Standards and TechnologyThe National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce...
.
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
psychologicalPsychology is an academic and applied discipline involving the systematic, and sometimes scientific, study of human or animal mental functions and behavior...
and
physiologicalPhysiology is the science of the functioning of living systems. It is a subcategory of biology...
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.
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