Equal Loudness: Difference between revisions

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Here is an excerpt from [http://en.wikipedia.org/wiki/Equal-loudness_contour Wikipedia]

An '''equal-loudness contour''' is a measure of sound pressure ([http://en.wikipedia.org/wiki/Decibel dB] [http://en.wikipedia.org/wiki/~~Sound_pressure_levelSound pressure level~~ SPL]), over the [http://en.wikipedia.org/wiki/Frequency 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 [http://en.wikipedia.org/wiki/Phon phon], and is arrived at by reference to equal-loudness contours. By definition two sine waves, of differing frequencies, are said to have equal-loudness level measured in phons if they appear equally loud to the average young person without significant hearing impairment.

An '''equal-loudness contour''' is a measure of sound pressure ([http://en.wikipedia.org/wiki/Decibel dB] [http://en.wikipedia.org/wiki/Sound_pressure_level SPL]), over the [http://en.wikipedia.org/wiki/Frequency 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 [http://en.wikipedia.org/wiki/Phon phon], and is arrived at by reference to equal-loudness contours. By definition two sine waves, of differing frequencies, are said to have equal-loudness level measured in phons if they appear equally loud to the average young person without significant hearing impairment.

Equal-loudness contours are often referred to as 'Fletcher-Munson' curves, after the earliest experimenters, but this is now incorrect, the definitive curves being those defined in the international standard ISO 226:2003 which are based on a review of several modern determinations made in various countries.

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== Experimental determination==

The [[human]] auditory system is sensitive to frequencies from 20 ~~[[Hertz|~~Hz]] to a maximum of around 20,000 Hz, although the hearing range decreases with age. Within this range, the [[human ear]] is most sensitive between 1 and 5 [[kHz]], largely due to the resonance of the [[ear canal]] and the [[transfer function]] of the [[ossicles]] of the middle ear.

The human auditory system is sensitive to frequencies from 20 Hz to a maximum of around 20,000 Hz, although the hearing range decreases with age. Within this range, the human ear is most sensitive between 1 and 5 kHz, largely due to the resonance of the ear canal and the transfer function of the ossicles of the middle ear.

Equal-loudness contours were first measured by Fletcher and Munson using headphones (1933). In their study, listeners were presented with pure tones at various frequencies and over 10 dB increments in stimulus intensity. For each frequency and intensity, the listener was also presented with a reference tone at 1000 Hz. The reference tone was adjusted until it was perceived to be of the same loudness as the test tone. Loudness, being a psychological quantity, is difficult to measure, so [[Fletcher-~~Munson curves|~~Fletcher and Munson]] averaged their results over many test subjects to derive reasonable averages. The lowest equal-loudness contour represents the quietest audible tone and is also known as the [[absolute threshold of hearing]]. The highest contour is the [[threshold of pain]].

Equal-loudness contours were first measured by Fletcher and Munson using headphones (1933). In their study, listeners were presented with pure tones at various frequencies and over 10 dB increments in stimulus intensity. For each frequency and intensity, the listener was also presented with a reference tone at 1000 Hz. The reference tone was adjusted until it was perceived to be of the same loudness as the test tone. Loudness, being a psychological quantity, is difficult to measure, so [http://en.wikipedia.org/wiki/Fletcher-Munson_curves Fletcher and Munson] averaged their results over many test subjects to derive reasonable averages. The lowest equal-loudness contour represents the quietest audible tone and is also known as the [http://en.wikipedia.org/wiki/Absolute_threshold_of_hearing absolute threshold of hearing]. The highest contour is the [http://en.wikipedia.org/wiki/Threshold_of_pain threshold of pain].

A new experimental determination was made by [[Robinson-~~Dadson curves|~~Robinson and Dadson]] (1956) which was believed to be more accurate, and this became the basis for a standard (ISO 226) which was considered definitive until 2003, when the standard was revised on the basis of recent assessments by research groups worldwide.

A new experimental determination was made by [http://en.wikipedia.org/wiki/Robinson-Dadson_curves Robinson and Dadson] (1956) which was believed to be more accurate, and this became the basis for a standard (ISO 226) which was considered definitive until 2003, when the standard was revised on the basis of recent assessments by research groups worldwide.

== Recent revision aimed at more precise determination - ISO 226:2003 ==

@@ Line 6: / Line 6: @@
 Here is an excerpt from [http://en.wikipedia.org/wiki/Equal-loudness_contour Wikipedia]
-An '''equal-loudness contour''' is a measure of sound pressure ([http://en.wikipedia.org/wiki/Decibel dB] [http://en.wikipedia.org/wiki/Sound_pressure_levelSound pressure level SPL]), over the [http://en.wikipedia.org/wiki/Frequency 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 [http://en.wikipedia.org/wiki/Phon phon], and is arrived at by reference to equal-loudness contours. By definition two sine waves, of differing frequencies, are said to have equal-loudness level measured in phons if they appear equally loud to the average young person without significant hearing impairment.
+An '''equal-loudness contour''' is a measure of sound pressure ([http://en.wikipedia.org/wiki/Decibel dB] [http://en.wikipedia.org/wiki/Sound_pressure_level SPL]), over the [http://en.wikipedia.org/wiki/Frequency 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 [http://en.wikipedia.org/wiki/Phon phon], and is arrived at by reference to equal-loudness contours. By definition two sine waves, of differing frequencies, are said to have equal-loudness level measured in phons if they appear equally loud to the average young person without significant hearing impairment.
 Equal-loudness contours are often referred to as 'Fletcher-Munson' curves, after the earliest experimenters, but this is now incorrect, the definitive curves being those defined in the international standard ISO 226:2003 which are based on a review of several modern determinations made in various countries.
@@ Line 12: / Line 12: @@
 == Experimental determination==
-The [[human]] auditory system is sensitive to frequencies from 20 [[Hertz|Hz]] to a maximum of around 20,000 Hz, although the hearing range decreases with age. Within this range, the [[human ear]] is most sensitive between 1 and 5 [[kHz]], largely due to the resonance of the [[ear canal]] and the [[transfer function]] of the [[ossicles]] of the middle ear.
+The human auditory system is sensitive to frequencies from 20 Hz to a maximum of around 20,000 Hz, although the hearing range decreases with age. Within this range, the human ear is most sensitive between 1 and 5 kHz, largely due to the resonance of the ear canal and the transfer function of the ossicles of the middle ear.
-Equal-loudness contours were first measured by Fletcher and Munson using headphones (1933). In their study, listeners were presented with pure tones at various frequencies and over 10 dB increments in stimulus intensity.  For each frequency and intensity, the listener was also presented with a reference tone at 1000 Hz.  The reference tone was adjusted until it was perceived to be of the same loudness as the test tone. Loudness, being a psychological quantity, is difficult to measure, so [[Fletcher-Munson curves|Fletcher and Munson]] averaged their results over many test subjects to derive reasonable averages. The lowest equal-loudness contour represents the quietest audible tone and is also known as the [[absolute threshold of hearing]]. The highest contour is the [[threshold of pain]].
+Equal-loudness contours were first measured by Fletcher and Munson using headphones (1933). In their study, listeners were presented with pure tones at various frequencies and over 10 dB increments in stimulus intensity.  For each frequency and intensity, the listener was also presented with a reference tone at 1000 Hz.  The reference tone was adjusted until it was perceived to be of the same loudness as the test tone. Loudness, being a psychological quantity, is difficult to measure, so [http://en.wikipedia.org/wiki/Fletcher-Munson_curves Fletcher and Munson] averaged their results over many test subjects to derive reasonable averages. The lowest equal-loudness contour represents the quietest audible tone and is also known as the [http://en.wikipedia.org/wiki/Absolute_threshold_of_hearing absolute threshold of hearing]. The highest contour is the [http://en.wikipedia.org/wiki/Threshold_of_pain threshold of pain].
-A new experimental determination was made by [[Robinson-Dadson curves|Robinson and Dadson]] (1956) which was believed to be more accurate, and this became the basis for a standard (ISO 226) which was considered definitive until 2003, when the standard was revised on the basis of recent assessments by research groups worldwide.
+A new experimental determination was made by [http://en.wikipedia.org/wiki/Robinson-Dadson_curves  Robinson and Dadson] (1956) which was believed to be more accurate, and this became the basis for a standard (ISO 226) which was considered definitive until 2003, when the standard was revised on the basis of recent assessments by research groups worldwide.
 == Recent revision aimed at more precise determination - ISO 226:2003 ==