Minimum audibility curve is a standardised graph of the threshold of hearing versus frequency for an average human, and is used as the reference level when measuring hearing loss with an
audiometerAn audiometer is a machine used for evaluating hearing loss. The invention of this machine is generally credited to Dr. Harvey Fletcher of Brigham Young University. Audiometers are standard equipment at ENT clinics and in audiology centers...
as shown on an
audiogramAn audiogram is a standard way of representing a person's hearing loss. Most audiograms cover the limited range 100Hz to 8000Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal' hearing, in dBHL...
.
Audiograms are produced using a piece of test equipment called an
audiometerAn audiometer is a machine used for evaluating hearing loss. The invention of this machine is generally credited to Dr. Harvey Fletcher of Brigham Young University. Audiometers are standard equipment at ENT clinics and in audiology centers...
, and this allows different frequencies to be presented to the subject, usually over calibrated headphones, at any specified level.
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Minimum audibility curve is a standardised graph of the threshold of hearing versus frequency for an average human, and is used as the reference level when measuring hearing loss with an
audiometerAn audiometer is a machine used for evaluating hearing loss. The invention of this machine is generally credited to Dr. Harvey Fletcher of Brigham Young University. Audiometers are standard equipment at ENT clinics and in audiology centers...
as shown on an
audiogramAn audiogram is a standard way of representing a person's hearing loss. Most audiograms cover the limited range 100Hz to 8000Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal' hearing, in dBHL...
.
Audiograms are produced using a piece of test equipment called an
audiometerAn audiometer is a machine used for evaluating hearing loss. The invention of this machine is generally credited to Dr. Harvey Fletcher of Brigham Young University. Audiometers are standard equipment at ENT clinics and in audiology centers...
, and this allows different frequencies to be presented to the subject, usually over calibrated headphones, at any specified level. The levels are, however, not absolute, but weighted with frequency relative to a standard graph known as the minimum audibility curve which is intended to represent 'normal' hearing. This is not the best threshold found for all subjects, under ideal test conditions, which is represented by around 0
PhonThe phon was proposed as a unit of perceived loudness level LN for pure tones by S. S. Stevens.-Definition:The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones...
or the threshold of hearing on 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, but is standardised in an ANSI standard to a level somewhat higher at 1kHz
http://books.google.co.uk/books?id=DPZ4hvf2gG0C&pg=PA74&lpg=PA74&dq=audiograms+referrence+levels&source=web&ots=b3Q22J-Yo0&sig=sQyzhk_ECTPocPLldvcnlItJzdk&hl=en#PPA56,M1. There are several definitions of the minimal audibility curve, defined in different international standards, and they differ significantly, giving rise to differences in audiograms according to the audiometer used. The ASA-1951 standard for example used a level of 16.5dB SPL at 1kHz whereas the later ANSI-1969/ISO-1963 standard uses 6.5dB SPL, and it is common to allow a 10dB correction for the older standard.
See also
- Audiogram
An audiogram is a standard way of representing a person's hearing loss. Most audiograms cover the limited range 100Hz to 8000Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal' hearing, in dBHL...
- Hearing range
For more detail on human hearing see Audiogram, Equal loudness contours and Hearing impairment.Hearing range usually describes the range of frequencies that can be heard by an animal or human, though it can also refer to the range of levels...
- Equal-loudness contour
An 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...
- Articulation index
The Articulation Index is a tool used by audiologists to predict the amount of speech that is audible to a patient with a specific hearing loss. The AI reading for a given patient can range from zero to 1.0, representing the proportion of the average speech signal that is audible...
- Pure tone audiometry
Pure tone audiometry is the key hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss. Thus, providing the basis for diagnosis and management. PTA is a subjective, behavioural measurement of hearing...
- Psychoacoustics
Psychoacoustics is the study of subjective human perception of sounds. Alternatively it can be described as the study of the psychological correlates of the physical parameters of acoustics.- Background :...
- Hearing (sense)
Hearing is one of the traditional five senses. It is the ability to perceive sound by detecting vibrations via an organ such as the ear...
- Audiology
Audiology is the branch of science that studies hearing, balance, and related disorders. Its practitioners, who treat those with hearing loss and proactively prevent related damage are audiologists. Employing various testing strategies Audiology (from Latin , "to hear"; and from Greek , -logia) is...
- Audiometry
Audiometry is the testing of hearing ability. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or distinguished speech from background noise. ...
- A-weighting
A Weighting curve is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A,...
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