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An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels (dB) and the X axis represents frequency measured in hertz (Hz). [ 1 ]
The shape of the audiogram resulting from pure-tone audiometry gives an indication of the type of hearing loss as well as possible causes. Conductive hearing loss due to disorders of the middle ear shows as a flat increase in thresholds across the frequency range. Sensorineural hearing loss will have a contoured shape depending on the cause.
The result of the test is an audiogram diagram which plots a person's hearing sensitivity at the tested frequencies. On an audiogram an "x" plot represents the softest threshold heard at each specific frequency in the left ear, and an "o" plot represents the softest threshold heard at each specific frequency in the right ear.
Portable audiometer Maico, circa 1960s. An audiometer typically transmits recorded sounds such as pure tones or speech to the headphones of the test subject at varying frequencies and intensities, and records the subject's responses to produce an audiogram of threshold sensitivity, or speech understanding profile.
The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933. Until recently, it was common to see the term Fletcher–Munson used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
The result of most audiometry is an audiogram plotting some measured dimension of hearing, either graphically or tabularly. The most common type of audiogram is the result of a pure tone audiometry hearing test which plots frequency versus amplitude sensitivity thresholds for each ear along with bone conduction thresholds at 8 standard ...
The stimulus level is increased if the subject does not respond and decreased when a response occurs. Similar to the method of limits, the stimuli are adjusted in predetermined steps. After obtaining from six to eight reversals, the first one is discarded and the threshold is defined as the average of the midpoints of the remaining runs.
Minimum audibility curve is a standardized graph of the threshold of hearing frequency for an average human, and is used as the reference level when measuring hearing loss with an audiometer as shown on an audiogram.