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Quantification of hearing loss
Age of onset of deafness
Pre-lingual deafness
Post-lingual deafness
Hard-of-hearing
Unilateral hearing loss
Non-hearing auditory impairment
Types
As discussed above, there are three major types of hearing loss: neural/sensorineural, conductive, or a combination of both. Treatment depends upon the type of hearing loss that is present.
Quantification of hearing loss
An audiologist conducting an audiometric hearing test in a sound-proof testing booth
The severity of hearing loss is measured by the degree of loudness, as measured in decibels, a sound must attain before being detected by an individual. Hearing loss may be ranked as mild, moderate, severe or profound. It is quite common for someone to have more than one degree of hearing loss (i.e. mild sloping to severe). The following list shows the rankings and
their corresponding decibel ranges:
• Mild:
o for adults: between 25 and 40 dB
o for children: between 20 and 40 dB
• Moderate: between 41 and 55 dB
• Moderately severe: between 56 and 70 dB
• Severe: between 71 and 90 dB
• Profound: 90 dB or greater
The quietest sound one can hear at different frequencies is plotted on an audiogram to reflect one's ability to hear at different frequencies. The range of normal human hearing (from the softest audible sound to the loudest comfortable sound) is so great that the audiogram must be plotted using a logarithmic scale. This large normal range, and the different amounts of hearing loss at different frequencies, make it virtually impossible to accurately describe the amount of hearing loss in simple terms such as percentages or the rankings above.
Measuring hearing loss in terms of a percentage is debatable in terms of effectiveness, and has been compared to measuring weight in inches. Though in specific legal situations, where decibels of loss are converted via a recognized legal formula, one can infer a standardized "percentage of hearing loss" which is suitable for legal purposes only.
Another method for determining hearing loss, is the Hearing in Noise Test (HINT). HINT technology was developed by the House Ear Institute, and is intended to measure an ability to understand speech in quiet and noisy environments. Unlike pure-tone tests, where only one ear is tested at a time, HINT evaluates hearing using both ears simultaneously (binaural), as binaural hearing is essential for communication in noisy environments, and for sound localization.
Age of onset of deafness
The age at which the deafness develops is crucial to spoken language acquisition. Post-lingual deafness are far more common than pre-lingual deafness.
If the hearing loss occurs at a young age, interference with the acquisition of spoken language and social skills may occur. Hearing aids, which amplify the incoming sound, may alleviate some of the problems caused by hearing impairment, but are often insufficient. Cochlear implants artificially stimulate the VIIIth Nerve by providing an electric impulse substitution for the firing of hair cells. Cochlear implants are not only expensive, but require sophisticated programming in conjunction with patient training for effectiveness. People who have hearing impairments, especially those who develop a hearing problem in childhood or old age, require support and technical adaptations as part of the rehabilitation process.
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مقاله Quantification of hearing loss