website is devoted to
the evaluation of occupational hearing loss. The most common cause of
occupational hearing loss is
trauma from loud noise. The determination of hearing
impairment is often based upon the American Academy of Otolaryngology 1979
equation. There are many other different equations which can be used to calculate
hearing impairment. They vary between federal agencies, states, and
countries. Most USA courts now recognize the AAO 1979 formula, and its use
has been successfully argued in many legal settings (Byrum v. Newport News
Shipbuilding & Dry Dock Co., 14 B.R.B.S. 833 ).
PUB MED Searches:
When evaluating cases of occupational hearing loss, one must distinguish between Medical and Legal Causation. Medical Causation calls for scientific certainty, but Legal Causation only needs to be within a reasonable degree of medical certainty. In some settings, only a more likely than not or greater than 50% likelihood is needed.
Presbycusis is hearing loss associated with aging. In the medical-legal context, it is the "non-occupational" hearing loss, or "nosocusis" as described by Kryter in 1983, which the average individual of a certain age has. Compensation for presbycusis may be performed when evaluating occupational hearing losses. Go To Presbycusis Calculator
Often workers have a
preexisting hearing loss when they begin employment. Many years later,
upon retirement, the hearing loss is worse and the question is raised: Is
the worker's hearing loss at retirement due to added occupational noise exposure,
or is it just the combination of the worker's pre-employment hearing loss and
other environmental factors. The
Projection Calculator or
can give guidance to this question. This
calculator can also be used to project the worker's post-employment audiogram
into the future and determine the likely hearing impairment at any given
age. (The Master Calculator and Age Projection Calculators will determine the degree of
presbycusis in the initial audiogram. Subtract these values from the presbycusis
for the projected age; then add the difference to the thresholds in the initial audiogram, thus,
calculating the projected audiogram. All projected thresholds are also
off-set by the ISO-1999 compression factor and truncated at 100 dB.)
Age Projection of Audiogram
(Noise induced hearing loss and presbycusis are assumed to be additive.
--Macrae, JH. Audiology. 10:323-333,1971.
All thresholds are off-set by ISO-1999 Compression Factor for adding
presbycusis and noise induced hearing loss)
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