hearing conservation

30%

• at 25 db
• risk at 80 dba= 3%
• at 85 dba=15%
• at 90dba=29%

• how the hearing loss is calculated
• the level of noise exposure
• number of years of exposure

• function of age other than nihl
• importance of differentiating general risk from excessive risk

as a % with material hearing impairment in a noise pop after subtracting the % who would normally incur such impairment from other causes in non exposed pop

• in 1997 based on its occupational noise and hearing survey conducted from 1968 to 1971
• recalc was necessary because of the porlific use of  hearing protection begun in early 1980s which would confound a determination of dose response relationships for contemporary workers

• 1. considers non linear efects of noise
• 2. uses the definition of hearing handicap as proposed by asha which is the average hearing loss at 1, 2, 3 and 4 with a 25 db low fence

• hearing loss
• effects on a person's well being

• annoyance
• sleep disturbances
• speech effects

• higher heart rate
•  change in resp pattern
• chages in blood chem
• causes stress
• muscle response

• affects human performance
• reduces ability to focus
• fine motor skills
• concentration
• annoyance, irritalility
• reduces muscular precision

• smoking
• certain cancer drugs
• airborne toxins 
• hl is variable

• use of articulation index which shows what you should be hearing
•     percentage of speech components that are audible
• speech interference level (SIL) METHOD
•     acceptability of background noise

• using octave band sound level meter
• vocal effort
• avg sound pressure level over 500, 1000, 2000 and 4000

• at a distance beyond 6-9 feet
• 6 = normal com
• 9 = forced com

• 55 for day 
• 45 for night

• a single high intensity noise event such as an explosion
• impulsive, high intensity noise causes mechanical damage
• outer hair cells distorted immediately
• middle ear changes may occur with perforated tm or ossicles dislocated

• nihl
• repeated exposure to moderately high intensity noise
• insidious nature of nihl
• physiochemical damage
• tinnitus and muffled hearing after exposure are warning signs
• 4 notch on audiogram

• temporary threshold shift will recover in 12-16 hours post exposure
• need to have that time 12-16 filled with effective quiet below 75 dba

• at 3, 4, and 6
• frist sharp cochlear turn around is at 4 tonotopic
• turbulance and overstimulation of basilar membrane
• may also see:
•     problems in acoustic transfer function of outer ear
•     high freq incr in sound pressure at the eardrum
•     ear canal resonance around 2500-3
•     half octave to a full octave above this is about 35-30 hz

• firearm because its a hgh freq noise,
• most impulsive noises mean a notch at 6
• head shadow causes asymmetry of loss (ie if you use firearm, ear opposite the shot may have more of a loss than the shooting ear.

military

contained refs to excessive noise but did not prescribe limits or acknowledge occupational hearing loss prob

• occupational safety and health act of 1970
• created within the department of labor
• charged with establishing safety and health standards for all of general industry
• created niosh nat inst for occupational safety and health

• develops criteria for safe occupational exposures to workplace hazards and recommends standards
• communicates recommended standards to osha and others

• 85 dba for 8 hours
• risk of developing hihl is 8%
• 3 db exchange rate

• 90 
• mine safety and health admin uses 90 too
• 25% excess risk
•  5 db exchange rate

• in 1981
• they can change enforcement policies but they can not change the law

• no
• only transportation, oil drilling and servicing, agriculture, construction, and mining

• only continuous type noises, not impulsive noises
• impulsive noises at 140 dba are not to be exceeded for any amount of time

• exposure assessment
• engineering and admin controls
• proper use of hearing protectors
• audiometric eval
• ed and motivation
• recordkeeping
• program audits and eval

• key individual
• communication
•     voice concerns
•     communication line open
• management support
•     must be apparent
•     must be consistent
•     policy of reinforcement

• baseline following quiet period of 14 hours for osha, 12 hours for niosh (<75 dba)
• within 6 months of employment for osha
• 30 days for niosh

• if in working environment above 85dba need to be tested annually
• at the end of shift
• if hearing change, retest within 30 days
• restest at beginning of shift

• notify employee in writing within 21 days
• reinstruct emp on use of hearing protection
• refit with alternative protection if necessary
• monitor emps use of hearing protection
• document

• change of 10 db or more
• must be present on 2 tests

• controversy
• osha requires
• decision must be made by professional supervisor not tech
• revised if change is consistent over two annual tests

• vans
• manual audiometer
• self recording audiometer
• industrial sound booth-looks like a large refrig

• ambient noise levels
• upward spread of masking
• low freq noise is more prevalent at industrial sites than in professional or commercial buildings

• must be tested prior to audiometric testing
• can only test down to 25 db for 500 hz

• council for accreditation inn occupational hearing conservation
• influenced government agencies
• multi disciplinary and non profit
• requried certification or its equivalent

• 1. physical problem related to hearing protection
• 2. suspect test is not valid

5, 1, 2, 3, 4, 6 tabular audiogram used higher incidence of malingering in an industrial pop

• loss>25 dbhl at 5, 1, 2, and 3 difference btw ears
• >15db avg at 5, 1, 2Hz
• >30 db avg at 3, 4, 6
• employer need not pay costs

• when there is a worsening compared to the baseline audiogram of 
• >15db avg at 5, 1, 2
• >20 db avg at 3, ,4, 6
• employer need not pay

• standard thres shift
• pta osha gets worse by 10db or more compared to baseline

osha freqs are at 2, 3, 4 and then PTA is the avg of the 3/3

• history of ear pain, drainage, felling of fullness or discomfort, sudden or rapid hearing loss, severe persistent tinnitus
• evidence of excessive cerumen
• employer need not pay

• improvement
• revise baseline if pta osha improves 5 db or more over two consecutive annual tests

• if pta osha worsens by 10db or more on two consecutive annual tests it must be revised
• baselines are made for each ear

• low=material impairment
• high=complete impairment

difference btw the low and high fences, expressed as %

binaural hearing is better than monaural hearing, no consensus

for disadvantage, loss of wages, or loss of employability that the hearing loss creates

a deviation or change for the worse in either aud structure or function, usually outside the range of normal

disadvantage imposed by a hearing impairment on a person's communicative performance in activities of daily living

the determination of a financial award for the loss of function caused by any hearing impairment that results in significant hearing handicap

40-50 hours/week of on had to be considered a sizeable exposure compared to only 1-4 hours/week of non oc noise

85dba

• it does not affect noise regulations
• created noise reduction rating (nrr) ear plugs