ABNORMALABNORMAL
NORMALNORMAL101066
OCCUPATIONALOCCUPATIONAL HEARING LOSS HEARING LOSS
BY: MORTEZA DAVOODI BY: MORTEZA DAVOODI M.DM.D..
INTRODUCTIONINTRODUCTION Despite widespread institution of hearing Despite widespread institution of hearing
conservation programs in noisy conservation programs in noisy industries, NIHL is currently one of the industries, NIHL is currently one of the most commonmost common occupational diseases. occupational diseases.
Although NIHL is permanent, irreversible, Although NIHL is permanent, irreversible, and prevalent, it is and prevalent, it is preventablepreventable..
In addition to the major problem of NIHL, In addition to the major problem of NIHL, the ear is susceptible to the ear is susceptible to other other environmental factorsenvironmental factors. .
Safe noise exposureSafe noise exposure It is It is impossibleimpossible to establish to any to establish to any clear-cut clear-cut
distinction distinction between between ““safesafe”” and and ““unsafeunsafe”” noise noise exposure.exposure.
Because of the Because of the normal variation in normal variation in susceptibility susceptibility between individuals, it is not between individuals, it is not possible scientifically to set a realistic possible scientifically to set a realistic standard for exposure to noise that will standard for exposure to noise that will protect everyone who is exposed.protect everyone who is exposed.
Generally, limits are set with the intention of Generally, limits are set with the intention of protecting protecting 90%90% or more of an exposed or more of an exposed population.population.
How hearing maybe How hearing maybe impairedimpaired
Infection of the ear Infection of the ear Infection of external earInfection of external ear Chronic infection of the middle earChronic infection of the middle ear
Obstruction or injury by physical agentsObstruction or injury by physical agents Impacted cerumenImpacted cerumen Foreign bodiesForeign bodies Trauma to the ear (Slag burns)Trauma to the ear (Slag burns) A sudden, intense pressure waveA sudden, intense pressure wave Prolonged noise exposure Prolonged noise exposure Barotrauma (aerotitis)Barotrauma (aerotitis)
Middle ear damage due to rapid changes in altitudeMiddle ear damage due to rapid changes in altitude
Radiation induced damageRadiation induced damage Radiation to head and neckRadiation to head and neck
How hearing maybe How hearing maybe impairedimpaired
Toxic agentsToxic agents Quinine and its derivativesQuinine and its derivatives Organic solvents, heavy metals, CO, NSAIDS, Organic solvents, heavy metals, CO, NSAIDS,
cisplatin, furosemide, Tobacco (nicotine) and cisplatin, furosemide, Tobacco (nicotine) and aspirine (salicylates) are possible causes in aspirine (salicylates) are possible causes in hypersusceptible patients.hypersusceptible patients.
Antibiotics : Antibiotics : streptomycin, neomycin, kanamycin, paromomycin, streptomycin, neomycin, kanamycin, paromomycin,
rifampin, aminoglycosides , vancomycin, rifampin, aminoglycosides , vancomycin, symmetrical progressive high frequency SNHLsymmetrical progressive high frequency SNHL
Diseases :Diseases : Meningitis, tumors, mumps, measles, scarlet Meningitis, tumors, mumps, measles, scarlet
fever, diphtheria, respiratory infectionsfever, diphtheria, respiratory infections
Differential diagnosis of Differential diagnosis of SNHLSNHL
(Nonoccupational Hearing Loss)(Nonoccupational Hearing Loss) PresbycusisPresbycusis
Gradual symmetrical progressive high frequency SNHLGradual symmetrical progressive high frequency SNHL
Hereditary hearing impairment (HHI):Hereditary hearing impairment (HHI): Is distinguished by a Is distinguished by a family history family history and and early age early age at at
onset. e.g; otosclerosis (Can be conductive, mixed, or onset. e.g; otosclerosis (Can be conductive, mixed, or SNHL)SNHL)
Metabolic disordersMetabolic disorders DM, Thyroid dysfunction, renal failure, autoimmune DM, Thyroid dysfunction, renal failure, autoimmune
disease, hyper-lipidemia and hyper-cholesterolemiadisease, hyper-lipidemia and hyper-cholesterolemia SNHL that is SNHL that is bi-lateralbi-lateral, , progressiveprogressive, and , and high high
frequencyfrequency
Differential diagnosis of Differential diagnosis of SNHLSNHL
(Nonoccupational Hearing Loss)(Nonoccupational Hearing Loss) Sudden SNHLSudden SNHL
Sudden onset usually within Sudden onset usually within 1 or 2 hours 1 or 2 hours in the absence in the absence of precipitating factorsof precipitating factors
Almost always unilateralAlmost always unilateral Can be exhibited at Can be exhibited at low frequencies, flat or high low frequencies, flat or high
frequenciesfrequencies hearing loss. hearing loss. The degree of HL can be from mild to severe .The degree of HL can be from mild to severe .
Infectious origin:Infectious origin: Bacteria or virus infections including Bacteria or virus infections including meningitis meningitis and and
encephalitis.encephalitis. HL can be unilateral, but is usually HL can be unilateral, but is usually bilateral.bilateral. MumpsMumps may cause a rather severe, most typically may cause a rather severe, most typically
unilateral SNHLunilateral SNHL
Differential diagnosis of Differential diagnosis of SNHLSNHL
(Nonoccupational Hearing Loss)(Nonoccupational Hearing Loss)
CNS disease:CNS disease: Cerebellopontine angle Cerebellopontine angle tumors tumors
especially acoustic neuroma maybe especially acoustic neuroma maybe present present progressive SNHL that is progressive SNHL that is unilateralunilateral. .
MS MS : : sudden unilateral sudden unilateral hearing loss hearing loss that typically recovers to some degree.that typically recovers to some degree.
Menieres diseaseMenieres disease Fluctuating Fluctuating low frequency or flatlow frequency or flat
unilateral SNHLunilateral SNHL, , fullness fullness or pressure or pressure in the affected ear, in the affected ear, tinnitustinnitus and and episodic disabling episodic disabling vertigovertigo
Exteraauditory effects of Exteraauditory effects of noisenoise
Alterations in blood pressure Alterations in blood pressure Due to release of adrenocortical hormones and Due to release of adrenocortical hormones and
sympathomimetic mediatorssympathomimetic mediators Adverse influences on existing illnesses Adverse influences on existing illnesses
Hyperlipoproteinemia and diabetes Hyperlipoproteinemia and diabetes Pregnancy and noise:Pregnancy and noise:
It is unclear what effect exposure to noise It is unclear what effect exposure to noise during pregnancy may have on the unborn during pregnancy may have on the unborn child, in terms of increased rate of child, in terms of increased rate of miscarriage, low birth-weight, or prematurity.miscarriage, low birth-weight, or prematurity.
CLINICAL EVALUATION OF CLINICAL EVALUATION OF HEARING LOSSHEARING LOSS
Detailed work and health historyDetailed work and health history AgeAge Family historyFamily history Ototoxic chemicals and drugsOtotoxic chemicals and drugs Presence of tinnitusPresence of tinnitus Noise exposure (occupational and non occup.)Noise exposure (occupational and non occup.) Hearing loss onset, progression, fluctuation and symmetryHearing loss onset, progression, fluctuation and symmetry.. the use of hearing protection devicesthe use of hearing protection devices Radiation to the head and neckRadiation to the head and neck Head injury Head injury CNS infections CNS infections
Complete otologic examination,Complete otologic examination, Audiologic examinationAudiologic examination
Importance of the historyImportance of the history
A careful evaluation of the workers A careful evaluation of the workers medical, occupational, and family medical, occupational, and family history history is probably the is probably the most important most important stepstep in the diagnostic procedure. in the diagnostic procedure.
The following factors regarding The following factors regarding past and present occupationspast and present occupations
should be evaluatedshould be evaluated Job titlesJob titles Type of work performed Type of work performed Duration of each type of activityDuration of each type of activity Dates of employment for each job activityDates of employment for each job activity Condition of Condition of PPEPPE used and frequency and used and frequency and
duration of periods of useduration of periods of use Nature of noiseNature of noise exposure include exposure include
frequency, intensity and average durationfrequency, intensity and average duration
Estimation of noise Estimation of noise exposureexposure
It is estimated that workers in an It is estimated that workers in an 85 dB85 dB environment will have to speak loudly,environment will have to speak loudly,
While those in While those in 85-90 dB85-90 dB will have to shout will have to shout
to communicate at arm length.to communicate at arm length.
As the surrounding noise reaches As the surrounding noise reaches 95 db95 db , , communications only occurs with shouting, communications only occurs with shouting, even if the workers stand next to each even if the workers stand next to each other.other.
NOISE INDUCED HEARING NOISE INDUCED HEARING LOSSLOSS
Acoustic traumaAcoustic trauma SNHLSNHL CHLCHL MixedMixed TinnitusTinnitus Can more severe than NIHL, especially in the Can more severe than NIHL, especially in the low and low and
middle frequencies.middle frequencies. DisequilibriumDisequilibrium In addition to immediate hearing loss, affected In addition to immediate hearing loss, affected
individuals may also complain of individuals may also complain of vertigo, tinnitus and vertigo, tinnitus and painpain. .
The injury may be The injury may be unilateral or bilateralunilateral or bilateral, depending upon , depending upon the direction of blast.the direction of blast.
SNHL from acoustic trauma may exhibit SNHL from acoustic trauma may exhibit some recoverysome recovery from initial levels; patient need to be followed for from initial levels; patient need to be followed for 4 to 6 4 to 6 monthmonth..
Temporary threshold shiftTemporary threshold shift (TTS)(TTS) Permanent threshold shift (PTS)Permanent threshold shift (PTS)
Chronic NIHLChronic NIHL Defining CharacteristicsDefining Characteristics
Audiometric test roomsAudiometric test rooms
TABLE D-1 - MAXIMUM ALLOWABLE OCTAVE-BAND SOUND TABLE D-1 - MAXIMUM ALLOWABLE OCTAVE-BAND SOUND PRESSURE LEVELS FOR AUDIOMETRIC TEST ROOMS PRESSURE LEVELS FOR AUDIOMETRIC TEST ROOMS ________________________________________________________________________________
Octave-band center Octave-band center frequency (Hz)............... 500 1000 2000 4000 frequency (Hz)............... 500 1000 2000 4000
80008000 Sound pressure level (dB) ... 40 40 47 57 Sound pressure level (dB) ... 40 40 47 57
62 62 _______________________________________________________________________________________________________________ _______________
Factors Affecting NIHLFactors Affecting NIHL Noise Intensity or Sound PressureNoise Intensity or Sound Pressure Frequency or PitchFrequency or Pitch Length of Daily ExposureLength of Daily Exposure Duration of Exposure in YearsDuration of Exposure in Years Individual SusceptibilityIndividual Susceptibility Other Factors (disease, genetics, Other Factors (disease, genetics,
lifestyle, age, etc.)lifestyle, age, etc.)
NOISE INDUCED HEARING NOISE INDUCED HEARING LOSSLOSS
Clinical presentation of Clinical presentation of NIHL:NIHL: Irreversible and usually Irreversible and usually
bilaterally symmetricbilaterally symmetric SNHL, SNHL, High frequencyHigh frequency hearing loss in hearing loss in
the region around 4000 Hz, with the region around 4000 Hz, with recovery at higher frequencies.recovery at higher frequencies.
Often accompanied by high Often accompanied by high frequency ringing frequency ringing tinnitustinnitus. .
Persons with NIHL typically Persons with NIHL typically complain of being able to hear complain of being able to hear but but not understand speechnot understand speech..
Beg PardonExcuse Me
Say WhatHuh?
Come
AgainYou Say
Something
?Speak Up
Scale of Hearing Scale of Hearing ImpairmentImpairment
Threshold (dB HL)Threshold (dB HL) Degrees of Degrees of ImpairmentImpairment-10 -10 –– 25 25 Within normal limits Within normal limits26 26 –– 40 40 Mild HL Mild HL41 41 –– 55 55 Moderate HL Moderate HL56 56 –– 70 70 Moderate to severe HL Moderate to severe HL71 71 –– 90 90 Severe HL Severe HL> 90> 90 Profound HL Profound HL
There are a number of indicators There are a number of indicators that will suggest the need for that will suggest the need for
careful consideration of causes careful consideration of causes other than noiseother than noise CHLCHL
MIXED hearing lossMIXED hearing loss Indicates that exposure to noise is not the only causeIndicates that exposure to noise is not the only cause
Inconsistent responses during different testsInconsistent responses during different tests Indicates the possibility of malingering or functional Indicates the possibility of malingering or functional
lossloss If SRT is 15dB or more than the average of the If SRT is 15dB or more than the average of the
pure tone levels at 500, 1000, and 2000 Hz, a pure tone levels at 500, 1000, and 2000 Hz, a psychogenic loss or malingering should be psychogenic loss or malingering should be suspected.suspected.
A pronounced loss in one earA pronounced loss in one ear
Noise ExposuresNoise Exposures
No exposure to No exposure to continuous, continuous, intermittent, or intermittent, or impact noise of a peak impact noise of a peak C-weighted level of C-weighted level of 140 dB shall occur.140 dB shall occur.
No exposure shall No exposure shall exceed a time exceed a time weighted average of weighted average of 115 dBA for 115 dBA for continuous noise.continuous noise.
SourceSourcedBAdBAWhisperWhisper2020
RefrigeratorRefrigerator4040
ConversationConversation6060
Average TVAverage TV7474
BlenderBlender8080
SourceSourcedBAdBAWalkmanWalkman9090
WoodworkingWoodworking93-12093-120
Gun ShotGun Shot130-140130-140
Riding Riding MotorcycleMotorcycle
9090
Snow MobileSnow Mobile120120
Rock ConcertRock Concert140140
Asymmetric hearing lossAsymmetric hearing loss Greater noise exposure in one earGreater noise exposure in one ear
Most indoor factory environment, are highly Most indoor factory environment, are highly reverberant so that one ear rarely receives reverberant so that one ear rarely receives significantly more noise than the other.significantly more noise than the other.
Non occupational noise sources Non occupational noise sources (Hunters).(Hunters).
Menieres diseaseMenieres disease Sudden idiopathic SNHLSudden idiopathic SNHL Acoustic neuromasAcoustic neuromas
Audiometric surveillance Audiometric surveillance for NIHLfor NIHL
The The OSHAOSHA hearing conservation program mandates hearing conservation program mandates audiometric surveillance of workers who are audiometric surveillance of workers who are exposed to noise levels equal to or exceeding exposed to noise levels equal to or exceeding 85 db85 db on an 8h TWA. (when beginning work and then on an 8h TWA. (when beginning work and then annually).annually).
This routine audiometric testing can be performed This routine audiometric testing can be performed by an by an audiometric technicianaudiometric technician who has completed the who has completed the necessary education and training requirements.necessary education and training requirements.
For the base line audiogram, the individual should For the base line audiogram, the individual should not have been exposed to loud noise for at least not have been exposed to loud noise for at least 16h 16h priorprior to testing, to avoid to testing, to avoid TTS. TTS.
Subsequent surveillance tests Subsequent surveillance tests do not requiredo not require noise noise free interval.free interval.
OSHA regulations require testing at the frequencies OSHA regulations require testing at the frequencies of 500, 1000, 2000, of 500, 1000, 2000, 30003000, 4000, , 4000, 60006000 and 8000 Hz. and 8000 Hz.
Audiometric surveillance Audiometric surveillance for NIHLfor NIHL
The results of the periodic audiogram should be The results of the periodic audiogram should be compared to thecompared to the base linebase line. If the employees test . If the employees test shows a shift from base line in excess of 10 db for shows a shift from base line in excess of 10 db for the average hearing level at 2000, 3000, and the average hearing level at 2000, 3000, and 4000 Hz in either ear (4000 Hz in either ear (STSSTS) a ) a retest retest may be may be performed within performed within 30 days30 days. If the shift persists, . If the shift persists, the employee must be informed in writing within the employee must be informed in writing within 21 days21 days, , fittedfitted with hearing protectors if not with hearing protectors if not already using them, already using them, refittedrefitted and counseled if and counseled if already using protectors, and already using protectors, and referredreferred for a for a clinical clinical audiologic evaluationaudiologic evaluation and/or otologic and/or otologic evaluation if appropriate. evaluation if appropriate.
Calculations and Application of Calculations and Application of Age Corrections to AudiogramsAge Corrections to Audiograms
(This appendix is non-mandatory )(This appendix is non-mandatory )
In determining whether a standard threshold In determining whether a standard threshold shift (STS) has occurred, allowance may be shift (STS) has occurred, allowance may be made for the contribution of aging to the made for the contribution of aging to the change in hearing level by adjusting the most change in hearing level by adjusting the most recent audiogram. recent audiogram. If the employer choosesIf the employer chooses to to adjust the audiogram, the employer shall follow adjust the audiogram, the employer shall follow the procedure described below. This procedure the procedure described below. This procedure and the age correction tables were developed and the age correction tables were developed by the by the National Institute for Occupational National Institute for Occupational Safety and HealthSafety and Health in a criteria document. in a criteria document.
Calculations and Application of Calculations and Application of Age Corrections to AudiogramsAge Corrections to Audiograms
(This appendix is non-mandatory )(This appendix is non-mandatory )
I. Determine from Tables FI. Determine from Tables F––1 or F1 or F––2 the age correction 2 the age correction values for the employee by:values for the employee by: A. Finding the age at which the most recent audiogram A. Finding the age at which the most recent audiogram
was taken and recording the corresponding values of was taken and recording the corresponding values of age corrections at 1000 Hz through 6000 Hz;age corrections at 1000 Hz through 6000 Hz;
B. Finding the age at which the baseline audiogram B. Finding the age at which the baseline audiogram was taken and recording the corresponding values of was taken and recording the corresponding values of age corrections at 1000 Hz through 6000 Hz.age corrections at 1000 Hz through 6000 Hz.
II. Subtract the values found in step (I)(B) from the value II. Subtract the values found in step (I)(B) from the value found in step (I)(A).found in step (I)(A).
III. The differences calculated in step (II) represented III. The differences calculated in step (II) represented that portion of the change in hearing that may be due to that portion of the change in hearing that may be due to agingaging..
Example: Example: Employee is a 32-year-old male. The Employee is a 32-year-old male. The audiometric history for his right ear is shown in decibels audiometric history for his right ear is shown in decibels
belowbelow..
Table FTable F––11——Age Correction Values in Decibels for MalesAge Correction Values in Decibels for Males
Table F–1—Age Correction Values in Decibels for Males
Go to Table FGo to Table F––1 and find the1 and find the age correction values (in dB) age correction values (in dB) for 4000 Hz at age 27 and age 32for 4000 Hz at age 27 and age 32..
CRITERIA FOR REFERAL OF CRITERIA FOR REFERAL OF INDIVIDUALS TO AN INDIVIDUALS TO AN OTOLARYNGOLOGISTOTOLARYNGOLOGIST
Baseline audiogramBaseline audiogram Average hearing levels at 500, 1000, 2000, and Average hearing levels at 500, 1000, 2000, and
3000 Hz greater than 3000 Hz greater than 2525 db in either ear. db in either ear. Difference in average hearing level between the Difference in average hearing level between the
better and poorer ears of more than better and poorer ears of more than 15db15db at at 500, 1000, and 2000 Hz, or more than 500, 1000, and 2000 Hz, or more than 3030 db at db at 3000, 4000, and 6000 Hz.3000, 4000, and 6000 Hz.
Periodic audiogramsPeriodic audiograms Change for the worse in average hearing level in Change for the worse in average hearing level in
either ear compared to the base line audiogram either ear compared to the base line audiogram of more than 15db at 500, 1000, and 2000, or of more than 15db at 500, 1000, and 2000, or more than 20db at 3000, 4000, and 6000 Hz.more than 20db at 3000, 4000, and 6000 Hz.
Audiometric findings are inconsistentAudiometric findings are inconsistent
CRITERIA FOR REFERAL OF CRITERIA FOR REFERAL OF INDIVIDUALS TO AN INDIVIDUALS TO AN OTOLARYNGOLOGISTOTOLARYNGOLOGIST
Ear painEar pain DrainageDrainage DizzinessDizziness Severe persistent tinnitusSevere persistent tinnitus Fluctuating or rapidly progressive Fluctuating or rapidly progressive
hearing losshearing loss Presence of accumulated cerumen or Presence of accumulated cerumen or
other foreign materials within the ear other foreign materials within the ear canal.canal.
PREVENTIONPREVENTION A hearing conservation program has consisted A hearing conservation program has consisted
of at least seven identifiable elements:of at least seven identifiable elements: Monitoring hearing hazardsMonitoring hearing hazards Engineering and administrative controlsEngineering and administrative controls Audiometric evaluationAudiometric evaluation Personal hearing protective devicesPersonal hearing protective devices Education and motivationEducation and motivation Record keepingRecord keeping Program evaluation Program evaluation
““By By showingshowing the worker his personal record of the worker his personal record of hearing sensitivity, the nurse or physician has hearing sensitivity, the nurse or physician has a a most effective devicemost effective device for the promotion of for the promotion of hearing protection.hearing protection.””
HEARING PROTECTIVE DEVICES HEARING PROTECTIVE DEVICES (HPDs)(HPDs)
What is the best hearing protector? What is the best hearing protector? The answer is:The answer is: ““the best protector is the one the best protector is the one
properly fittedproperly fitted and the one you and the one you wearwear..””
HEARING PROTECTIVE HEARING PROTECTIVE DEVICES (HPDs)DEVICES (HPDs)
HEARING PROTECTIVE DEVICES HEARING PROTECTIVE DEVICES (HPDs)(HPDs)
EarplugsEarplugs Custom moldedCustom molded
Provide satisfactory attenuation if properly Provide satisfactory attenuation if properly fitted.fitted.
Require cleaning and maintenance Require cleaning and maintenance Offer few advantages over the less expensive Offer few advantages over the less expensive
foam plugs.foam plugs. Expandable foam plugExpandable foam plug
Are usually quite comfortable to wear and they Are usually quite comfortable to wear and they also can provide high noise attenuation values.also can provide high noise attenuation values.
Proper Use of Hearing Proper Use of Hearing ProtectionProtection
Earplugs must be properly insertedEarplugs must be properly insertedsource: source: http://www.cdc.gov/niosh/mining/topics/hearingloss/earplug.htmhttp://www.cdc.gov/niosh/mining/topics/hearingloss/earplug.htm
1. Roll1. Roll the earplug up into a small, thin "snake" with the earplug up into a small, thin "snake" with your fingers. You can use one or both hands.your fingers. You can use one or both hands.
2. Pull2. Pull the top of your ear up and back with your the top of your ear up and back with your opposite hand to straighten out your ear canal. The opposite hand to straighten out your ear canal. The rolled-up earplug should slide right in.rolled-up earplug should slide right in.
3. Hold3. Hold the earplug in with your finger. Count to 20 or the earplug in with your finger. Count to 20 or 30 out loud while waiting for the plug to expand and fill 30 out loud while waiting for the plug to expand and fill the ear canal. Your voice will sound muffled when the the ear canal. Your voice will sound muffled when the plug has made a good seal.plug has made a good seal.
Check the fitCheck the fit when you're all done. Most of the foam when you're all done. Most of the foam body of the earplug should be within the ear canal. Try body of the earplug should be within the ear canal. Try cupping your handscupping your hands tightly over your ears. If sounds are tightly over your ears. If sounds are much more muffled with your hands in place, the earplug much more muffled with your hands in place, the earplug may not be sealing properly. Take the earplug out and try may not be sealing properly. Take the earplug out and try again.again.
Illustrations and Photo courtesy of NIOSH
HEARING PROTECTIVE DEVICES HEARING PROTECTIVE DEVICES (HPDs)(HPDs)
EarmuffsEarmuffs The cup material should be rigid and of large volume The cup material should be rigid and of large volume
so as to provide the best so as to provide the best low frequencylow frequency attenuation attenuation levels.levels.
Since earmuffs do not require insertion into the ear Since earmuffs do not require insertion into the ear canal, they are canal, they are more hygienicmore hygienic and less likely to cause and less likely to cause external ear canal infections.external ear canal infections.
They are They are easier to remove and replaceeasier to remove and replace in conditions of in conditions of intermittent noise exposure. intermittent noise exposure.
The The singular disadvantagesingular disadvantage to these devices is that to these devices is that they are they are cumbersome and bulky.cumbersome and bulky.
In conditions of extremely high noise, it may be In conditions of extremely high noise, it may be necessary to wear necessary to wear both earplugs and earmuffsboth earplugs and earmuffs together.together.
Noise reduction ratingsNoise reduction ratings
NRRs are based on laboratory attenuation NRRs are based on laboratory attenuation data and achieved under ideal conditions.data and achieved under ideal conditions.
Actual noise reduction achieved under Actual noise reduction achieved under field conditions using any HPDs will be field conditions using any HPDs will be much lower than the assigned NRR.much lower than the assigned NRR.
Noise reduction ratingsNoise reduction ratings Weighting Scale Adjustment:Weighting Scale Adjustment:
If workplace noise levels are determined using If workplace noise levels are determined using the the ““CC”” scale (dBC) on the monitoring scale (dBC) on the monitoring instrumentation, the assigned NRR may be instrumentation, the assigned NRR may be subtracted directly from the actual measured subtracted directly from the actual measured TWA noise levelsTWA noise levels
If workplace noise levels are determined using If workplace noise levels are determined using the the ““AA”” scale (dBA) on the monitoring scale (dBA) on the monitoring instrumentation, the assigned NRR must be instrumentation, the assigned NRR must be reduced by reduced by 7db 7db before being subtracted from the before being subtracted from the actual measured TWA noise levelsactual measured TWA noise levels
Noise reduction ratingsNoise reduction ratings
50% Derating:50% Derating: In order to more accurately predict the NRR In order to more accurately predict the NRR
of HPDs during actual use, a 50% derating of HPDs during actual use, a 50% derating of the assigned NRR (after weighting scale of the assigned NRR (after weighting scale adjustment) should be applied to adjustment) should be applied to determined its determined its ““relative performancerelative performance””..
OSHA does not require the 50% OSHA does not require the 50% derating.derating.
Derate by TypeDerate by Type
Derate the hearing protector Derate the hearing protector attenuation by type using the following attenuation by type using the following requirements:requirements: A. Subtract 7 dB from the published Noise A. Subtract 7 dB from the published Noise
Reduction Rating (NRR).Reduction Rating (NRR). B. Reduce the resulting amount by:B. Reduce the resulting amount by:
1. 20% for earmuffs,1. 20% for earmuffs, 2. 40% for form-able earplugs, or2. 40% for form-able earplugs, or 3. 60% for all other earplugs.3. 60% for all other earplugs.
Noise reduction ratingsNoise reduction ratings
Combining HPDs:Combining HPDs: Under such circumstances, OSHA Under such circumstances, OSHA
advises its inspectors that 5 dB are to advises its inspectors that 5 dB are to be added after the weighting scale be added after the weighting scale adjustment is applied to the device with adjustment is applied to the device with the higher NRR .the higher NRR .
TinnitusTinnitus
Diagnostic Approach to Diagnostic Approach to TinnitusTinnitus
Tinnitus is common, affecting up to Tinnitus is common, affecting up to 10 percent10 percent of of the U.S. general population. the U.S. general population.
It is most prevalent between It is most prevalent between 40 and 70 years40 and 70 years of of age, has a roughly equal prevalence in men and age, has a roughly equal prevalence in men and women, and occasionally can occur in children.women, and occasionally can occur in children.
The severity of tinnitus varies from an occasional The severity of tinnitus varies from an occasional awareness of a noise (e.g., ringing, hissing, awareness of a noise (e.g., ringing, hissing, buzzing, roaring, clicking, or rough sounds) in buzzing, roaring, clicking, or rough sounds) in one or both ears, to an unbearable sound that one or both ears, to an unbearable sound that drives some persons to contemplate suicidedrives some persons to contemplate suicide. .
Diagnostic Approach to TinnitusDiagnostic Approach to Tinnitus
Epidemiologic data reveal that approximately Epidemiologic data reveal that approximately one fourthone fourth of of persons with tinnitus are discomforted by it, whereas the persons with tinnitus are discomforted by it, whereas the remaining three fourths experience the condition without remaining three fourths experience the condition without significant symptoms. significant symptoms.
Subjective tinnitus, which is more common, is heard only by Subjective tinnitus, which is more common, is heard only by the patient. Objective tinnitus can be heard through a the patient. Objective tinnitus can be heard through a stethoscope placed over head and neck structures near the stethoscope placed over head and neck structures near the patient's ear.patient's ear.
In general, In general, pulsatilepulsatile tinnitus, tinnitus, unilateralunilateral tinnitus, and tinnitus tinnitus, and tinnitus associated with other associated with other unilateral otologic symptomsunilateral otologic symptoms represent represent potentially more serious underlying disease than bilateral potentially more serious underlying disease than bilateral tinnitus. tinnitus.
Causes of TinnitusCauses of Tinnitus SUBJECTIVE TINNITUS SUBJECTIVE TINNITUS
Otologic disorders are the most common cause of Otologic disorders are the most common cause of subjective tinnitus. Most cases of tinnitus result subjective tinnitus. Most cases of tinnitus result from the from the same conditions that cause hearing losssame conditions that cause hearing loss..
Both CHL & SNHLBoth CHL & SNHL
OBJECTIVE TINNITUS OBJECTIVE TINNITUS Objective tinnitus is rare. Patients with objective Objective tinnitus is rare. Patients with objective
tinnitus typically have a tinnitus typically have a vascularvascular abnormality, abnormality, neurologicneurologic disease, or disease, or eustachianeustachian tube dysfunction. tube dysfunction.
Patients experience worsening of symptoms at Patients experience worsening of symptoms at nightnight and usually do not have other otologic complaints. and usually do not have other otologic complaints.
Tinnitus and Significant Medical HistoryTinnitus and Significant Medical History
Where to Get More Where to Get More InformationInformation
http://www.cdc.gov/niosh/topics/noise/default.html. . National Institute for Occupational National Institute for Occupational Safety.Safety.
http://www.osha.gov/..Occupational Occupational Safety and Health Administration.Safety and Health Administration.
http://www.bgsu.edu/offices/envhs/ppe/documents/ppeprogram.pdf. Bowling Green State University. . Bowling Green State University. Personal Protective Equipment.Personal Protective Equipment.