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ABNORMAL ABNORMAL NORMAL NORMAL 10 6 10 6 ABNORMAL ABNORMAL NORMAL NORMAL 10 6 10 6.

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ABNORMAL ABNORMAL NORMAL NORMAL 10 10 6 6
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Page 1: ABNORMAL ABNORMAL NORMAL NORMAL 10 6 10 6 ABNORMAL ABNORMAL NORMAL NORMAL 10 6 10 6.

ABNORMALABNORMAL

NORMALNORMAL101066

ABNORMALABNORMAL

NORMALNORMAL101066

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OCCUPATIONALOCCUPATIONAL HEARING LOSS HEARING LOSS

BY: MORTEZA DAVOODI BY: MORTEZA DAVOODI M.DM.D..

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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, Although NIHL is permanent, irreversible, and prevalent, it is irreversible, and prevalent, it is preventablepreventable..

In addition to the major problem of In addition to the major problem of NIHL, the ear is susceptible to NIHL, the ear is susceptible to other other environmental factorsenvironmental factors. .

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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.

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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

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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

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Differential diagnosis of Differential diagnosis of SNHLSNHL

(Nonoccupational Hearing Loss)(Nonoccupational Hearing Loss) PresbycusisPresbycusis

Gradual symmetrical progressive high frequency Gradual symmetrical progressive high frequency SNHLSNHL

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

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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

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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

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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.

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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 Hearing loss onset, progression, fluctuation and

symmetrysymmetry.. 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

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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.

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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

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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 communications only occurs with shouting, even if the workers stand next shouting, even if the workers stand next to each other.to each other.

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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 , depending upon the direction of blast.upon 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)

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Chronic NIHLChronic NIHL

Defining CharacteristicsDefining Characteristics

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Audiometric test roomsAudiometric test rooms

TABLE D-1 - MAXIMUM ALLOWABLE OCTAVE-BAND TABLE D-1 - MAXIMUM ALLOWABLE OCTAVE-BAND SOUND PRESSURE LEVELS FOR AUDIOMETRIC TEST SOUND PRESSURE LEVELS FOR AUDIOMETRIC TEST

ROOMS ROOMS ________________________________________________________________________________ Octave-band center Octave-band center frequency (Hz)............... 500 1000 2000 4000 frequency (Hz)............... 500 1000 2000 4000

8000 8000 Sound pressure level (dB) ... 40 40 47 57 Sound pressure level (dB) ... 40 40 47 57

62 62 ______________________________________________________________________________________________________________ ________________

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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.)

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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

Again

You Say

Something

?Speak Up

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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 limits

26 26 –– 40 40 Mild HL Mild HL

41 41 –– 55 55 Moderate HL Moderate HL

56 56 –– 70 70 Moderate to severe Moderate to severe HLHL

71 71 –– 90 90 Severe HL Severe HL

> 90> 90 Profound HL Profound HL

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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

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Noise ExposuresNoise Exposures

No exposure to No exposure to continuous, continuous, intermittent, or intermittent, or impact noise of a impact noise of a peak C-weighted level peak C-weighted level of 140 dB shall occur.of 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

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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

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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 who has completed the necessary education and training requirements.the 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.

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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 shows a shift from base line in excess of 10 db for the average hearing level at 2000, 3000, and for 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.

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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 adjust the audiogram, the employer shall follow the procedure described below. This follow the procedure described below. This procedure and the age correction tables were procedure and the age correction tables were developed by the developed by the National Institute for National Institute for Occupational Safety and HealthOccupational Safety and Health in a criteria in a criteria document. document.

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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 A. Finding the age at which the most recent

audiogram was taken and recording the audiogram was taken and recording the corresponding values of age corrections at 1000 Hz corresponding values of age corrections at 1000 Hz through 6000 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..

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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..

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Table FTable F––11——Age Correction Values in Decibels for MalesAge Correction Values in Decibels for Males

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Table F–1—Age Correction Values in Decibels for Males

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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..

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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 Difference in average hearing level between

the better and poorer ears of more than the better and poorer ears of more than 15db15db at 500, 1000, and 2000 Hz, or more than at 500, 1000, and 2000 Hz, or more than 3030 db db at 3000, 4000, and 6000 Hz.at 3000, 4000, and 6000 Hz.

Periodic audiogramsPeriodic audiograms Change for the worse in average hearing level Change for the worse in average hearing level

in either ear compared to the base line in either ear compared to the base line audiogram of more than 15db at 500, 1000, audiogram of more than 15db at 500, 1000, and 2000, or more than 20db at 3000, 4000, and 2000, or more than 20db at 3000, 4000, and 6000 Hz.and 6000 Hz.

Audiometric findings are inconsistentAudiometric findings are inconsistent

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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.

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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.””

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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..””

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HEARING PROTECTIVE HEARING PROTECTIVE DEVICES (HPDs)DEVICES (HPDs)

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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 Are usually quite comfortable to wear and they also can provide high noise attenuation they also can provide high noise attenuation values.values.

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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 may not be sealing properly. Take the earplug out and try again.try again. Illustrations and Photo courtesy of NIOSH

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HEARING PROTECTIVE DEVICES HEARING PROTECTIVE DEVICES (HPDs)(HPDs)

EarmuffsEarmuffs The cup material should be rigid and of large The cup material should be rigid and of large

volume so as to provide the best volume so as to provide the best low frequencylow frequency attenuation levels.attenuation 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 and less likely to cause external ear canal infections.cause external ear canal infections.

They are They are easier to remove and replaceeasier to remove and replace in conditions in conditions of intermittent noise exposure. of 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 In conditions of extremely high noise, it may be necessary to wear be necessary to wear both earplugs and both earplugs and earmuffsearmuffs together. together.

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Noise reduction ratingsNoise reduction ratings

NRRs are based on laboratory NRRs are based on laboratory attenuation data and achieved under attenuation data and achieved under ideal conditions.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.

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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 before being subtracted from the actual measured TWA noise levelsthe actual measured TWA noise levels

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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 determined adjustment) should be applied to determined its its ““relative performancerelative performance””..

OSHA does not require the 50% OSHA does not require the 50% derating.derating.

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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.

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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 .

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TinnitusTinnitus

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Diagnostic Approach to Diagnostic Approach to TinnitusTinnitus

Tinnitus is common, affecting up to Tinnitus is common, affecting up to 10 percent10 percent of the U.S. general population. of 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 The severity of tinnitus varies from an occasional awareness of a noise (e.g., ringing, occasional awareness of a noise (e.g., ringing, hissing, buzzing, roaring, clicking, or rough hissing, buzzing, roaring, clicking, or rough sounds) in one or both ears, to an unbearable sounds) in one or both ears, to an unbearable sound that drives some persons to contemplate sound that drives some persons to contemplate suicidesuicide. .

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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, and tinnitus associated with other tinnitus associated with other unilateral otologic symptomsunilateral otologic symptoms represent potentially more serious underlying disease than represent potentially more serious underlying disease than bilateral tinnitus. bilateral tinnitus.

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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.

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Tinnitus and Significant Medical HistoryTinnitus and Significant Medical History

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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.


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