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Dr Mohammad Ghasemi.

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Presentation on theme: "Dr Mohammad Ghasemi."— Presentation transcript:

1 Dr Mohammad Ghasemi

2 Ear & WORK Maryam Saraei

3 Occupational Hearing loss
It is estimated that over 22 million workers are exposed to hazardous noise on the job and an additional nine million are at risk for hearing loss from other agents such as solvents and metals . Noise-induced hearing loss is 100 percent preventable but once acquired, hearing loss is permanent and irreversible.

4 Occupational Hearing loss
Occupational hearing loss may be partial or total unilateral or bilateral, and conductive, sensorineural, or mixed . In the workplace, hearing loss can be caused by blunt or penetrating head injuries, explosions and thermal injuries such as slag burns sustained when a piece of welder's slag penetrates the eardrum.

5 Ear anatomy

6 0-120 dB is rang of faintest noise to painful stimulation.
The normal human cochlea is capable of detecting and encoding sound waves across the frequency range extending from approximately 20 hertz (Hz) to 20,000 Hz. The most important range for human speech reception is between 500 Hz and 3000 Hz .

7 Normal PTA

8 Conductive Loss

9 Sensorineural Loss

10 Mixed Loss

11 Effects of Excessive Exposure
Primary Effects Effects on Communication and Performance Effects on Other Organs

12 Primary Effects Noise-induced temporary threshold shift
Noise-induced permanent threshold shift Acoustic trauma Tinnitus

13 Effects on Communication and Performance
Isolation Annoyance Difficulty concentrating Absenteeism Accidents

14 Other Effects Stress Muscle tension Ulcers Increased blood pressure

15 Sensorineural Hearing Loss
"Sensory" hearing loss is associated with irreversible damage to the inner ear. The term "neural" suggests a degeneration of the neural elements of the auditory nerve.

Result from a brief exposure to extremely loud noise (explosion) May also occur following single periods of exposure to continuous noise. (For example, several hours of unprotected exposure to a jet turbine producing sounds in the dB ) Acute NIHL can result in temporary or permanent damage

Risk of permanent hearing impairment is related to the duration and intensity of exposure as well as genetic susceptibility to noise trauma. prolonged exposure to sounds louder than 85 dBA is potentially injurious. most severe around 4000 Hz, with extension toward the "speech frequencies" ( Hz) occurring only after prolonged or severe exposure.

18 Risk Factors for NIHL: Unprotected Exposure to Noise(>85dB)
Hyperlipoproteinemia Diabetes Solvents Cigarette Smoking Eye Color Thyroid Abnormalities

19 Clinical Findings Bilateral, predominantly high-frequency sensori-neural hearing loss with a maximum drop of the pure tone thresholds occurring at or around 4000 Asymmetry can exist Frequently complain of gradual deterioration in hearing

20 Clinical Findings Difficulty in comprehending speech, especially in the presence of competing background noise vowel sounds are heard better than consonant sounds Frequently accompanied by tinnitus High frq. Tonal (ringing) Low frq. Tonal ( buzzing , blowing, hissing ) Non tonal (popping , clicking)

21 Clinical Findings Tinnitus frequency matches the frequency of the hearing loss seen on the audiogram and is about 5 dB above that threshold in loudness. SDS is normal in the early stages but may deteriorate as the loss becomes more severe

22 NIHL as specified by : 1. Always sensorineural.
2. Nearly always bilateral and symmetric. 3. Will not progress once noise exposure is stopped. 4. The frequency is the most severely effected and the higher frequencies (3-6kHz) are more affected than the lower frequencies (500Hz-2kHz). 6. Maximum losses typically occur after years of chronic exposure. 8. Continuous noise is more damaging than intermittent noise .

23 Audiogram Characteristics
Always sensorineural and high-frequency Usually bilateral and symmetric Typically the first sign is a notching of the audiogram at 3000,4000, or 6000 Hz, with recovery at 8000 hz Notch broaden over time with continuing exposure NIHL usually does not produce a loss >75 dB in high frequencies and >40 dB in lower frequencies

24 NIHL does not progress ( in excess of what would be expected from the addition of age related threshold shift) once the exposure to noise is discontinued The rate of hearing loss in NIHL is greatest during the first years of exposure. After 10 years of exposure further loss is negligible.

25 Other Characteristics
NIHL characteristically develops in the first years of exposure Rarely will an employee working in consistent noise have good hearing for 4-5 years and then develop progressive hearing loss from occupational cause unless condition has changed. The frequencies below 3 khz are almost never damaged by occupational noise without damage to the higher frequencies.

26 4 khz notch & abnormal SDS & good thresholds in speech frequencies indicates other etiologies
Exposure to noise less than 90 dBA ( TWA) cannot cause hearing loss with speech frequencies involvement even in susceptible employees.

27 Periodic audiogram of a site operator with noise exposure 91 dbA 6 hrs per day without hearing protection

28 Periodic audiograms of a repairman
Periodic audiograms of a repairman. Job change to compressor operator with 98 dbA noise exposure 4 hrs per day from hearing protection: yes

29 Unilateral or Asymmetric
Unequal or unilateral exposure to noise source Truck drivers, tractor drivers, Unequal fitting of hearing protective devices Anatomic difference between ear canals Preexisting unilateral or asymmetrical notch Maximal asymmetry in pure NIHL is 15 dB between left and right ear at 3 or 4 or 6 khz. In more asymmetry other causes or preexisting hearing loss must be ruled out

30 Unilateral NIHL ( crane operators with left-sided noise source)

31 Is this audiogram due to continuous noise exposure
Is this audiogram due to continuous noise exposure? ( A 38 yrs old “ring operator” exposed to continuous noise 92 dBA for 13 years )

32 And this audiogram? (another ring worker exposed to continuous noise 92 dBA for 13 years)



35 Compare with this audiogram
ادیوگرام مربوط به کاهش شنوایی ناشی از صوت زمانی که در فرکانسهای بالا به حداکثرافت می رسد ( 75 دسی بل ) حتما فرکانس های گفتاری نیز گرفتار هستند چون NIHL یک سیر تدریجی پیشرونده مشخص را طی می کند و در نتیجه ادیوگرام های قبلی نمی توانند بطور خالص ناشی از صوت باشند حتی اگر در یک کارگر مواجه با صوت غیر مجاز با مدت کافی مواجهه وجود داشته باشد.

36 Progressive course of NIHL



39 Periodic audiograms of 41-year-old employee ( site operator ) with unprotected noise exposure of 95 dbA 4 hrs per day from Hearing protector have been used from 1384.


41 Diagnosis of NIHL Greatest value in diagnosis: - History
- Noise exposure assessment (intensity & duration) - Serial audiograms

42 Differential Diagnosis of NIHL:
Presbycusis Hereditary Hearing Impairement Metabolic Disorders Sudden Sensorineural Hearing Loss Infections Central Nervous System Diseases Meniere’s Disease Nonorganic Hearing Loss

43 Key Points: Coductive hearing loss Mixed hearing loss
Inconsistent tests SRT 15dB>PTA Unilateral hearing loss History of exposure to gunfire/airplane engine noise Presbycusis

44 presbycusis hearing loss is a gradual, symmetric, progressive high frequency sensorineural associated with gradual deteriorating speech discrimination.



47 hereditary hearing impairment
Distinguished by a family history and early age at onset; however, there are delayed-onset forms of HHL . can be conductive, mixed, or sensorineural . Otosclerosis is an example of a progressive autosomal dominant hearing loss that can be conductive, mixed, or sensorineural hearing loss.

48 metabolic disorders DM, thyroid dysfunction, renal failure, autoimmune disease, hyperlipidemia, and hypercholesterolemia. May result in a sensorineural hearing loss that is bilateral, progressive, and high frequency.

49 sudden SNHL Sudden onset, usually with­in 1 or 2 hours, in the absence of precipitating factors. Almost always unilateral Sensorineural hearing loss (SNHL) Can be exhibited at low frequencies with improvement in the high frequencies, flat, or high frequency with good low-frequency hearing.

50 sudden SNHL Ranging from mild to severe
The etiology of SNHL is unknown; speculation as to viral, vascular insult, or inner ear membrane rupture .

51 Infections Meningitis and encephalitis Syphilis and Lyme
Congenital syphilis sufferer may develop symptoms in infancy or later in life that may also be associated with vestibular symptoms similar to Meniere syndrome; the hearing loss is usually bilateral.

52 Infections Late syphilis may present a slowly progressive sensorineural hearing loss and may also exhibit associated vestibular problems. Mumps may cause a severe, most typically unilateral sensorineural hearing loss

53 central nervous system disease
Cerebellopontine angle tumors, especially acoustic neuroma, may present progressive sensorineural hearing loss that is unilateral Demyelinating diseases (e.g., multiple sclerosis) may present a sudden unilateral hearing loss that typically recovers to some degree.

54 (endolymphatic hydrops)
meniere disease (endolymphatic hydrops) Fluctuating low frequency or flat unilateral sensorineural hearing loss Fullness or pressure in the affected ear Tinnitus Episodic disabling vertigo In early stage usually low frequency sensori-neural but over time it may progress to a flat severe hearing loss.

55 nonorganic hearing loss
Functional hearing loss for purposes of secondary gain is quite frequent. Poor correlation between the SRT and the average of the air conduction thresholds at 500, 1000, and 2000 Hz is the most common indication of functionality . Test-retest variability is also suggestive. In cases of suspected uni­lateral functional hearing loss, the Stenger test is useful .

56 prevention 85 dBA has been characterized as the approximate biologic threshold above which permanent shifts in hearing are possible. OSHA : the presence of occupational noise at or above an 8-hour TWA exposure of 85 dBA is the threshold that triggers the need to HCP .

57 Hearing conservation program (HCP)
A hearing conservation program (HCP) is the recognized method of preventing noise induced hearing loss in the occupational environment.

58 Hearing conservation program (HCP)
Noise monitoring Engineering controls Administrating controls Worker education Hearing Protection Devices (HPD) Periodic audiometric evaluation

59 noise monitoring The noise must be characterized :
1.Frequency (predominantly high, predominantly Low, or mixed) 2.Intensity (how loud it is) 3.Type (continuous> intermittent, or impulse) Anytime there is any change in production, process, equipment, or controls, all noise monitoring tests must be repeated .


61 Noise Measurement Sound level meter: Dosimeter:
measures ambient noise levels in decibels Dosimeter: sound level meter that integrates constant or fluctuating sound over time

62 Sound level meters

63 Noise dosimeter


65 Engineering controls Based on the information collected during noise monitoring. Possible engineering solutions: The source The path The receivers

66 Engineering controls The noise controls may involve the use of enclosures (to isolate sources or receivers), barriers (to reduce acoustic energy along the path), or distance In general, engineering controls are preferred but are not always feasible because of their costs and limits In technology.

67 Administrative controls
Reducing the amount of time a given worker might be exposed to a noise source in order to prevent the TWA noise exposure from reaching 85 dBA, and establishing purchasing guidelines to prevent introduction of equipment that would increase worker noise dose

68 Workers educations Workers must understand the potentially harmful effects of noise . In general, the use of HPDs by employee exposed to TWA noise levels of 85 dBA or greater is recommended.

69 Workers educations A good worker education program describes
Program objectives Existing noise hazards, Now hearing loss occurs, Purpose of audiometric testing, and What workers can do to protect themselves.


71 Hearing protection devices
Although the HCP is triggered by the presence of noise levels equal to or greater than an 8 hour TWA of 85 dBA, HPDs must attenuate worker exposure to an 8-hour TWA at or below 90 dBA

72 Hearing protection devices There are three basic types of HPDs :
Ear plugs or "aurals" (premolded, formable, and custom molded) Caps or "semiaurals" (with a band that compresses each end against the entrance of the ear canal) Ear muffs or "circumaurals"


74 Premolded ear plags (NRR)=23dB 5 color-coded sizes:
White (Extra Small) Green (Small) Orange (Medium) Blue (Large) Red (Extra Large) 74

75 Formable ear plags





80 Custom molded earplags


82 معايب مزايا Earplugs جايگذاري سخت تر حمل راحت
محدوديت در مشكلات گوش و آناتومي نياز به معاينه قبل از استفاده مزايا حمل راحت ارزان قابل استفاده با سايروسايل فردي حركت راحت سر و گردن

83 استفاده از ایرپلاگ های اسفنجی در مشاغلی که امکان آلودگی دستها وجود دارد مانند سوهان کاری، فرزکاری و در محیطهایی که تماس با مواد سوزاننده و محرک وجود دارد مناسب نمی باشد.

84 Noise Reduction Rating (NRR)=23dB
Ear muffs Noise Reduction Rating (NRR)=23dB 84

85 Ear muffs

86 Earmuff مزايا معايب حفاظت مناسب كنترل مناسب عدم نياز به معاينه گران
سنگين ناراحتي در گرما و رطوبت مشكلات استفاده توام با ساير وسايل كم كفايتي در موارد وجود موي بلند و ريش

87 مواجهه با گاز ازن تولید شده توسط بعضی از ژنراتورها و در جریان جوشکاری می توانند سبب سفت شدن فوم موجود درDOME ایرماف شوند .

88 Noise Reduction Rating
All HPD are assigned a standardized as NRR. NRRs are based on laboratory attenuation data and achieved under ideal conditions. Adjustment of the assigned NRR based on: A- Weighting scale adjustment B- Derating C- Combining HPDs

89 Example If a device has an NRR of 21 and workplace noise measurements were made using the "A" scale, then the predicted field attenuation or "relative performance" of the device would be (21 – 7) / 2 = 7 dBA. Such a device would be expected to provide protection where 8-hour TWA noise levels up to 97 (90 + 7) dBA are present .

90 Combining HPDs OSHA advises its inspectors that 5 dB are to be added after the weighting scale adjustment is applied to the device with the higher NRR .

91 Audiometric evaluation
Only quantitative means of assessing the overall effectiveness of a hearing conservation program. Results of audiometric testing must be shared with employees to ensure effectiveness.

92 Audiometry Baseline Audiogram Monitoring Audiograms Retest Audiograms
Confirmation Audiograms Exit Audiogram

93 Baseline Audiogram The baseline audiogram should be obtained within 30 days of enrollment in the HLPP It shall be preceded by a minimum of 12 hr of unprotected quiet. Use of hearing protectors should not be considered a substitute for an actual 12-hr quiet period.

94 Monitoring Audiograms
Monitoring audiometry shall be conducted no less than annually. Unlike baseline audiometry, these annual tests should be scheduled at the end of, or well into, the work shift. The results should be compared immediately with the baseline audiogram

95 Retest Audiograms Audiometry be repeated immediately after any monitoring audiogram that indicates a threshold shift of 15 dB or more at 500, 1000, 2000, 3000, 4000, or 6000 Hz in either ear. The worker should be reinstructed and the headphones refitted before conducting the retest.

96 Confirmation Audiograms
Audiometry should be conducted again within 30 days of any monitoring or retest audiogram that continues to show a significant threshold shift. A minimum of 12 hr of quiet shall precede the confirmation audiogram to determine whether the shift is a temporary or permanent change in hearing sensitivity

97 Exit Audiogram Audiometry should be conducted when a worker leaves employment or is permanently rotated out of an occupational noise exposure at or above 85 dBA as an 8-hr TWA. This exit audiogram, like the baseline, should be performed after a minimum of 12 hr of quiet.

98 8- hour time-weighted average (TWA)
Duration / Day hours Slow response dBA 24 80 16 82 8 85 4 88 2 91 1 94 0.5 97 1/4 100

99 calculation of impairment
(AAO-79 method)

100 Criteria for referral to otolaryngologist
Baseline audiogram: a- Average HL at 500, 1000, 2000, and 3000 Hz > 25 dB in either ear. b- Difference in average HL between the better and poorer ears > 15 dB at 500, 1000, and 2000Hz or > 30 dB at 3000, 4000, and 6000. Periodic audiogram: - Change for the worse in average HL in either ear compared to the baseline audiogram >15 dB at 500, 1000, and 2000Hz or >20 dB at 3000, 4000, and 6000 Hz. Other criteria: ear pain, drainage, dizziness, tinnitus, fluctuating or rapidly progressive hearing loss, and …

101 Indications for Removal from Noise

102 Thanks

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