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Samar El-Sayed

Samar El-Sayed. Noise. Sound is Vibrational Energy. Travels in Waves from a Source. FREQUENCY INTENSITY. Cycles per Second Hertz (Hz). loudness of the sound Decibels (dB). How We Hear. Sound waves enter the ear canal striking the eardrum.

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Samar El-Sayed

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  1. Samar El-Sayed Noise

  2. Sound is Vibrational Energy Travels in Waves from a Source FREQUENCY INTENSITY Cycles per Second Hertz (Hz) loudness of the sound Decibels (dB)

  3. How We Hear • Sound waves enter the ear canal striking the eardrum. • When eardrum vibrates, ossicles conducts vibrations to the cochlea. • Tiny hairlike cells in cochlea respond to vibrations by generating nerve impulses. • Brain interprets nerve impulses as sound. Chem/Elec Acoustical Hydraulic Mechanical

  4. What is Noise? • Unwanted or undesired sound. • Sound that has potential to cause hearing impairment. • An intense sound capable of damaging the inner ear

  5. Effectsof Noise • Auditory • Acute acoustic trauma Sudden, permanent SNHL caused by single exposure to an intense Impulse sound, 130-140dB • Noise-induced hearing loss • Extra – auditory • Interfere with communication • Physiological effects • Annoyance

  6. Auditory effects of Noise Temporary threshold shift (TTS) • Temporary loss of hearing shortly after exposure to noise. • Resolves over a period of hours or days • Permanent threshold shift (PTS) • Permanent hearing loss due to damage of sensory cells.

  7. Hearing and Frequencies • Nerve cells in the cochlea are tuned to specific frequencies • Base of the cochlea is sensitive to high frequency sounds(red dots) • Tip of the cochlea is sensitive to low frequency sounds(green dots)

  8. Low noiseNormal cochlea At safe noise levels, sound waves move along the cochlea without damaging receptor cells • Safe Noise Levels

  9. High noiseDamaged cochlea High noise levels damage the first turn of the cochlea – where high frequency sounds are heard…and lost • Loud Noise Levels

  10. Is Permanent + 100% Preventable Noise-Induced Hearing Loss • Causes no pain • Causes no visible trauma • Leaves no visible scars • Is unnoticeable in its earliest stages • Takes years to notice a change

  11. Time-linked to noise exposure • High-frequency hearing loss • Usually bilateral (both ears) • Gradual progression over time • mostly irreversible • Appropriate symptoms (tinnitus, muffled hearing) • Indicators of NIHL

  12. Noise + Acoustics • Hearing Conservation Program • Action Level – 85 dB • Hearing Conservation Program implemented • Hearing protectors made available • Annual audiometric testing & training Permissible Exposure Limit – 90 dB • Hearing protectors required 90 95 85 dB TWA

  13. Elements of Hearing Conservation Program • Noise control measures • Engineering • Administrative • Hearing Protectors • Workers education • Noise Monitoring • Periodic audiometric evaluation

  14. ENGINEERING CONTROLS • Vibration Pads • Enclosures • Barriers • Isolation • ADMINISTRATIVE CONTROLS • Rotate Workers • Extended Breaks • 2nd/3rd Shift PERSONAL PROTECTIVE EQUIPMENT Hierarchy of Controls

  15. Time Weighted Average Permissible Exposure Limits

  16. Time Weighted Average 4 95 Permissible Exposure Limits

  17. Hearing Protection SelectionEarplugs • Advantages • Comfortable for extended use • Free head movements • Good for tight work spaces • Worn with hats, eye protection, respirators • Disadvantages • Must be replaced periodically • Small and can easily be lost • Hygiene issues in dirty environments

  18. Hearing Protection SelectionBands • Advantages • Very convenient for intermittent noise • Readily available around neck when not in use • Disadvantages • Lower attenuation than most earplugs • Some noise transmission through band

  19. Hearing Protection SelectionEarmuffs • Advantages • Easy to get proper fit • Good for intermittent noise • Advantages • Can feel hot/heavy with extended wear • Compatibility with other PPE

  20. The right hearing protector should feel comfortable • One protector may not satisfy all workers • Offer a variety of earplugs or earmuffs to meet varying worker needs and preferences • Proper care and maintenance can extend life and performance of HPDs • Examine and clean all multiple-use earplugs daily • Clean and replace ear cushions on earmuffs every 4-6 months • Select HPDs that can work with other PPE without compromise • Cap-mounted earmuffs for hard hats • Multiple-position earmuffs for full-brim hard hats • Ultraslim neckband earmuffs with welding shields Comfort Noise Reduction • Selecting HPDs with suitable attenuation for noise environment • Avoid overprotection in marginal noise environments • Consider banded earplugs for intermittent noise or electronic earmuffs for impact noise. • Every ear canal has its own shape and size • Ensure proper fit with variety of earplug sizes and shapes • Sized multiple-use earplugs • Low-pressure foam earplugs for smaller ear canals • Consider job requirements in HPD selection • Detectable earplugs for process industries • Hi-visibility earmuffs for dark/high traffic areas • Dielectric HPDs for electrical environments Size • Keep workers connected to their environment • Uniform attenuation allows speech/signals to be hear more naturally • Sound amplification earmuffs for workers with hearing impairment Communication Job Requirements Hygiene Use with Other PPE Hearing Protection Selection Factors

  21. 0 dB 0 dB 33 dB EAR #1 EAR #2 EAR #3 How much protection?

  22. Workers education • Effects of noise on hearing • Purpose of hearing protectors • Advantages and disadvantages of different types of hearing protectors • Attenuation of different types of hearing protectors • Instructions on selection, fitting, use, and care of hearing protectors • Purpose of audiometric testing

  23. Noise Measurement Devices PERSONAL DOSIMETER Sound “averaged” throughout day for sample employee/job SOUND LEVEL METER Sound is measured immediately in a specific area

  24. Pure tone audiometry • Basic test to find out if a hearing loss is present or not. • During the test the test person wears a headphone or insert ear phones through which pure tones at different frequencies are being presented. • level at which tones are barely audible is found, is the hearing threshold levels

  25. .

  26. Speech audiometry • A speech reception threshold (SRT) • Two-syllable words like "hotdog," baseball," and "cupcake" are presented at various intensity levels and the worker repeats them or point to a picture. • SRT is determined by the lowest level of sound intensity needed for the patient to correctly identify 50% of these words.

  27. Speech audiometry • Speech discrimination test • Evaluates the patient's ability to comprehend a list of single-syllable words presented at a comfortable listening level. • The percentage of words the worker is able to correctly repeat or identify is then recorded.

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