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14 Cards in this Set
- Front
- Back
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presbycusis
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age related hearing loss
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Professions concerned about noise
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Acoustical engineering
Industrial engineering Architecture Industrial hygiene Audiology Safety engineering Industrial medicine E.N.T. |
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Noise Induced Hearing Loss (NIHL)
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Sudden (explosion, gunshot, firecracker) = acoustic trauma
Long term loss = NIHL (cochlear damage Drop in hearing at 3K—6K Hz (noise notch) Recruitment |
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Temporary Threshhold Shift (TTS)
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Monday—Friday worker in noise
If noise is continued we get Noise induced permanent threshold shift (NIPTS) |
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Threshhold Levels
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threshold of hearing = 0—25dBHL
threshold of discomfort (TD) = 120 dBSPL threshold of pain = 140 dBSPL NIHL = 85 dB |
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Medical Aspects
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1908 Workman compensation—occupational injuries
1948 (Walsh-Healey Act) New York City awarded a man for NIHL who had not lost work or income 6 month wait till claim so TTS is eliminated last employer is liable Occupation Safety & Health Administration (OSHA) and OSHA Act established, 1971 |
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Percentage of Hearing Loss
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average 500, 1000, 2000 and 3000 Hz
subtract 25 from average = monaural loss multiply X 1.5% up to 100% Binaural loss is better ear is weighted 5 X the poorer ear Some states include provisions for normal aging loss |
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Noise measurements
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Sound level meter
A scale = resembles the human ear B scale = between A and C C scale = flat response Noise analyzers Octave Band Analyzer—measures sound in band widths (31.5, 63, 125, 250, 500, 1K, 2K, 4K, 8K and 16K Hz High quality tape recorder (for analysis in lab) Computers - analysis of wave forms Dosimeter - a sound level meter worn by the worker which is capable of accumulating and integrating noise exposure during a work day |
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Noise survey (with dosimeter)
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Calibrate instrumentation
Select locations where surveys are to be done (i.e. near employees) Get accurate readings with sound level meter Plot locations Re-calibrate |
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Intensity Level (IL) versus Sound Pressure Level (SPL)
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Double sound power = 3 dB increase
Double sound pressure = 6 dB |
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Damage Risk Criteria
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Walsh Healey Act set worker exposure limits
National Institute for Occupational Safety and Health (NIOSH) OSHA, 1971 (Dept. of Labor)—established 85 dBA standar |
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Noise Control - Engineering Design
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Decrease energy at source of vibration
Change coupling between vibration and sound radiating system Change structure that radiates sound so less sound radiated |
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Alterations in the Pathways of Sound
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Change relation between operator and noisy machinery (i.e. move worker to a quieter job after so much noise exposure)
Add acoustic barriers between source and listener Enclose machinery to contain noise Enclose operator so he is isolated from the noise |
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Hearing protection
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plugs
custom earplugs muffs |
