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Noise and Vibration

Noise and Vibration. Chapter 21. Noise - History. 100 Years – Noise Exposure results in permanent hearing Loss! 1918 – Vibration causes permanent damage to hands and fingers. Sound Wave. Physics of Sound. C = Speed of propagation λ = c/f C = speed f = frequency λ = wavelength.

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Noise and Vibration

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  1. Noise and Vibration Chapter 21 Industrial Hygiene

  2. Noise - History • 100 Years – Noise Exposure results in permanent hearing Loss! • 1918 – Vibration causes permanent damage to hands and fingers. Industrial Hygiene

  3. Sound Wave Industrial Hygiene

  4. Physics of Sound • C = Speed of propagation • λ = c/f • C = speed • f = frequency • λ = wavelength Industrial Hygiene

  5. Physics • Frequency = 1000 cycles per second • C = 1128.6 feet/sec (344 meters/sec) • Λ = 1128.6/125 hz • =9.02 feet Industrial Hygiene

  6. Physics • Sound is pressure • 1 P = 1 Newton/m2 • P = Pascal • L = 10Log(P/Pref)2 • Pref = 20 µPa Industrial Hygiene

  7. Physics • Sound Pressure = 0.2 Pascals What is • Sound level? • L = 10Log(0.2/20 µPa)2 • L = 80 dB • dB = decibels (deci = 1/10) Industrial Hygiene

  8. Directional Industrial Hygiene

  9. Sound • dBA vrs dBC weighting • A = close to human hearing • C = Flat Industrial Hygiene

  10. Industrial Hygiene

  11. Noise Control • Barriers • Distance • Isolation Industrial Hygiene

  12. Limits • 84 dBA 8 hours AF/DOD (4 dB) • 90 dBA 8 hours OSHA (5dB) • 85 dBA 8 hours TLV (3dB exhange) See Chapter 21, page 445 See TLV booklet page 117. Industrial Hygiene

  13. Limits 5 dBA exchange Rate • 90 dBA for 8 hours • 95 dBA for 4 hours • 100 dBA for 2 hours What is the limit for 30 minutes? Industrial Hygiene

  14. Distance • If a noise source is 96 dBA at 10 feet • What is the intensity at 20 feet? Industrial Hygiene

  15. Distance • Answer: 90 dBA • Calc: L =L- 20 Log(D2/D1) L = L -20 Log (20/10) L = L- 20 Log (2) L = L-20 (0.301) L = 96dbA - 6.01 dB = 90dBA Rule of Thumb: Double distance, drop 6 dB Industrial Hygiene

  16. Noise Calc - Activity • A noise source is 102 dBA (Measured) at • 25 feet. What will the noise level be at 60 feet? Industrial Hygiene

  17. Activity • L = 20 Log(D2/D1) • L = 20 Log (60/25) • L =20 Log(2.4) • L = 20 (0.38) • 7.6 dB • 102 dBA – 7.6 dBA = 94.4 dBA Industrial Hygiene

  18. Controls • Turn the Noise Source • Place Barriers (Frequency dependant) • Isolation/Absorption materials Industrial Hygiene

  19. Industrial Hygiene

  20. Industrial Hygiene

  21. Industrial Hygiene

  22. Industrial Hygiene

  23. General Notes • Lower Frequencies more difficult • Specialized materials Industrial Hygiene

  24. Hearing Exposure Effects: • Tinnitus – Ringing, buzzing, whistle • Indicator of damaging noise exposure • Acoustic Trauma – loss due to a sudden intense noise (Explosion) • Threshold Shift – change in the response of hearing in certain frequencies Industrial Hygiene

  25. Noise Induced Hearing Loss Industrial Hygiene

  26. Hearing Loss, Sources Industrial Hygiene

  27. Hearing Loss – Noise Induced Hearing Loss (NIHL Industrial Hygiene

  28. Rules of Thumb • Shout at 3 Feet • Loud Voice at 1 foot • It’s Hazardous Noise! Industrial Hygiene

  29. Speech Interference Level • SpIL = Limit to 55 dBA background • Difficulty using phones, communicating Industrial Hygiene

  30. Noise Measurement • Hand-held • Octave Band Analysis • Graphic Level Instruments Industrial Hygiene

  31. Moving the Source • rotation Industrial Hygiene

  32. Medical Examinations • Baseline • Periodic • Annual • 48 hours noise free • Threshold shifts Industrial Hygiene

  33. Medical Examinations • Threshold shift determination is • Frequency Dependant • Age factors • smoking Industrial Hygiene

  34. Noise Control • Hearing Protection 27 dBA 19-23 dbA 18-23 dBA Industrial Hygiene

  35. Noise Control 27 –33 dBA reduction Industrial Hygiene

  36. Noise Control Industrial Hygiene

  37. Noise Control • Noise Source: 117 dBA, 2 hours • V51Rs • Noise Exposure:? Industrial Hygiene

  38. Noise Exposure • 117-27 dbA = 90 dBA • Adequate? • In some cases, have to use plugs and muffs! Industrial Hygiene

  39. Vibration • Human exposure divided into: • Whole Body • Hand-arm vibration Industrial Hygiene

  40. Vibration • Causes: • Vibration induced White Finger (VWF) or • Raynauld’s syndrone Industrial Hygiene

  41. Vibration • Exposure: (Book) • 8 Million workers Industrial Hygiene

  42. Vibration - Charts Industrial Hygiene

  43. Vibration Duration m/s2 gDelta 4 Hrs < 8 hrs 4 0.40 g 2 hrs < 4 hrs 6 0.61 1 hr < 2 hrs 8 0.81 < 1 hr 12 1.22 G = 9.81 m/sec > 16 hz may need special consideration! Industrial Hygiene

  44. Variations: • UK 2.8 m/sec 8 hours • Canada Same. Industrial Hygiene

  45. Average Vibration • Average Vibration: 9.0 m/sec2 -Jackhammer (Time Limit?) Industrial Hygiene

  46. Average Vibration • After Training/Techniques: • 5.5 m/sec2 Industrial Hygiene

  47. ELV = Exposure Limit Value EAV = Exposure Action Value Industrial Hygiene

  48. Hand Direction Industrial Hygiene

  49. Stage Assessment Table Industrial Hygiene

  50. Industrial Hygiene

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