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Principles of Noise

Principles of Noise. GCA Safety Committee March 22, 2005. Susan Geier Fahmy, CSP, CCC-A Lovell Safety Management Co., LLC. “ Vision relates people to nature. Sound relates humans to each other.”. Health Effects Attributed to Excessive Exposure to Noise. Lower reading scores

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Principles of Noise

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  1. Principles of Noise GCA Safety Committee March 22, 2005 Susan Geier Fahmy, CSP, CCC-A Lovell Safety Management Co., LLC

  2. “Vision relates people to nature.Sound relates humans to each other.”

  3. Health Effects Attributed to Excessive Exposure to Noise • Lower reading scores • Lower quality of work • disturbs concentration • disruptive • fatigue • aggravation and frustration • Stress - “fight or flight response” • adrenalin surge • heart and breathing rate increases • muscles tense

  4. Elevated blood pressure Irritability Fatigue Vasoconstriction of peripheral blood vessels Sore throat Gastrointestinal disorders Headaches Allergic reactions Sleeping disorders Damage to the brain stem Health Effects Attributed to Excessive Exposure to Noise

  5. Motor vehicles Air traffic Entertainment People Animals Home Laundromats Power tools Emergency vehicles Restaurants And….. Sources of Noise

  6. Construction Sites

  7. Noise… Unwanted sound

  8. What is Sound ? • An oscillation in pressure in a medium (such as air) • The oscillation travels through the medium at a certain speed and magnitude

  9. Properties of Sound • Frequency (Pitch) • Intensity (Loudness)

  10. Frequency - Pitch # of cycles a wave passes by a point in space per unit of time Cycles/ second or Hertz (Hz)

  11. Intensity The Height of the Wave Sound Pressure Level – Decibel

  12. How Do We Hear? • Outer Ear • Middle Ear • Inner Ear

  13. The Inner Ear Sensori Neural Hearing Loss Noise Induced Hearing Loss

  14. Effects of Noise • Sensorineural Hearing Loss • Destruction of hair cells in the cochlea • Outer hair cells (high frequency receptors) are first affected • Continued exposure collapses other hair cells **Damage is initially temporary and then permanent!

  15. How Do We Measure All of This? Measuring Pitch (Frequency) • Hertz or Cycles Per Second

  16. Measuring Loudness Measure intensity or sound pressure • Pressure = force/ area • Unit of pressure is measured in “Pascals” • 0.00002 Pascals 100,000 pascals

  17. The Decibel Means Nothing Without a Reference dB SPL – Sound Pressure Level 20 micropascals = 0 dBSPL dB HTL – Hearing Threshold Level Frequency Dependent dB A Mimics Human Hearing db C Mimics Flat SPL

  18. ‘Normal’ Hearing Frequency Range Intensity: 0 dbHTL – 25 dBHTL Frequencies: 500 Hz - 2 kHz Noise Induced Hearing Loss Loss of high frequency acuity s’s, x’s, f’s difficult to distinguish

  19. Decibels are Logarithmic Cannot Add and Subtract - Are Not Linear Difference between 5 dBSPL and 10 dBSPL DOES NOT EQUAL The Difference between 10 dBSPL and 15 dBSPL

  20. Decibels • Ear responds to logs (dB) as if the sound pressure is a linear increment • Doubling of perceived loudness is approximately a 3 dBSPL increase

  21. Common Noise Levels - dBSPL Barely Audible 10 dBWatch Ticking 20 dBStreet With out Traffic 40 dBNormal Conversation 60 dBHeavy truck 90 dB Pneumatic chipper 100 dB Typical Rock Concert 100 dBJet Engine (800 ft away) 120 dBJackhammer 120 dB

  22. Mortising Orb. Sand. Table Saw Planer Belt Sander Router Metal Shear Hand Drill Circular Saw Tile Saw Impact Wrench Miter Saw Chop Saw Chain Saw Hammer Drill 75 80 85 90 95 100 105 110 115 Noise Levels forCommon Tools Task/Tool

  23. A - Scale (dBA) • Attenuation of low frequencies • Enhances high frequency perception • Human ears attenuate sounds below 1 kHz • We perceive high frequency sounds to be louder than low frequency sounds, though they might have equal sound pressure

  24. Measurement of Sound • Sound Level Meters (type 1 or 2) • Measures continuous sound pressure instantaneously • A scale, slow response • Set to “max” or Lmax (for OSHA/NYC measurements) • Gives instantaneous readout • Measurement done in hearing zone

  25. Noise Dosimeters • Will measure sound levels which are constantly fluctuating • Integrate sound pressure with time • Worn by the worker for the entire shift • Readout indicates percentage of the permissible exposure limit (90 dBA @ 8 hours) to which employee was exposed

  26. Ambient Sound Measurements taken at a comparable site in the nearby area

  27. Noise Control Source Receiver Path

  28. Source Control • Quieter Work Process • Internal damping • Enclose Equipment • Walls with high Transmission Loss • Lead rubber fabric draperies • Noise jackets • Alter/ modify equipment • Internal damping • Mufflers • Prevent/ reduce impact between machine parts • Replace metal parts with plastic parts

  29. Sound level is reduced 6 dBSP for • each doubling of distance from noise source Path Control • Sound reduction by distance • Sound Barriers

  30. Receiver Employee Hearing Protection Reduce time exposed - HCP Increase distance of nearby workers

  31. New York City Noise Code Construction: Work, Device and Material New Definitions: Extraneous Sound: intense, intermittent < 50% of sound source – excluded when measuring sound Impulsive Sound: Each peak of sound lasts < 2 seconds Plainly Audible Sound: does not requirement measurement Unreasonable Noise: >15’ from source; 7dBA over ambient 10 pm–7am; 10dBA over ambient 7am-10pm – Impulse 15dBA over ambient on fast scale - Not Construction!

  32. Construction…. New subchapter (24-219) will be added with new rules prescribing noise mitigation strategies (in addition to those already listed (Perimeter fences, blanket insulation etc.) Noise Mitigation Plan – adopted at beginning of construction After hours work cannot exceed 8dBA over ambient measured inside “residential receiving property”

  33. Subchapter 5 – standards for specific noise sources 24-228 – Construction devices/exhausts >85dBA measured 50’ or more outside property line of source. Impulsive: < 15dBA over ambient 24-229 – Containers and construction material >7dBA over ambient – night >10dBA over ambient – day measured 15’ or more from source >15dBA over ambient – impulsive

  34. 24-230 – Paving breakers Not operated electrically or hydraulically Must have pneumatic discharge muffler

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