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Principles of Noise GCA Safety Committee March 22, 2005 Susan Geier Fahmy, CSP, CCC-A Lovell Safety Management Co., LLC 1 “Vision relates people to nature. Sound relates humans to each other.” 2 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 3 Health Effects Attributed to Excessive Exposure to Noise Elevated blood pressure Irritability Fatigue Vasoconstriction of peripheral blood vessels Sore throat Gastrointestinal disorders Headaches Allergic reactions Sleeping disorders Damage to the brain stem 4 Sources of Noise Motor vehicles Home Air traffic Laundromats Entertainment Power tools People Emergency vehicles Animals Restaurants And….. 5 Construction Sites Noise… Unwanted sound 7 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 8 Properties of Sound Frequency (Pitch) Intensity (Loudness) 9 Frequency - Pitch # of cycles a wave passes by a point in space per unit of time Cycles/ second or Hertz (Hz) 10 Intensity The Height of the Wave Sound Pressure Level – Decibel 11 How Do We Hear? Outer Ear Middle Ear Inner Ear 12 The Inner Ear Sensori Neural Hearing Loss Noise Induced Hearing Loss 13 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! 14 How Do We Measure All of This? Measuring Pitch (Frequency) Hertz or Cycles Per Second 15 Measuring Loudness Measure intensity or sound pressure Pressure = force/ area Unit of pressure is measured in “Pascals” 0.00002 Pascals 100,000 pascals 16 The Decibel Means Nothing Without a Reference dB SPL – Sound Pressure Level dB HTL – Hearing Threshold Level 20 micropascals = 0 dBSPL Frequency Dependent dB A Mimics Human Hearing db C Mimics Flat SPL 17 ‘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 18 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 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 20 21 Common Noise Levels - dBSPL Barely Audible Watch Ticking Street With out Traffic Normal Conversation Heavy truck Pneumatic chipper Typical Rock Concert Jet Engine (800 ft away) Jackhammer 10 dB 20 dB 40 dB 60 dB 90 dB 100 dB 100 dB 120 dB 120 dB Noise Levels for Common Tools Task/Tool 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 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 Path Control Sound reduction by distance Sound level is reduced 6 dBSP for • each doubling of distance from noise source 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 35 36