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Introduction to Noise Control

Introduction to Noise Control. Environmental Science Ithan B. Zimmer, Ph.D., P.E. Basic Noise Control. Environmental Noise Studies Other Studies: Industrial, Theoretical, Mechanical Environmental Impact Statements (EIS) You need to understand the language You can participate in an EIS

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Introduction to Noise Control

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  1. Introduction toNoise Control Environmental Science Ithan B. Zimmer, Ph.D., P.E.

  2. Basic Noise Control • Environmental Noise Studies • Other Studies: Industrial, Theoretical, Mechanical • Environmental Impact Statements (EIS) • You need to understand the language • You can participate in an EIS • More background means it is harder to fool you

  3. Famous Authors • Leo Beranek (Father of Noise Control) • Cyril Harris (Handbook) • Karl Kryter (Effects) • Charles E. Wilson (NJIT)

  4. Basic Noise Control • Noise = unwanted sound • noise pollution is redundant • wasted energy • What defines noise is subjective • Environmental noise generally is transient

  5. Possible Effects • Hearing Loss • Annoyance – Quality of Life Issues • Physiological Disorders • Psychological Disorders

  6. Noise Measurement • Decibel scale (dB) • Logarithmic, use common log, base 10 log xy = y log x log (xy) = log x + log y log (1/x) = - log x log (x/y) = log x – log y log 1 = 0

  7. Sound Pressure Level (SPL) • SPL (dB) = 20 log (P/P0) • P = rms sound pressure • P0 = reference pressure 20 μPa • Threshold of Hearing = 0 dB • Threshold of Pain = 140 dB

  8. Equation for TotalSound Pressure Level • SPLT = 10·log (10L1/10 + 10L2/10 + … + 10Ln/10) • L1, L2 … are noise measurements in dB • Examples using table or equation

  9. Combining Noise Measurements

  10. Loudness • An average individual perceives an increase in sound level of ~10 dB as a doubling in loudness.

  11. Frequency Weighting • There are multiple weighting systems • A-weighting is, by far, the most common • It is the best for environmental and community applications because it reflects human response. • Abbreviated dBA • Humans hear 20-20,000 Hz • Most sensitive from 500-10,000 Hz • http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/

  12. Metrics – Cumulative Noise Levels • LX – noise level exceeded X% of the time • L10 • L50 – median noise level • L90 – background noise level • Transit/Highway applications

  13. Average over a period of time Equations on the board Day-Night Level: Ldn or DNL An Leq for 24 hours with a 10 dBA penalty for night noise (10pm to 7am) Used in community noise, especially airports Airports must mitigate to below DNL 65 EPA outdoor to DNL 55, indoor DNL 45 Equivalent Sound Level - Leq

  14. Basic Noise Control Elements Source Receiver Path Environmental concern: air path, also structure Sources: surface traffic, trains, aircraft, fans, machinery Receiver: people

  15. Noise Mitigation and Control • Reduce at the Source – almost always the best method • Increase or block the Path • Protect the Receiver

  16. Noise Mitigation and Control • Source: engine design, exhaust control, friction reduction, # of vehicles • Path: noise barrier, increase the path, Land Use Management • Receiver: home treatment, hearing protection • 85 dBA single hearing protection • 104 dBA or 140 dBA pulse double hearing protection

  17. Line Source vs. Point SourceDouble Distance = ? SPL1 – SPL2 = 10 log (r2/r1) SPL1 – SPL2 = 20 log (r2/r1)

  18. Any Questions? • Institute of Noise Control Engineering • www.inceusa.org • Noise Pollution Clearinghouse • www.nonoise.org • Environmental Protection Agency • www.epa.gov

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