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Chapter 8 Introduction to Environmental Engineering

Chapter 8 Introduction to Environmental Engineering. 4 th Edition Mackenzie L. Davis And David A. Cornwell. Noise Pollution. Fig 8-3 : Relative scale of sound pressure levels. Three SPL’s 68 db, 79 dB and 75 dB. What is SPL of combination?. = 7. 68 dB. 75.8 dB. 75 dB.

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Chapter 8 Introduction to Environmental Engineering

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  1. Chapter 8Introduction to Environmental Engineering 4th Edition Mackenzie L. Davis And David A. Cornwell

  2. Noise Pollution

  3. Fig 8-3: Relative scale of sound pressure levels

  4. Three SPL’s 68 db, 79 dB and 75 dB What is SPL of combination?

  5. = 7 68 dB 75.8 dB 75 dB

  6. Fig 8-4: Graph for solving decibel addition problems

  7. 75.8 dB 80.7 dB  = 3.2 79 dB

  8. MEASURING SPL • Type II sound Level Meter • Weighting Scales: A, B, C • Octave Band Analysis • Narrow Band

  9. TYPES OF NOISE Continuous Uninterrupted, varies less than + 5 dB Intermittent Continuous noise for > 1 sec Interrupted for > 1 sec Impulsive (Impulse) Change SPL> 40 dB in less than .5 sec Duration < 1 sec

  10. Fig 8-11: Cross section through the cochlea

  11. Fig 8-16: Various degrees on injury to hair cells

  12. Fig 8-14: An audiogram illustrating excellent hearing response

  13. Fig 8-17: An audiogram illustrating hearing loss at high frequency notch

  14. Fig 8-19:NIOSH occupational noise exposure limits for continuous or intermittent noise exposure

  15. INVERSE SQUARE LAW

  16. IN TERMS OF SOUNDPRESSURE Lp = Lw - 20 log r - 11 Where 20 log r = 10 log r2 11= 10 log 4

  17. DIRECTIVITY INDEX DI = Lp - Lps

  18. INVERSE SQUARE LAWWITH DIRECTIVITY Lp = Lw + DI - 20 log r - 11

  19. BASIC POINT SOURCEMODEL Lp = Lw - 20 log r - 11 -Ae

  20. EXCESS ATTENUATION Ae1 = attenuation by absorption in air, dB Ae2 = attenuation by ground, dB Ae3 = attenuation by barriers, dB Ae4 = attenuation by foliage, dB Ae5 = attenuation by houses, dB

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