1. Rensselaer Environmental Noise Architectural Acoustics II March 17, 2008

2. Rensselaer Outline Barriers  Basic insertion loss  Location relative to S and R  Edge geometry Source and receiver conditions  Close vs. far  Moving vs. stationary Distance effects  Ground cover  Grazing incidence  Temperature inversions Traffic and railroad noise

3. Rensselaer Sources/Resources Long, Architectural Acoustics J. Foreman, Sound Analysis and Noise Control, Van Nostrand Reinhold, 1990. Kurze and Anderson, “Sound Attenuation by Barriers,” Appl. Acoust. 4, 35 (1971). S. Ho et al., “Noise reduction by a barrier having a random edge profile,” JASA 101 (5) 1997. Z. Maekawa, ‘‘Noise reduction by screens,’’ Appl. Acoust. 1, 157, 1968. D. N. May and N. M. Osman, “Highway noise barriers: new shapes,” J. Sound. Vib. 73 (1), 1980. Berkhoff, “Control strategies for active noise barriers using near-field error sensing,” JASA 118 (3), 2005.

4. Rensselaer Noise Barrier Performance http://www.ashraeregion7.org/tc26/pastprograms/Outdoor_Noise/barriers.pdf

5. Rensselaer Math Review Hyperbolic tangent: -2π-π-π0π2π2π

6. Rensselaer Barrier Geometry S R b a d θ Fresnel Number: S = source d = source-to-receiver distance R = source a + b = shortest path from S to R over the barrier θ = angle between and the barrier normal Kurze and Anderson, “Sound Attenuation by Barriers,” Appl. Acoust. 4, 35 (1971). Barrier

7. Rensselaer Barrier Insertion Loss Kurze and Anderson, “Sound Attenuation by Barriers,” Appl. Acoust. 4, 35 (1971). Assumptions  S is a point source  No sound is transmitted through the barrier  The barrier is infinitely long  Ground reflections and other secondary propagation paths are negligible

8. Rensselaer Theoretical Barrier Performance for a Point Source What does the increasing trend with N suggest about the optimal placement of a barrier given the source and receiver positions?

9. Rensselaer Theoretical Barrier Performance for a Line Source Integrate the point-source IL equation R Barrier Line Source

10. Rensselaer Comparison of Point Source and Line Source IL Foreman, Sound Analysis and Noise Control, Figure 4.28, p. 104.

11. Rensselaer Comparison with Measurements Ho et al., “Noise reduction by a barrier having a random edge profile,” JASA 101 (5) 1997.

12. Rensselaer Homework Assignment Come up with a new barrier design Explain why you think it will out-perform a standard barrier Due Thursday 3/27

13. Rensselaer Jagged-Edge Barriers Ho et al., “Noise reduction by a barrier having a random edge profile,” JASA 101 (5) 1997. “…the edge [at the top of a noise barrier] acts as a line source. For the traditional straight-edge barrier, the line source is coherent. Since a crooked line source is less coherent, we propose to improve barrier performance by making the edge randomly jagged.”

14. Rensselaer Jagged-Edge Barriers Ho et al., “Noise reduction by a barrier having a random edge profile,” JASA 101 (5) 1997. Improved performance at high frequencies, worse at low frequencies. Why?

15. Rensselaer Other Barrier Designs D. N. May and N. M. Osman, “Highway noise barriers: new shapes,” J. Sound. Vib. 73 (1), 1980. 53.5 2 5 X Reported broadband increase in IL (dBA) over a straight-edge barrier

16. Rensselaer Other Barrier Designs D. N. May and N. M. Osman, “Highway noise barriers: new shapes,” J. Sound. Vib. 73 (1), 1980. 2.5 X Reported broadband increase in IL (dBA) over a straight-edge barrier

17. Rensselaer Other Barrier Designs And THNAD is for Thnadners And oh, are they sad, oh! The big one, you see, has the smaller one's shadow. The shadow the small Thnadner has should be his. I don't understand it, but that's how it is. A terrible mix-up in shadows! Gee-Whizz!

18. Rensselaer Absorptive Barrier Surfaces Long, Architectural Acoustics, Figure 5.9, p. 167

19. Rensselaer Absorptive Barrier Surfaces Long, Architectural Acoustics, Figure 5.10, p. 168

20. Rensselaer Active Barriers: Theory Berkhoff, “Control strategies for active noise barriers using near-field error sensing,” JASA 118 (3), 2005.

21. Rensselaer Active Barriers: Experiment Berkhoff, “Control strategies for active noise barriers using near-field error sensing,” JASA 118 (3), 2005. Barrier Microphone Array Sources

22. Rensselaer Active Barriers: Simulation Results Berkhoff, “Control strategies for active noise barriers using near-field error sensing,” JASA 118 (3), 2005.

23. Rensselaer Environmental Effects Air absorption due to  Viscosity  Thermal conductivity  Molecular relaxation Sources of energy loss

24. Rensselaer Environmental Effects Air absorption

25. Rensselaer Environmental Effects Excess attenuation in forests  f = frequency  r = distance through the forest Grazing attenuation  Reflection of sound from a soft surface at shallow angles (close to parallel incidence) often results in a phase shift  The reflection destructively interferes with the direct sound to cause excess attenuation  This also occurs in concert halls with grazing incidence sound over audience seats. The attenuation is known as “seat dip”.

26. Rensselaer Environmental Effects Long, Architectural Acoustics, Figures 5.20 and 5.21, p. 178 Wind velocity increases upward

27. Rensselaer Truck Noise Long, Architectural Acoustics, Figures 5.28, p. 189

28. Rensselaer Truck Noise Long, Architectural Acoustics, Figures 5.29, p. 190

29. Rensselaer Car Noise Long, Architectural Acoustics, Figures 5.30, p. 190

30. Rensselaer Train Noise Long, Architectural Acoustics, Figures 5.32, p. 191

31. Rensselaer Train Noise Long, Architectural Acoustics, Figures 5.36, p. 195

32. Rensselaer Train Noise Long, Architectural Acoustics, Figures 5.37, p. 195

33. Rensselaer Aircraft Noise