CE 453 Lecture 7 Noise Analysis See http

CE 453 Lecture 7 Noise Analysis See: http: //www. nonoise. org/library/highway/probresp. htm and http: //www. fhwa. dot. gov/environment/noise/index. htm and http: //www. fhwa. dot. gov/environment/audible/contents. htm

Noise n n What is noise? Who decides? news. bbc. co. uk www. stedmundsbury. gov. uk sprott. physics. wisc. edu/fractals/ chaos www. plu. edu/scene/issue/ 1999/summer/img 2

Noise n n n Undesirable or unwanted sound Subjective Impacts n n n Annoyance, disturbance Stress Physical and psychological damage 3

Transportation Noise n n Decreases with increasing distance – a corridor problem Generated by: n n Engine Exhaust Aerodynamic friction Interaction between tire-pavement 4

Control of Transportation Noise n Federal -- Noise control act of 1972 n n n Recognized noise as a major degrader of urban living Encourage use of noise standards State and local governments n Also institute noise control 5

Noise Measurement n n n Intensity of a single sound is measured on a relative of logarithmic scale Uses a unit called a bel (B) or subunit – decibel (d. B) At 14 bels, sound is painful to human ear 6

Common Sounds 7

Noise Propagation n n Noise is generated at source and spreads spherically away from source Intensity diminishes with distance Losses also occur from sound energy being dissipated as sound is transferred by air particles Bending and diffraction occurs as sound waves encounter natural and manufactured solid objects 8

Noise Control Strategies n Minimize noise levels n Source controls n Vehicle control devices – maintenance, traffic and highway design controls n Path controls n Sound barriers that reflect and diffuse noise n Buffer zones n Receiver-side controls n insulation 9

Noise abatement measures n n n Traffic management (see next slide) Buffer zones Vegetation Noise insulation Relocating the highway 10

Traffic management measures n Prohibit trucks Truck routes Prohibit daytime (or night-time) use Traffic signal timing Speed limits n Will all these work? n n 11

Noise Source http: //www. nonoise. org/library/highway/traffic. htm 12

http: //www. nonoise. org/library/highway/traffic. htm 13

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Paths: Effects of distance And adding sources http: //www. nonoise. org/library/highway/traffic. htm 15

Receivers: Perceptions of noise http: //www. nonoise. org/library/highway/traffic. htm 16

Number of people annoyed At different sound levels 17

http: //www. nonoise. org/library/highway/policy. htm 18

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What are L 10 and Leq? L 10 is usually about 3 d. B greater than Leq http: //www. nonoise. org/library/highway/traffic. htm 22

What are L 10 and Leq? The equivalent sound level is the steady- state, A-weighted sound level which contains the same amount of acoustic energy as the actual time-varying, A-weighted sound level over a specified period of time. If the time period is 1 hour, the descriptor is the hourly equivalent sound level, Leq(h), which is widely used by SHAs as a descriptor of traffic noise. An additional descriptor, which is sometimes used, is the L 10. This is simply the A-weighted sound level that is exceeded 10 percent of the time. http: //www. nonoise. org/library/highway/policy. htm#II 23

State of the Art is FHWA’s Traffic Noise Model (TNM) n n n n n Modeling of five standard vehicle types, including automobiles, medium trucks, heavy trucks, buses, and motorcycles, as well as user-defined vehicles. Modeling of both constant-flow and interrupted-flow traffic using a 1994/1995 fieldmeasured data base. Modeling of the effects of different pavement types, as well as the effects of graded roadways. Sound level computations based on a one-third octave-band data base and algorithms. Graphically-interactive noise barrier design and optimization. Attenuation over/through rows of buildings and dense vegetation. Multiple diffraction analysis. Parallel barrier analysis. Contour analysis, including sound level contours, barrier insertion loss contours, and sound-level difference contours. Available for $695 at Mc. Trans http: //mctrans. ce. ufl. edu/ 25

Example Problem 2280 120 60 Problem: Find d. BA L 10 • 500 ft from road • 2 lane road • 2400 vehicles per hour • 5 percent trucks • 60 mph #cars =. 95 x 2400=2280 26

Problem: Find d. BA L 10 at 500 ft From a 2 lane road carrying: 2400 vehicles per hour 5 percent trucks, at 60 mph … cars =. 95 x 2400=2280 L d. BA for cars at 100’ = 68 d. BA 27

2280 120 60 68 28

20 30 40 50 60 70 Problem: Find d. BA L 10 at 500 ft From a 2 lane road carrying: 2400 vehicles per hour 5 percent trucks, at 60 mph … trucks =. 05 x 2400=120 L 50 d. BA for trucks at 100’ = 62 d. BA 29

2280 120 60 68 62 30

Problem: Find d. BA L 10 at 500 ft From a 2 lane road carrying: 2400 vehicles per hour 5 percent trucks, at 60 mph … O-ELD = 500’ 31

Problem: Find d. BA L 10 at 500 ft From a road carrying: 2400 vehicles per hour 5 percent trucks, at 60 mph … Adjustment from 100 ft ref = -10 d. B 32

2280 120 60 68 62 -10 33

Problem: Find d. BA L 10 at 500 ft From a road carrying: 2400 vehicles per hour 5 percent trucks, at 60 mph … vol/speed*ELD = 19, 000 for cars, 1, 000 for trucks L 10 - L 50 = 2 d. BA cars, 6. 5 d. BA trucks 34

2280 120 60 68 62 -10 2 6. 5 60 58. 5 35

Adding 2 sources Heavy trucks 58. 5 db Passenger vehicles 60 db 36

Difference = 60 – 58. 5 = 1. 5 Add 2. 3 db to higher 60 + 2. 3 = 62. 3 db due to both sources 37

2280 120 60 68 62 -10 2 6. 5 60 58. 5 62. 3 38

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Noise Barriers 42

Other Adjustments Grade (trucks) n +/- 3 -4% = +2 n +/- 5 -6% = +3 n +/- >7 = +5 Surface n very smooth = -5 (auto only) n very rough = +5 (auto, or truck>60 mph) Interrupted flow (L 10) n auto = +2 n Truck = +4 Foliage n -5 for each 100’ >15’ n -10 max Rows of houses n -5 for each n -10 max 43

Noise Barriers (how they work) Noise is "diffracted" over the barrier, this increases the distance it travel to the listener, thus decreasing the noise A+B>C Source: http: //www. urbislighting. com/uap 1. html 44

Noise Barriers (how they work) Noise is also reflected and/or absorbed Source: http: //www. urbislighting. com/uap 1. html 46

Possible barriers http: //www. nonoise. org/library/highway/traffic. htm 47

http: //www. nonoise. org/library/highway/traffic. htm 48

49 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”

50 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”

51 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”

52 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”

53 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”

54 Source: FHWA, “Keeping the Noise Down, Highway Traffic Noise Barriers”