NOISE MITIGATION - BARRIER

1. NOISE MITIGATION - BARRIER • To mitigate noise in exterior recreation areas: • Rearrange site (potentially provides both distance and barriers) • Put up a noise-specific barrier • If there are existing barriers such as buildings or topographic features between project site and noise source, first evaluate whether they provide sufficient mitigation • Mitigation should be in direction of main noise source(s)

2. NOISE MITIGATION - BARRIER • To be effective, barrier must: • Interrupt line of sight between noise source and receptor • Be continuous, and extend to the ground surface • Be of a material that will absorb sound energy • When considering wooden fences as barriers, incorporate an air space between two continuous fence surfaces to increase effectiveness • Noise Guidebook has Transmission Loss Values for evaluating the relative effectiveness of various materials

3. NOISE MITIGATION - BARRIER

4. NOISE MITIGATION - BARRIER • To evaluate barrier, need to know: • Observer elevation • Noise source elevation • Current and projected noise levels • Elevation of the top of the barrier • Distance, observer to barrier • Distance, barrier to source • Angle subtended by barrier

5. Sample site: Observer elevation: 525 ft Source elevation: 514 ft Current noise level: 71.83 dB Projected noise level: 72.38 dB Barrier top elevation: 546 dB Observer-barrier distance: 141 ft Barrier-source distance: 523 ft Barrier angle: 95 degrees NOISE MITIGATION - BARRIER

7. NOISE MITIGATION - BARRIER • Follow calculations in Noise Guidebook Workchart 5

9. NOISE MITIGATION - BARRIER • Refer to Workchart 6 and Workchart 7 in guidebook as directed by Workchart 5 to complete evaluation

10. NOISE MITIGATION - BARRIER • To improve barrier performance without changing dimensions: • Move closer to observer – increases effective angle of barrier • Angle ends toward observer – also increases effective angle • Angle top toward source – increases effective height of barrier

11. Questions?