noise mitigation - barrier to mitigate noise in exterior recreation areas: ＞ rearrange site...

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)

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

NOISE MITIGATION - BARRIER

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

NOISE MITIGATION - BARRIER

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

Follow calculations in Noise

Guidebook Workchart 5

NOISE MITIGATION - BARRIER

Refer to Workchart 6 and Workchart 7 in guidebook as directed by

Workchart 5 to complete evaluation

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

Questions?