Post on 04-Jan-2016
description
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?