NOISE ANALYSIS
description
Transcript of NOISE ANALYSIS
NOISE ANALYSIS
Airports not
close enough
to have a
significant
impact
SITE ACCEPTABILITY STANDARDS
RATING DNL IN DB REQUIREMENTS
Acceptable Not exceeding 65 dB None
Normally Unacceptable
Above 65 dB but not exceeding 75 dB Special approvals
Unacceptable Above 75 dBAttenuation
Special approvalsEnvironmental review
SITE ACCEPTABILITY STANDARDS
Normally Unacceptable Zone:
> 5 dB additional attenuation (above the expected 20 dB) for sites
with up to 70 dB DNL
> 10 dB additional attenuation for sites with up to 75 dB DNL
> Includes major rehabilitations and conversions
SITE ACCEPTABILITY STANDARDS
Unacceptable zone:> HUD actively encourages conversion to non-noise-sensitive uses
in this zone. Funding requires specific approval by HUD and
may require an Environmental Impact Statement
> EIS Waiver for projects in unacceptable noise conditions
• Noise is the only environmental issue
• There are no outdoor noise-sensitive uses (patios, picnic
areas, balconies, etc.)
• Assurances of pre-occupancy mitigation of other issues
NOISE MITIGATION - ATTENUATION
Because building materials absorb sound, they can
attenuate, or reduce, the level of sound coming into an
area from outside, mitigating the effects of the noise level
> Interior noise-sensitive uses (goal of 45 dB)
> HUD assumes that “typical” construction methods and ratios of
walls to doors and windows will result in a baseline attenuation
of 20 dB
NOISE MITIGATION - ATTENUATION
To increase the amount of attenuation of a wall system
(walls plus windows plus doors), increase the thickness of
the wall components and the density of the materials used
and decrease the connections between layers of the wall
> Supplement to Chapter 4 of Noise Guidebook provides STC
ratings of example walls, windows and doors
NOISE MITIGATION - ATTENUATION
Walls:> From siding to brick or stucco
> Add or increase insulation
> From 4” studs to 6” studs
> Add resilient channels to hang
drywall
> Add an air space between layers
> Avoid penetrations in direction of
noise source
Doors:> From hollow-core to solid-core
> From wood to insulated steel
> Decrease size of glass inserts
> Add specialized seals
Windows:> Add storm windows
> Add a layer of glass
> Add specialized seals
NOISE MITIGATION - ATTENUATION
An architect should be able to provide an estimate of the sound
transmission class (STC) of each part of the wall system – wall,
windows and doors – and the percentage of wall area each occupies
HUD offers an online Sound Transmission Classification
Assessment Tool (STraCAT), but at present windows and doors
cannot be customized to match field conditions, so usefulness is
limited.
NOISE MITIGATION - ATTENUATION
Aside from STraCAT, options to calculate noise
attenuation of selected building materials:
> Figure 17, STC graph, of HUD Noise Guidebook
> HUD Sound Transmission Class spreadsheet, available
upon request
NOISE MITIGATION - ATTENUATION
For sample site, architect reported the following:
> STC of walls = 50 dB
> STC of windows = 26 dB
> STC of doors = 27 dB
> Two walls analyzed:
• Wall 1: 73% wall, 27% windows, no doors
• Wall 2: 93% wall, 2% windows, 5% doors
NOISE MITIGATION - ATTENUATION
To use Figure 17> Subtract STC of windows from
STC of doors
> Enter graph on vertical axis at
resulting number
> Cross to the line representing
percentage of wall taken up by
windows
> Drop down to horizontal axis
> Subtract resulting number from
wall STC to get final STC
NOISE MITIGATION - ATTENUATION
Alternative: spreadsheet