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

Questions?

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

Questions?