La Chateau-PR 990317Pelton Marsh Kinsella
Consultants in Acoustics, Theatre, Television
and Audio/Visual Design
Janua~ 29,1999
Mr. George Hicks
George Hicks Design Consultant
8314 San Cristobal
Dallas, Texas 75218
Ref:
Acoustical Analysis Results
Retirement Residences for Seniors
Coppell, Texas
PMK Project No. 992513010
Dear Mr. Hicks:
An acoustical analysis was performed on the 94 unit retirement residences for seniors to
be built at State and Sandy Lake Road in Coppell, Texas. The purpose of the analysis
was to determine the potential impact of outdoor environmental noise levels upon the
bedrooms and living areas. Results of the analysis along with some recommendations
are discussed below.
The project is to be built near the D/FW International Airport aircraft flight tracks from the
airport. It is in the "high noise zone" created by the aircraft.
The City of Coppell is following the FAA guidelines and requiring an outside to inside
noise reduction in occupied area of the residences of 25 dBA (A-weighted sound
pressure levels in decibels). This is the next to the highest noise zone allowed for
residential use property. In general, the average day-night noise level (DNL or Ld,) zone
of 66 to 70 dBA requires a 25 dBA noise reduction (NR) and the 71 to 75 dBA zone
requires a 30 dBA NR. While there is only a 5 dB variation between the two zones, there
is a relatively vast difference is how to meet the two limits. Normally used "energy
conservation" building means and methods will provide a 20 to 25 dBA of NR. A 25 dBA
NR generally requires better than "normal" construction.
The general guidelines to meet a 25 dBA NR as recommended by the U.S. Department
of Housing and Urban Development (HUD) for residential property are a good place to
start with determining potential construction steps to take. Some general items are as
follows:
1. The exterior walls should have a minimum sound transmission class (STC) of 39.
Windows should have a minimum STC rating of 28. For single pane windows the
glass needs to be at least 3/16" thick or insulated glass window assemblies can
be used.
1420 W. Mockingbird Lane, Suite 400 · Dallas, Texas 75247
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Pelton Marsh Kinsetla is a division of Carter & Burgess, Inc.
Letter to: Mr. George t xs
Dated: January 29, 1999
Page: 2
3. Exterior doors in sleeping areas must have a minimum STC rating of 28 and be
air tight through use of effective perimeter weather-stripping.
4. The total area of windows and exterior doors should not exceed 20% of the
sleeping space floor area.
5. The roof construction should provide at least a STC-39 rating with minimized in
size vents with direct opening to the outside but still meet any code requirements.
6. All sound sensitive areas need to be carpeted.
7. "Through the wall" ventilation units should not be used. Obviously open window
ventilation should not be used.
There was more than one analysis technique used to evaluate the required noise
reduction in the sound critical bedrooms. An attempt was made to "make" the proposed
construction and material selections "work". There is only one typical model with single
story construction, one master bedroom with bath, and a living room attached.
Typical building element constructions was used for the analysis. "Generic" materials
and equipment was assumed. There will be some variations expected from product
brand to brand. High construction standards will be needed to meet the noise reduction
requirements. The only exception is that the use of specific brand windows was
assumed. The Sound Transmission Class (STC) values for the windows were taken from
the copies of the sound transmission loss tests provided by two window manufacturers.
H-R Windows were assumed for the Slider (SLDR) windows with a STC rating of 28,
which is good; and also they have Picture (fixed panels) windows with a STC rating of
30. A Single Hung (SH) window by a local manufacturer such as Skotty Aluminum
Products with a STC rating was 28 was assumed as typical. If other brands are used the
STC ratings are required to be known.
Based upon the available information and my interpretation of the construction
documents and general construction techniques, the building system construction and
materials of concern are as follows:
Exterior Walls: Estimated nominal STC-up to 50 ratin~].
Face brick with airspace is used on all of exterior.
%, thick type insulated sheathing considered.
(with 5/8" gypsum sheathing preferred, see recommendations)
2 by 4 wood studs with R-13 batt insulation and plastic vapor barrier, and
1/2" type "X" sheetrock on intedor
Windows: Estimated at STC-28 rating.
Insulated residence single hung are typical.
There are a few fixed window to complement the above.
The exterior swinging door with glass used in the Living Room would have a similar
rating and is considered with the windows.
...... Pelton Marsh Kinsella
Letter to: Mr. George, ~s
Dated: January 29, 1999
Page: 3
Note: Generally windows are critical item for overall NR.
Roofs: Estimated at up to STC-50 rating.
Spanish tile,
15# felt paper,
1/2" plywood decking,
Pitched roof with attic with soffit vents
Wood joists system,
R-22 or so batt insulation, and
1/2" layer sheetrock directly attached to bottom of joists are typical.
First, "the closer the actual construction is to the guidelines" will provide a closer
assurance that the required NR can be met. Thus some of the parameters were
calculated. The percent of glass area to the floor area is typically 9 to 18% for the
bedrooms with up to 18% used on living room including the exterior door. The amount of
acoustical absorption for the carpeted bedrooms were considered. This noise reduction
can be applied to an expected aircraft noise spectrum (level in dB versus frequency in
Hz) to obtain the dBA NR.
The composite STC and NR were determined for the different sized bedrooms. The
values are provided in the table below.
Room Composite STC NR, dBA Windows/Doors
Living 30 29
two of SH and Door
Bedroom, 1 Window
35 31 one of SH
Bedroom, 2 Windows 32
28 two of SH
In general, the one or two windows bedrooms using the single hung windows with the
STC-28 rating appear to be clearly acceptable. The living room with the indicated
amount of glass in the windows and exterior door is also acceptable. The sound isolation
for the rest of the living areas should be acceptable.
In summary, the analysis has shown that the required noise reductions can be generally
met. Field measurements, which we understand are not presently required by the City of
Coppell, in general can be lower.
The following recommendations are made to met the minimum requirements set by the
City of Coppell. As you are probably aware this minimum 25 dBA NR will significantly
reduce the noise of, for an example, commercial jet single event fly-overs but it could still
be heard by the occupants.
In conclusion, additional noise control treatment will not be required but some careful
selection of building materials will be required. The recommendations provided below are
provided in order to accomplish the required task of providing a outside to inside
environmental noise reduction of 25 dBA.
Letter to: Mr. George ~ xs
Dated: January 29, 1999
Page: 4
Use windows which will seal generally airtight, if operable when closed, or fixed.
Bedroom windows are the most critical and should be tested for a STC-28 minimum
rating. These should be similar to H-R Windows Sedes 350 Insulated Slider, if used,
Windows with a STC-28 rating and Skotty Aluminum Series 775 Insulated Single
Hung Windows with also a STC-28 rating. All other windows in living areas of the
houses should be double pane insulated or single pane with similar STC-28 minimum
ratings.
Use gypsum sheathing with 5/8" thickness preferred, OSB, or plywood instead of
insulating foam type, especially behind the surfaces covered with siding, if used,
instead of face brick.
All exterior doors should be insulated metal, insulated vision panels, or solid wood.
These doors need to have a minimum STC of 28 with around 30 typically expected.
The perimeter of each should be weather-stripped and generally airtight.
4. Minimize attic vents openings in area but still met all codes.
It is recommended that the City of Coppell accept the design with acoustical attributes as
indicated in this letter for construction. The design should meet the required 25 dBA of
outside to inside of environmental noise reduction.
Thank you for contacting us. Please let us know how we may be of further assistance.
We will be glad to Club and Office areas when the design information becomes available.
Sincerely,
PELTON MARSH KINSELLA
Ted N. Carnes, Ph.D., P.E.
Senior Consultant
Cc: Charles Bandemer
~'~ Penton Marsh Kin.nb