HomeMy WebLinkAboutCT 16-09; 800 GRAND AVENUE; NOISE STUDY; 2016-11-11"\..A Veneklasen Associates v~ Consultants in Acoustics I Noise I Vibration I AV I IT
November 11, 2016
McKellar McGowan
888 Prospect Street, Suite. 330
La Jolla, California 92037
Attention: Mr. Jeff Johnson
Subject: 800 Grand
Carlsbad, California
Exterior Fa~ade Acoustical Design
VA Project No. 6697-001
Dear Jeff:
Veneklasen Associates (VA) has completed our review of the 800 Grand project located in Carlsbad, California.
This report represents the results of our findings.
1.0 INTRODUCTION
This study was conducted to determine the impact of the exterior noise sources on the 800 Grand
project in Carlsbad, California. VA's scope of work included calculating the exterior noise levels
impacting the site and determining the method, if any, required to reduce the interior and exterior
sound levels to meet the applicable code requirements of the State of California and the City of
Carlsbad.
The project consists of a residential development. The project is bounded by Grand Avenue to the
south, Home Avenue to the north, and existing residential or commercial buildings to the east and
west. 1-5 freeway is approximately 950 feet to the east.
2.0 NOISE CRITERIA
CNEL (Community Noise Equivalent Level) is the 24-hour equivalent (average) sound pressure level in
which the evening (7 pm-10 pm) and nighttime (10 pm - 7 am) noise is weighted by adding 5 and 10
dB, respectively, to the hourly level. Since this is a 24-hour metric, short-duration noise events (truck
pass-by's, buses, trains, etc.) are not as prominent in the analysis.
Leq (equivalent continuous sound level) is defined as the steady sound pressure level which, over a
given period of time, has the same total energy as the actual fluctuating noise.
2.1 Interior Noise Levels -Residential
The State of California Building Code (Section 1207, "Sound Transmission") and the City of Carlsbad
Noise Element state that interior CNEL values for residential land uses are not to exceed 45 CNEL in
any habitable room.
If the windows must be closed to meet an interior level of 45 CNEL, then a mechanical ventilating
system or other means of natural ventilation shall be provided.
2.2 CALGreen -Non-residential
Section 5.507.4.2 of the 2013 California Green Building Code stipulates that for buildings exposed to a
noise level of 65 dB or more when measured as a 1-hour Equivalent Sound Level (Leq), the building
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~ Veneklasen Associates 800 Grand; Carlsbad, CA
Exterior Fa~ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 2
fa~ade, including walls, windows, and roofs, shall provide enough sound insulation so that the interior
sound level from exterior sources does not exceed 50 dBA during any hour of operation. This applies
to non-residential spaces such as leasing and amenities.
2.3 Exterior Noise Levels -Residential
The City of Carlsbad Noise Element state that exterior CNEL values for residential land uses are not to
exceed 60 CNEL in outdoor activity areas.
3.0 EXTERIOR NOISE ENVIRONMENT
3.1 Road Noise Sources
The 2035 Noise Contours were provided for the major roadways in the city. The project site is located
at approximately CNEL 62-63 due to noise from 1-5. Per the traffic count information found on the
Carlsbad website, both Grand Avenue and Home Avenue have less than 8000 vehicles a day, which
does not contribute to the effect of the 1-5 CN EL.
3.2 Overall Exterior Exposure
The City of Carlsbad Noise Element state that exterior CNEL values for residential land uses are not to
exceed 60 CNEL in outdoor activity areas.
3.3 Exterior Noise
Outdoor activity areas are interior to the site, Calculations completed show the reduction of the
building shielding results in sound levels which are less than 60 CNEL meeting the City of Carlsbad
requirements.
4.0 INTERIOR NOISE CALCULATION
4.1 Exterior Facade Construction
VA has assumed that the exterior wall will consist of 3-coat stucco over sheathing on wood studs with
a single layer of gypsum board on the interior and batt insulation in the cavity.
VA's calculations included the roof path, but this was insignificant in the interior noise level calculated.
VA utilized the glazing ratings (glass, frame and seals) shown in Appendix I.
4.2 Interior Average Noise Level (CNEL) -Residential
VA calculated the interior level within the residential units given the measured noise environment and
the exterior facade construction described above.
Where the noise level does not exceed 60, sound rated assemblies are not required. This site is just
above this minimum sound level. VA recommends specifying a window with a minimum rating of STC
28 to maintain a level of acoustical quality across the site.
4.3 Mechanical Ventilation Requirement -Residential
Because the windows and doors must be kept closed to meet the noise requirements, mechanical or
other means of ventilation can be considered for the majority of the units, excluding courtyard facing
units. The ventilation system shall not compromise the sound insulation capability of the exterior
facade assembly.
\
~ Veneklasen Associates
800 Grand; Carlsbad, CA
Exterior Fa~ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 3
4.4 CALGreen -Non-Residential
The CNEL is less than 65 at all amenity and non-residential locations meaning no sound rated
assemblies are required since a study is not required.
5.0 SUMMARY
The following summarizes the acoustical items required to satisfy the noise criteria as described in this
report for 800 Grand.
• Exterior areas of the property comply with the City requirements.
• Non-residential locations do not have a sound level suitably high to trigger CALGreen so there
are no requirements.
• Exterior wall assembly is acceptable as described in Section 4.1.
• The roof assembly was included in our calculations and is not a significant path of sound and
can remain as designed.
• Windows and glass doors with minimum STC 28 and defined in Appendix I are required.
• Residential Mechanical ventilation, or other means of natural ventilation, can be considered
for all units.
Various noise mitigation methods may be utilized to satisfy the noise criteria described in this
report. Alteration of mitigation methods that deviate from requirements should be reviewed by the
acoustical consultant.
If you have any questions or comments regarding this report, please do not hesitate to contact us.
Sincerely,
Veneklasen Associates, Inc.
Cathleen Novak
Associate
John Loverde
Principal
~ Veneklasen Associates
APPENDIX I -GLAZING REQUIREMENTS
800 Grand; Carlsbad, CA
Exterior Fa<;ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 4
In order to meet the predicted interior noise levels described in Section 4.0, the glazing shall meet the
following requirements:
Table 1-Acoustical Glazing Requirements: Minimum Octave Band Transmission Loss and STC Rating
".Mio .... ··
\:STE'
The transmission loss values in the table above can likely be met with the following glazing assemblies:
1. STC 28: 1/8" monolithic -3/4" airspace -1/8" monolithic
However, it should be noted that an assembly's frame and seals may limit the performance of the
overall system. The assemblies given above are provided as a basis of design, but regardless of
construction, the octave band transmission loss of the particular system selected must meet the
minimum values in the table above. Similarly, it is permissible to use an alternate assembly
construction if it meets the transmission loss requirements. Note that the systems shall not be
selected on the basis of STC rating alone.
Independent laboratory acoustical test reports should be provided for review by the design team to
ensure compliance with glazing acoustical performance requirements. Lab shall be a member of the
NVLAP program for accreditation. Lab reports shall be in compliance with ASTM standard E90 and be
no more than 10 years old (from date of submission on specific project). The tests shall be performed
on the entire assembly, including frame and seals. If test reports are not available for the assembly,
VA would require that the assembly be tested at a third party independent lab accredited through
NVLAP for the ASTM E90.
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~ Veneklasen Associates
800 Grand; Carlsbad, CA
Exterior Fa~ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 5
APPENDIX II -GLOSSARY OF ACOUSTICAL TERMS
Absorption
A-weighting (dBA)
Definition
A property of material referring to how much sound it absorbs (as
opposed to reflecting). In the context of this report, absorption refers
to the total quantity of absorption within the receiving space.
Absorption is measure in sabins.
The sound pressure level in decibels as measured in an A-weighting
filter network. The A-weighting de-emphasizes the low frequency
components of the sound in a manner similar to the frequency
response of the human ear and correlates well with subjective
reactions to noise.
Decibel (dB) A unit describing the amplitude of sound equivalent to 20 times the
logarithm, to the base 10, of the ratio of the pressure of the sound to
the reference pressure of 20 µPa. Used to quantify sound pressure
levels.
Equivalent Sound Level (Leq) The time-weighted average noise level during the stated measurement
period.
Sabin A unit used to describe absorption within a space. One sabin is equal
to the absorption of a one-square-foot open window.
Sound Pressure Level (SPL) The amplitude of sound when compared to the reference sound
pressure level of 20 µPa. SPL is measured in dB.
Sound Transmission Class (STC) A single-number metric used to describe the transmission loss
performance of a material or assembly across the frequency spectrum.
It is intended for use primarily when speech is the noise source.
Transmission Loss (TL) A measure of the reduction in sound level as a sound wave passes
through a material. The higher the transmission loss, the better the
material's sound insulating properties.
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"\I\-Veneklasen Associates
APPENDIX Ill -ACOUSTICAL CALCULATION METHODS
Decibel Addition
800 Grand; Carlsbad, CA
Exterior Fa~ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 6
Decibels are based on a logarithmic scale; defined as the logarithmic ratio between a measured sound pressure
level and a reference sound pressure level. When decibels are added, they are not combined arithmetically,
but logarithmically. Decibels are added according to the following equation.
Where:
SPL101 = Total Sound Pressure Level (dB or dBA)
SPL1, SPL2 = Sound Pressure Level 1, 2 (dB or dBA)
A-Weighting
A-weighting a spectrum is completed by applying standardized weighting factors to a frequency spectrum,
either in octave bands or third-octave bands. These resultant A-weighted levels are summed using decibel
addition to generate the overall A-weighted level, noted as dBA. In a report, spectral data is typically presented
un-weighted, and the overall level is presented with A-weighting.
The octave band A-weighting correction factors are shown in the table below:
Octave Band Center Frequency (Hz)
63 I 125 I 250 I 500 I 1000 I 2000 I 4000 I Booo
A-weighting Correction Factor (dB) -26 I -16 I -9 I -3 I 0 I +l I +l I -1
Acoustical Shielding
The presence of adjacent buildings or facades, changes in terrain, parapets, and other similar barriers provide
acoustical shielding, reducing the sound level incident on the exterior facades. Common locations where
acoustical shielding occurs include, but are not limited to, the roof, the back, and sides of the building that are
not directly facing the noise source.
Acoustical shielding due to building geometry can be separated into two categories: reduction due to reduced
area of exposure (side of a building), and shielding from barriers (such as a parapet or sound wall).
Reduction as a result of reduced area of exposure is calculated according to the following equation:
(8exp) llSPL = 10 log10 t80
Where:
llSPL = Change in Sound Pressure Level (dB)
Sexp = Angle of exposure (degrees)
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~ Veneklasen Associates
800 Grand; Carlsbad, CA
Exterior Fa~ade Acoustical Design; VA Project No. 6697-001
November 11, 2016-Page 7
Acoustical Attenuation due to Distance
Sound pressure level reduction due to distance is calculated according to the following equation:
SPL2 = SPL1 + C5log (~:)
Where:
SPL1 = Sound Pressure Level at Location 1 (dB or dBA)
SPLi = Sound Pressure Level at Location 2 (dB or dBA)
Cs= Source Coefficient; 20 for point source, 10 for a line source
r1 = Location 1 distance from source (ft.)
r2 = Location 2 distance from source (ft.)
In some situations, the Cs value is between 10 and 20; selection of this number is an engineering judgment
based on the relationship between the source and receiver as well as the type of source.
Interior Noise Calculation
The interior noise calculation takes into account the exterior noise level, the transmission loss of the glazing
(including glass, frame, and seals), wall, and roof/ceiling systems, the finishes within the space, and noise
exposure due to building geometry and acoustic shielding. The interior sound level is calculated using the
equation:
SPL1 = SPLE + 10 log10(A) -10log10(R) -TL+ 6
Where:
SPL1 = the Interior Sound Pressure Level (dB or dBA)
SPLE = Exterior Sound Pressure Level (dB or dBA)
A= Surface Area exposed to Exterior Noise (sq.ft.)
R = Room Absorption Coefficient (sabins)
TL= Sound Transmission Loss of Exterior Fa~ade Assembly (dB)
This calculation is performed for each exposed fa~ade individually. The total interior sound level is found by
using decibel addition to sum the sound level from all exposed facades.
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