HomeMy WebLinkAboutSDP 15-22; QUARRY CREEK PA R-2; EXTERIOR ENVELOPE ACOUSTICAL DESIGN; 2015-08-24"\-A Veneklasen Associates v~ Consultants in Acoustics I AV I IT I Environmental Noise
August 24, 2015
Lennar Multifamily Investors
25 Enterprise, 3rd Floor
Aliso Viejo, California 92656
Attention: Mr. John Colletti
Subject: Quarry Creek
Carlsbad, California
Exterior Envelope Acoustical Design
VA Project No. 5123-008
Dear John:
Veneklasen Associates (VA) has completed our acoustical review of the Quarry Creek Development Site 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 Quarry Creek
Development. VA's scope of work included calculating the exterior noise levels impacting the site and
determining the method required to lower interior sound levels to meet applicable code
requirements. The results of VA's analysis are presented in this report.
The project reviewed consists of a combination of 4 Residential Buildings, 5 Public Use Areas, and 3
Open Spaces; Residential units will total 636. The site will be located in a large undeveloped area just
south of Highway 78. To the east are some commercial properties, up a hill to the south are single-
family home developments. The current development plan is shown in Figure 1.
Figure 1: Development Site
2.0 NOISE CRITERIA
LON is the 24-hour equivalent sound pressure level in which the nighttime noise levels, occurring
between the hours of 10 pm and 7 am, are weighted by adding 10 dB of sound level to the measured
hourly average. Since this is a 24 hour metric, single event noise levels (truck pass-bye, bus, trains,
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Quarry Creek Development -Exterior Envelope Acoustical Design
August 24, 2015
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etc.) are smoothed over the time frame meaning that the single event noise levels are not as
prominent in the analysis.
LAeq (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 from Transportation Sources
The Noise Ordinance of the City of Carlsbad and California Building Code requires that the interior
noise level from transportation noise sources not exceed LON 45 in any habitable room.
If the windows must be closed to meet the interior noise level criteria, then a mechanical ventilating
system or other means of natural ventilation shall be provided.
2.2 CalGreen
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 fai;: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 Amenity or Retail.
3.0 EXTERIOR NOISE ENVIRONMENT
3.1 Measurements
VA performed short-term measurements at the project site on Friday, August 7, 2015, circa 4 PM. The
existing daytime noise levels around the project site were measured at 50 dBA at the locations at the
rear of the site and measured at 59 dBA at the locations at the front of the site facing Highway 78.
Locations are shown in Figure 2 below.
Figure 2 -Measurement Locations
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Quarry Creek Development -Exterior Envelope Acoustical Design
August 24, 2015
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3.2 Computer Modeling
To predict exterior noise levels across the site VA utilized Bruel & Kjaer Predictor version 10.0; the
model was generally calibrated to the measurements using the traffic counts from CalTrans for
Highway 78 {136,000) which is the only noise source affecting the site. The noise contour map
generated is shown in Figure 3 below; the site plan has been overlaid. The calculated LDN at the front
of the site 65 LDN.
Figure 3: LON Noise Contours
4.0 INTERIOR NOISE CALCULATION
4.1 Exterior Construction
VA has assumed that the exterior wall will consist of stucco on single stud wall with batt insulation
filling the stud cavity, and a single layer of 5/8 inch type 'x' gypsum board on the inside. VA's
calculations include the exterior wall but indicate t hat t he interior noise levels are determined by the
acoustical performance of the glazing system.
4.2 Glazing Required to Meet Interior Noise Criteria
VA calculated the interior level within the residential unit s given the measured noise environment and
the exterior I construction described above. General glazing areas were used. Table 1 shows the
predicted interior LDN noise levels based on the windows and doors with STC rat ings as shown and
glazing construction as described in Appendix I.
Table 1 -Calculated Future Residential Interior Noise Levels (LON)
Location Exterior Window/door rating Indoor
LON LON
Highway 78 facade 65 STC 29 !>44
Remaining !> 62 No requirement, STC 29 recommended !>41 for project consistency
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August 24, 2015
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4.3 Mechanical Ventilation Requirement
Because the windows and doors must be kept closed to meet the noise requirements at the front of
the site, mechanical ventilation is required at these locations. The mechanical ventilation shall meet
all Code requirements.
5.0 CalGreen
As the noise levels do not exceed 65 dBA at any hour, there are no special glazing recommendations
for non-residential spaces.
6.0 CONCLUSIONS
The following is a summary of the acoustical items to satisfy the noise criteria of the Building Code and
General Plan of the City of Long Beach.
• Windows and glass doors with minimum STC ratings as shown in Tables 1 and minimum TL
values as outlined in Appendix I.
• Typical exterior wall construction.
• Mechanical ventilation systems for all units facing Highway 78.
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.
We trust this information is satisfactory. If you have any questions or comments regarding this report, please do
not hesitate to contact us.
Sincerely,
Veneklasen Associates, Inc.
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Cathleen Novak
Associate
www.veneklasen.com
~ Veneklasen Associates
Quarry Creek Development -Exterior Envelope Acoustical Design
August 24, 2015
Page 5 of 5
APPENDIX I -GLAZING REQUIREMENTS
In order to meet the predicted interior noise levels described in Section 4.0, the glazing shall meet the
following requirements:
Acoustical Glazing Requirements: Minimum Octave Band Transmission Loss and STC Rating
Minimum Transmission Loss Min.
STC Rating Nominal Thickness Octave Band Center Frequency (Hz) STC
125 I 250 I 500 I 1000 I 2000 I 4000 Rating
STC29 1" dual 19 I 11 I 25 I 31 I 34 I 30 29
The transmission loss values in the table above can likely be met with the following glazing assemblies:
1. STC 29: 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.
Acoustical test reports should be provided for review by the design team to ensure compliance with
glazing acoustical performance requirements. The tests shall be performed on the entire assembly,
including frame and seals.
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