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Home My WebLink AboutCT 2018-0004; THE SEAGLASS; EXTERIOR NOISE AND EXTERIOR ACOUSTICAL ANALYSIS; 2018-04-15"L.\ Veneklasen Associates v~ Consultants in Acoustics I Noise I Vibration I AV I IT April 15, 2018 Safdie Rabines Architects 925 Fort Stockton Drive JUN O 6·2018 CITY OF CARLSBAD PLANNING DIVISION San Diego, California 92103 Attention: Scott M. Maas, LEED AP I Principal The Seaglass Subject: Carlsbad, California Exterior Noise and Exterior Fa~ade Acoustical Analysis VA Project No. 4003-019 Dear Scott: Veneklasen Associates, Inc. (VA) has completed our review of the Seaglass residential condominium project located at 2646 State Street in Carlsbad, Californic!, This report predicts the exterior noise level at the site using measurements. Using this information, interior noise levels were calculated based on the exterior noise exposure and the construction types proposed. From this, the exterior fac;:ade design was determined. 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 Seaglass residential condominium 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 eight residential condominium units with individual garage spaces at the ground floor. The project is bounded by State Street to the west with the LOSSAN Rail Corridor beyond, existing residential uses to the north and east, and existing commercial uses to the south. 2.0 NOISE CRITERIA CNEL (Community Noise Equivalent Level) is the 24-hour equivalent (average) sound pressure level in which the evening (7 pm :a... io 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 Guidelines Manual 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 may be required. 1711 Sixteenth Street • Santa Monica California 90404 • tel: 310.450.1733 • fax: 310.396.3424 • www.veneklasen.com ½ Veneklasen Associates The Seaglass; Carlsbad, CA Exterior Noise and Exterior Fa~ade Acoustical Analysis VA Project No. 4003-019 April 15, 2018-Page 2 Although not a regulatory requirement, VA suggests that the maximum noise level from short- duration noise events during the night not exceed 55 dBA. VA's suggestion is based on sleep disturbance research and our experience with similar projects. 3.0 EXTERIOR NOISE ENVIRONMENT 3.1 Noise Measurements Train events from the LOSSAN Rail Corridor, along with minor traffic on State Street, were the prima ry sources of noise affecting the site. VA visited the site on Wednesday, April 4, 2018 and placed a sound level meter along State Street to capture the hourly sound levels on the site for a 24-hour period. VA also made short-term noise measurements. VA measured several train events from the LOSSAN rail corridor which occurred during the nighttime hours between 10 pm and 7 am. Table 1 and Figure 1 show the location and summary of the noise measurements. Table 1-Measured Sound Levels Measured Average Location Level, Measured Nighttime Event CNEL Maximum, Leq dBA Lmax dBA Ll -65 90 Sl 51 -- S2 44 -- S3 47 -- Site Boundary ~ Short-term Measurement ~ Long-term Measurement www.veneklasen.com "\r\-Veneklasen Associates 3.2 Overall Exterior Exposure The Seaglass; Carlsbad, CA Exterior Noise and Exterior Fa~ade Acoustical Analysis VA Project No. 4003-019 April 15, 2018-Page 3 Based on the measurements, VA calculated the noise level at different locations across the project site. To simplify the presentation of the exterior noise levels, VA has separated the site into locations based on the sound exposure and required mitigation. The predicted sound levels at each zone, shown in Figure 2, are listed in Table 2 below. Table 2 -Exterior Noise Levels Location Floor Exterior Noise Train Max, Level, CNEL dBA Zone A All 65 90 Zone B All 60-65 88 Zone C All 60-65 88 Figure 2 -Noise Zones 4.0 INTERIOR NOISE CALCULATION 4.1 Exterior Facade Construction The exterior wall will be a three-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. Calculations were based on the plans dated February 2, 2018. Table 3 shows the predicted interior CNEL noise levels based on the windows and doors with STC ratings as shown and glazing construction as described in Appendix I. www.veneklasen.com "\f\-Veneklasen Associates The Seaglass; Carlsbad, CA Exterior Noise and Exterior Fai;ade Acoustical Analysis VA Project No. 4003-019 April 15, 2018-Page 4 Table 3-Calculated Interior CNEL Noise Levels Exterior Noise Window/Door Interior Noise Interior Location Floor Maximum, Level, CNEL Rating Level, CNEL dBA All Zones All 60-65 STC30 <45 s 69* * The glazing indicated in Table 3 above is provided strictly to meet the requirements set forth in California Building Code (CBC} Title 24 for interior CNEL. 4.3 Mechanical Ventilation -Residential Because the windows and doors must be kept closed to meet the noise requirements, mechanical or other means of ventilation may be required for all units. The ventilation system shall not compromise t he sound insulation capability of the exterior facade assembly. 5.0 SUMMARY The following summarizes the acoustical items required to satisfy the noise criteria as described in this report. Residential • 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 ratings as shown in Table 3 with STC ratings an octave band Transmission Loss specified in Appendix I (Table 4) are required . • Residential mechan ical ventilation, or other means of natural ventilation, may be required 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 regard ing this report, please do not hesitate to contact us. Sincerely, Veneklasen Associates, Inc. er Joh n Loverde, FASA Principal www.veneklasen.com ½ Veneklasen Associates APPENDIX I -GLAZING REQUIREMENTS The Seaglass; Carlsbad, CA Exterior Noise and Exterior Fac;ade Acoustical Analysis VA Project No. 4003-019 April 15, 2018-Page 5 In order to meet the predicted interior noise levels described in Section 4.0, the glazing shall meet the following requirements: Table 4 -Acoustical Glazing Requirements: Minimum Octave Band Transmission Loss and STC Rating Minimum Transmission Loss Min. Nominal Thickness Octave Band Center Frequency (Hz) STC 125 I 250 I 500 I 1000 I 2000 I 4000 Rating 1" dual 21 I 18 I 27 I 34 I 37 I 32 30 The transmission loss values in the table above can likely be met with the following glazing assemblies: 1. STC 30: 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 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 current member of the NVLAP program for accreditation and shall be pre-approved by Veneklasen Associates, Inc. Tests are required to be completed in North America. 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). VA requires invitation to witness acoustical testing completed to demonstrate compliance with the requirements of this report and reserves the right to exclude test reports from laboratories that are not pre-approved by Veneklasen Associates, Inc. for the specific test standard. The tests shall be performed on the entire assembly, including frame and seals and hardware, if applicable to be used for the project. 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. www.veneklasen.com