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Home My WebLink AboutCDP 2020-0007; TERRA BELLA DEVELOPMENT; ACOUSTICAL REPORT; 2020-06-18Steve Rogers Acoustics June 18, 2020 Jack Bian jack.l.bian@gmail.com Subject: Dear Jack: 6479 Surfside Lane, Carlsbad, CA Acoustical Report We report here the findings of an acoustical study of the 6479 Surfside Lane project in Carlsbad, CA 92011. Specifically, this report addresses Plan-Check Comment 11 for the project, which requires a noise analysis because of proximity of the project site to Carlsbad Boulevard. BACKGROUND • The project is a new single-family home located on the east side of Carlsbad Boulevard, between the intersections with Palomar Airport Road and Poinsettia Lane. The proposed structure will be two-stories of living space over a basement. • Our work has been based on Architectural floorplan drawings A2-200, 201, 202, 203 and elevation drawing A301; we understand that these were part of a package dated May 15, 2020. BUILDING ELEMENTS & ACOUSTICAL PERFORMANCE • The proposals for the exterior envelope include curtain wall at the west fac;ade, overlooking Carlsbad Boulevard. At the north, south and east facades, the drawings show smaller windows and doors punched into wood-framed solid wall elements. • Our understanding of the makeup of the exterior envelope is summarized in the Appendix of this report, which also provides the Sound Transmission Class (STC) ratings used in our analysis. Sound insulation performance for each element has been calculated using INSUL prediction software (see attached INSUL output sheets). • We understand that the home will be fully air-conditioned, so that it will not be necessary to open windows or doors for ventilation. Our calculations of traffic noise intrusion to the occupied space therefore assume that all windows and doors are closed . EXTERIOR NOISE LEVELS AT THE PROJECT SITE • At the time we were retained by the project developer, safer-at-home orders were in effect throughout California which greatly reduced the volume of traffic on the state's surface streets and freeways. It was not therefore possible to accurately determine the level of noise produced by Carlsbad Boulevard by direct measurement. • As an alternative, our study has been based on the noise contours provided in the City of Carlsbad General Plan . To be conservative, we have used the future (2035) noise contours shown in Figure 5-3 of the General Plan, which are slightly elevated compared to present day conditions. • Figure 1 in this report shows a portion of the 2035 noise map from the General Plan, including the location of the project site. 2355 Westwood Boulevard, Suite 411 Los Angeles, CA 90064 Tel: 310.234.0939 rogersocoustics.com '. . .. 6479 Surfside Lane, Carlsbad, CA Acoustical Report Figure 1: Excerpt from the City of Carlsbad General Plan noise contour map 2035 Noise Contours 1111 70 + CNEL 1111 65 -70 CNEL 60 -65 CNEL Project Site June 18, 2020 Page 2 of 4 • The General Plan shows the 65 Community Noise Equivalent Level (CNEL) contour at approximately 220-feet from the centerline of Carlsbad Bou levard, whereas the west fa~ade of the new home at 6479 Surfside Lane will be approximately 110-feet from the centerline of Carlsbad Boulevard. Since noise from a busy surface street is reduced by 3 dBA for each doubling of distance, we estimate that the west fa~ade of t he project will be exposed to a traffic noise level of 68 CNEL. • To estimate the likely frequency content of the traffic noise, we have referred to noise monitoring results from previous SRA projects located close to busy surface streets, which has led us to the predicted noise spectrum shown in Figure 2. Figure 2: Predicted traffic noise levels incident on the west fa~ade of the project 90 ct) "O C 80 a, Exterior > 70 QI _J CNEL = 68 ~ ::, 60 "' "' QI 0. "O 50 C ::, 0 40 V'l .... ::, 0 30 .c <;t N 20 "O QI .., .c Ill) 10 "ai ~ 0 63 125 250 500 lk 2k 4k 8k Octave Band Center Frequency in Hz .. 6479 Surfside Lane, Carlsbad, CA Acoustical Report June 18, 2020 Page 3 of 4 • The presence of the future structure on the project site will provide some shielding of traffic noise at the north, south and -especially -east facades. Our calculations have assumed that noise levels incident on the north and south facades will be 3 dB lower and those incident on the east fac;ade 10 dB lower than those at the west fac;ade. COMPLIANCE WITH PLAN-CHECK COMMENT 11 • Plan Check Comment 11 requires that noise intrusion to the occupied areas within the home be attenuated to 45 CNEL or less, consistent with the sound insulation requirements of the California Building Code. • To check for compliance with this requirement, we have calculated levels of noise intrusion to the various occupied spaces within the future home, based on the predicted exterior traffic noise levels incident on each fac;ade and the sound insulating properties of the exterior envelope of the building (as summarized in the Appendix to this report). Results are summarized in Table 1. Table 1: Predicted interior noise level in the occupied rooms due to intrusion of traffic noise from Carlsbad Boulevard SPACE Interior CNEL BASEMENT Entertainment Room 41.3 1st FLOOR Bedroom (typical of three) 40.4 Bathroom (typical north and south) 36.0 Study 34.1 Bar Room/Reading 35.8 2nd FLOOR Master Bedroom 41.8 Living/Dining/Kitchen 42.4 Master Closet 26.2 Master Bathroom 36.7 Powder Room 36.0 • As Table 1 shows, current proposals for the exterior envelope of the building (as summarized in the Appendix of this report) are consistent with the 45 CNEL interior noise limit prescribed by plan-check Comment 11 (and State Code); therefore, no changes or enhancements to the current design of the exterior envelope are required. Yours sincerely, Steve Rogers Acoustics, LLC d:\projects\xu\6479 surfside lane\report 1 6479 Surfside Lane, Carlsbad, CA Acoustical Report - APPENDIX -SUMMARY OF BUILDING ELEMENTS & ACOUSTICAL DATA Element Description/Construction* 3/4" cement plaster over 1/2" plywood sheathing over Solid Wall Elements 2x6 wood studs with batt insulation, 5/8" gypsum board lining. Roof Roofing membrane over 3/4" plywood over 2x10 joists with batt insulation, 5/8" thick gypsum board lining. FIXED ELEMENTS: 1-1/4" thick insulated glass assembly comprised of 1/4" glass -3/4" airspace -1/4" glass in aluminum frame. Curtain Wall OPERABLE ELEMENTS: 1-1/4" thick sliding doors comprised of 1/4" glass - 3/4" airspace -1/4" glass in aluminum frame. Punched Windows 7 /8" insulated glass assembly comprised of 1/4" glass - 3/8" airspace -1/4" glass in aluminum frame. Entry Door 1-3/4" thick solid-core wood. at East Fa~ade * Determined using INSUL sound insulation prediction software June 18, 2020 Page 4 of 4 Predicted Sound Transmission Class (STC)* 49 36 37 35** 34 30** ** High-frequency TL values reduced to take account of noise leakage at operable seals