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Jerry Raney <br />31 March 2008 <br />Page 3 <br />Our single-event noise calculations are based on the measured train horn noise level of <br />82 dBA; some train horns may exceed this level. <br />For your reference, the following is a summary of typical wall constrnctions and their STC <br />rating: <br />• STC 42: 2 x 4 studs, batt insulation in the stud cavity, wood siding over exterior <br />plywood, one layer of gypsum board at the interior <br />• STC 50: Either 2 x 4 studs, Batt insulation in the stud cavity, wood siding over exterior <br />plywood, one layer of gypsum board with resilient channels at the interior or 2 x 4 studs <br />staggered on a 2 x 6 plate, batt insulation in the stud cavity, wood siding over exterior <br />plywood, one layer of gypsum board at the interior <br />Standard dual-pane constntction-grade windows typically achieve an STC rating of 28. It is <br />important to note that the STC ratings are for full window and door assemblies (glass-and- <br />frame) rather than just the glass itself. Tested sound-rated assemblies should be used. <br />Where sound-rated windows are needed, an alternate method of providing fresh air (e.g., <br />mechanical ventilation) must be provided. The project mechanical engineer should review <br />this issue. <br />Exterior Noise Levels <br />The measured DNL noise level is below 60 dBA, which is in compliance with the City's <br />exterior noise goal. No mitigation is required. <br />This concludes our environmental noise study for 4693 Augustine Street. If you have any <br />questions, please call. <br />Sincerely, <br />CHARLES M. SALTER ASSOCIATES, INC. <br />%~ ~~~-_ <br />Randy Waldeck, LEEDAr <br />Principal Consultant <br />RDW <br />2008_03_31 4693 Augustine St (08-0075) Env I.etter.doc <br />C h a r l e s M $ a I t 8 r Associates I h C 130 Sutter Street San Francisco California 94104 Tel: 415 39] 0442 Fax: 415 397 0454 <br />