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Acoustics Audiovisual Telecommunications Security 130 Sutter Street F clot 5 Son Franc sco CA 94104 T 415 3970442 F 415 397 0454 ..wsv crosalter tom 536 St. John Street Residences Environmental Noise and Vibration Study 1 July 2016 Page 4 Measured train vibration levels exceeded the FTA general assessment criteria. It should be noted that vibration levels in this report were measured at- grade. The FTA document identifies that vibration will change as it enters the building. However, the effect of the building on vibration is dependent on the structural design. RECOMMENDATIONS Residential Interior Noise We calculated the window and exterior door STC7 ratings needed to meet the project criteria using the building and unit plans dated 16 May 2016 and the Site Plan dated 2 June 2016. The recommended STC ratings are for full window assemblies (glass and frame), rather than just the glass itself. Tested, sound -rated assemblies should be used. For reference, typical one -inch glazing assemblies (two 1/4 -inch thick panes with a 1/2 -inch airspace) achieve an STC rating of about 32. Where STC ratings above 33 are required, at least one pane will need to be laminated. To meet the indoor DNL 45 dB criterion, it will be necessary for some of the facades to be sound - rated. The window and exterior door STC ratings needed to meet the criterion are shown on Figure 2. For our calculations, we assumed the following: • Bedrooms will have carpet • All other rooms will have hard - surfaced flooring • Room sizes and locations are as shown on the unit plans • Window sizes and locations are as shown on unit plans and elevations Where windows need to be closed to achieve an indoor DNL of 45 dB, an alternative method of supplying fresh air (e.g., mechanical ventilation) should be considered. This applies to all residences. This issue should be discussed with the project mechanical engineer. Rail Vibration Redudng potential rail vibration in the building could Include the following approaches: stiffening the structure, or even trenching. We would be available to discuss this with your structural engineer and provide them with our measured data so they could assess what potentially could be done to reduce rail vibration from the trains to below 80 VdB. 7 STC (Sound Transmission Class) — A single- number rating defined in ASTM E90 that quantifies the airborne sound insulating performance of a partition under laboratory conditions. Increasing STC ratings correspond to improved airborne sound insulation. Charles M. Salter SSOCIAT { =, luC