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1 <br />STEP 9: DETERMINE ADJUSTED WINDOW STC <br />The following corrections should be made to the basic window STC ratings <br />determined from Figures 1 through 6. <br />When there are more than two exterior walls in a room +3 STC <br />Rooms without carpeting or soft furniture +2 STC <br />Resilient mounting of interior gypsum wall -1 STC <br />If door rating is less than 26 STC +1 STC <br />• <br />If patio door rating is 26 STC and area is over 5 percent +2 STC <br />STEP 10: SELECT WINDOWS TO MEET STC REQUIREMENT <br />Compare the STC ratings of the proposed windows as determined in Step 6 and <br />compare these with the required adjusted value determined in Step 9. If the <br />proposed STC value is insufficient to meet the requirement, then one or a <br />combination of the following alternatives should be considered: <br />1. Select a window (Step 6) with the required STC value. <br />2. Reduce window area. <br />3. Use walls, roof -ceiling assemblies or patio doors with higher STC values. <br />STEP 11: PREPARE ACOUSTICAL REPORT <br />If the design can be shown to meet the noise level reduction required, the <br />completed acoustical report should then be submitted to the local building <br />inspector. An example is shown in Table 3. <br />STEP 12: MEASURE BUILDING PERFORMANCE <br />Acoustic testing may be required under the city ordinance if the plans are <br />changed following the acoustical review and no subsequent substantiation of the <br />building performance is provided to the building inspector. <br />Should testing of the finished structure be necessary, the ASTM (American <br />Society for Testing Materials) E-336 standard for measuring exterior -interior <br />noise reduction should be followed. This test is described in the 1987 Annual <br />Book of ASTM Standards (see references). <br />Use of this Guide does not guarantee that a specific noise level reduction can <br />be met. <br />21 <br />