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Forward Landfill LFG Acoustical Analysis Page 8 May 18, 2011 5 NOISE CONTROL REQUIREMENTS The computed off-site noise levels shown in Table 3 are based on the noise emissions levels provided by equipment manufacturers and a 15 dB indoor to outdoor attenuation factor for the metal building surrounding the generator engines. To achieve this degree of sound insulation for noise sources producing significant low frequency noise, ventilation openings should employ acoustic treatment such as 12-inch thick lined acoustic louvers and the wall and ceiling surfaces should be lined with perforated metal- faced fiberglass or mineral fiber sound absorbing treatment. Nominally, the surface density of the building skin should be at least one pound per square foot. Note in Figure 5 that the louver banks are incorporated on the south side of the building, configured to reduce flow velocity for prevention of rain ingestion. In view of the great distance to noise sensitive receptors in the southerly direction, it would be possible to make the noise reduction louvers optional at this installation. They could easily be added at a future date if additional noise suppression is desired. 6 CONCLUSION Based on manufacturers' noise emission levels for proposed equipment, noise levels below the San Joaquin County 50 dB daytime and 45 dB nighttime limit and further reduction to match probable nighttime ambient noise levels will be achieved through use of acoustic enclosures and high efficiency engine exhaust silencers.