Ex. F <br />There is no such thing as a GT-201-5100 Silencer. This number refers to a product line with 17 <br />different models, each of which has a different response curve. The models vary according to the <br />diameter of the exhaust pipe they are connected to. When reviewing literature on the 201-5100 product <br />but otherwise not specified as to which of the 17 models it applies to. <br />The only way to actually get a model specific attenuation curve is to contact engineering at the <br />manufacturer and they have the exact attenuation curve for each model. In general small diameter <br />exhaust pipe models have better attenuation curves than large exhaust pipe models. By matching the <br />exhaust pipe diameter to that of the generator,the silencer a specific attenuation curve is available. <br />Spec sheets from GT Exhaust give different attenuation estimates: One spec sheet for 201-5100 Series <br />sumption of 30 dBA does fit the range of data <br />available but claiming 35 dBA exceeds published data from GT on this product line. <br />There is no justification for raising the muffler from 30 to 35 dBA. A conservative and socially <br />responsible approach is to agree that the muffler at least produces 25 dBA and to use that figure. An <br />engineer will subtracting the muffler attenuation from the noise output of the engine, octave by octave <br />and assessing the resulting noise output curve, which was not done here. <br />3) Exhaust South <br />South table. That exhaust noise of 31 dBA <br />The last bullet comment addresses the receiving property <br />not 36 dBA should have been used as the noise impact level for the south property. These numbers <br />appear to be inconsistent with the information presented in the mentioned table. The muffler Noise <br />Control rating used is 35 dBA and the distance attenuation factor used is 36 dBA. The calculated dBA <br />impact for the south residential property was calculated to be 102 35 36 = 31 dBA, instead of 36 <br />dBA as claimed. Either way, the consequence on the overall calculation is inconsequential. <br />Conclusion <br />The SSA revision is a technical adjustment of tabular detail combined with an unwarranted increase in <br />promised performance from a muffler <br />anticipated performance. I have shown in a separate submittal how the SSA noise report significantly <br />underestimates the noise impact of the planned cell tower. Finally, the SSA report fails to present its list <br />of backup mitigation measures which are held in reserve and can be implemented should the actual <br />installation fail to meet its proposed compliance levels. <br />Respectfully Submitted <br />Arthur Noxon, PE <br />Acoustical Engineer <br />4 <br />