Ex. G <br />13) Model did not calculate generator noise on homes to the east or any noise to the north. <br />14) Generator noise model did not include the excluded reflection effect of the addition building <br />wall. Calculation assumed noise source is out in the open. The reflection doubles sound power <br />projected to the east, south and west. <br />15) Octave analysis shown in the accompanying report reveals the noise model underestimates <br />generator noise impact by 10 dBA, primarily because the dBA noise level is controlled by noise <br />in the low frequency range, not the mid-range as SSA assumed. <br />16) Barrier effects are over estimated. Octave analysis reveals low frequency, not mid-range <br />noise defines dBA level. Noise barriers are less effective for low frequency noise than if the <br />noise was primarily mid-range frequency as assumed by SSA. <br />17) Octave analysis of generator exhaust/muffler, using data supplied for the particular model <br />based on generator exhaust pipe diameter reveals SSA underestimated noise by 3 dBA. <br />18) Wall and ground reflections are left out of generator exhaust noise model underestimating <br />exhaust noise by an additional 6 dBA. <br />19) Making these adjustments to the Generator + AC noise predicts neighborhood noise levels in <br />the range between 53 and 62 dBA. <br /> <br />20) The angled -on back scatters sound around the <br />SW corner of the addition, decreasing the -15 sound barrier effect and increasing the noise level <br />at the west property corner. <br />21) EC 6.750(b) is violated when generator runs unless a formal variance is granted. <br />Conclusions <br />SSA provided two noise reports. The first one contains their noise study and the second one <br />corrects a couple minor details in the first report of negligible consequence. <br /> <br />Code requires collocated equipment to be part of tower. Noise model does not include additional <br />impact due to collocated equipment being added to proposed site. Noise model was not based on <br />an octave analysis which resulted in the underestimation of generator noise impact levels. Noise <br />wall. And finally, there is no mention of additional potential mitigation measures being available <br />which can be implemented should the present design fail to comply with code. <br />Respectfully, <br />Arthur Noxon, PE <br />Acoustical Engineer <br />2 <br />