Ex. E <br />Generator Exhaust with Muffler <br /> <br />Octaves 63 125 250 500 1K 2K 4K 8K dBA <br />Generator exhaust @ 1m 74.1 88.1 89.7 92.2 97.5 95.0 94.9 90.0 102.1 <br />Mfg spec sheet, dBA <br /> 23 30 38 35 29 26 27 26 <br />Bruce at AIC <br />Exhaust, dBA @ 1m 51.1 58.1 51.7 57.2 68.5 69.0 67.9 64.0 74.0 <br /> <br />Difference, dBA 28.1 <br /> <br />For this generator the GT muffler is A201- <br />overestimated assumed muffler effect to be 30 dB,A when it actually is 28.1dBA. SSA over <br />estimation is 1.9 dB too high. <br />SSA also assumed that the exhaust rating was 102 dB,A @ 3 feet. However it is 102.1 dB,A at 1 <br />meter. This difference means that SSA has been underestimating the sound power out of the raw <br />exhaust pipe. The difference is 20 log 3.3/3 = 0.83 dB. <br />Add the difference between 201.1 and 201 = 0.1 dB and the total under estimation of the <br />loudness of the exhaust calculations by SSA is is 0.83 + 0.1 = 0.93 dBA. The total over- <br />estimation by SSA of the muffler is 1.9 dB + 0.93 dB = 2.83 = 3 dB overestimated benefit from <br />muffler. If there are no other adjustments, this means the according to SSA analysis, the West <br />receiving property muffler impact should not be 45 dBA as shown in SSA report but 48 dBA. <br /> property to the South, SSA 36 dBA has to be corrected to 39 dBA. <br />And <br /> <br />However, this +3 dB correction is not the only correction to be made to the SSA exhaust pipe <br />calculation. Exhaust <br />in front of a wall Q = +3 dB. Exhaust above the ground, Q = +3 dB. Total Exhaust Q is +6 dB. <br />SSA did not include Q factors in their Distance Factor calculation. <br />By combining the +6 dB Q adjustment because of directivity or megaphone effect to the exhaust <br />to the +3 dB over estimated attenuation effect of the muffler, we see that the generator exhaust is <br />actually 9 dB louder than the originally calculated level by SSA. <br />West <br />shown to be 9 dB underestimated. The actual prediction should be 45 + 9 = 54 dBA. To this <br />must be <br />in line with the face of the equipment room addition. This backscattering of sound should raise <br />59 dBA <br />the noise level at the property line by about +5 dBA, from 54 dBA to . <br />South <br />For the South property line the SSA prediction is 36 dBA but with the + 9 dB adjustment it <br />45 dBA <br />becomes . <br />13 <br />