06/25/2003 Env Bd Packet - Laserfiche WebLink

Home Search

• .MAY 24 '96 14:44 FROM nAUID BRASLAU ASSOC PAGE.005 • Noise level t homes from_, oeltors facing west (without bubble) Based upon previous studies of crowd noise, the noise level from spectators is estimated at a maximum of 72 dBA. This will last only a short time since maximum shouting effort can only be supported for a short duration. Moreover, this level of noise occurs only periodically during sporting events. Crowd noise occurs more suddenly than aircraft but lasts a shorter time. A typical level of an overflying jet aircraft was observed at 72 dBA in the area, but that level lasted for 20 to 40 seconds. • Noise level at homes from lightpole- mounted speakers directed towards the east With speakers mounted on light poles on the west side of the playing field, but pointed towards the east to cover the bleachers, the estimated level at the homes is 60 dBA without any additional shielding of the speakers. This assumes directional .speakers that focus the energy towards the east and do not spill or waste sound energy behind the speakers.. With structural shielding of the speaker, a level of 45 dBA is expected at the residential • . neighborhood. Since speech carries information content and is different from background noise, it may be intelligible although careful speaker design should be able to minimize its intrusiveness. • Eloise reflections from the bubble towards homes Trucks or trains traveling between the homes and bubble generate noise that could also be reflected from a structure on the Holy Angels property. Because of its construction, the fabric bubble will reflect primarily higher frequencies that decay faster in the atmosphere. Also, because the bubble is curved (see copy of overhead in APPENDIX A) , reflected sound is likely to be reflected upwards and over the adjacent neighborhood. A permanent structure with vertical walls could generate reflected noise and hence possibly increase noise levels from intervening traffic. This also suggests, however, that any low frequency noise. generated within the bubble is likely to be Less attenuated by the bubble fabric. Academy of the Holy Angels - Noise Assessment I RECEIVED JUN 0 9 2003 CITY OF LINO LAKES Page 3