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performance zone. The location of Building A in the CAC cluster blocks the increased sound levels from the southwest. Performance sound impacts will be minimized given that this location is equidistant from surrounding neighborhoods, and the stage and audience are oriented towards open space and the freeway. There is the likelihood that performance sound would carry to the Pleasanton Ridge to the west. Conclusion Freeway traffic generates a background noise that is directly experienced up close and indirectly experienced as ambient sound from a distance. These sound waves can be controlled more easily when closer to the freeway. A solid barrier that is at the back of and higher than the audience will absorb the sound waves, protecting the audience within the sound shadow. The closer the audience is to the freeway noise, the smaller/shorter the noise barrier needs to be in order to block direct sound. Any sound waves that pass above the audience will not be heard. The architecture surrounding the amphitheatre can be designed to deflect the freeway sound waves up into the air. In addition to attenuation at the CAC perimeter, the City could also consider working with CalTrans to install a K-wall barrier along the eastern edge of the freeway from the overpass at the UPRR tracks to some point northern, near the northbound off ramp at Bernal Avenue. Performance sound within the outdoor amphitheatre will leak out by reflecting off of walls and sloping ground. Speakers can be directed at the audience to minimize this effect. Nonetheless, the sound waves that are not absorbed by audience and plant material will be reflected into the air and be heard from some distance away. The analyses of site locations, given the dynamics of off-site and on-site generated sound would clearly favor a southern location for the CAC and amphitheatre. This location makes it easier to mask freeway noise while placing the performance sound source at a location that is the farthest from surrounding neighborhoods. It is very possible that a location toward 1-680 would actually be more advantageous with respect to site sound issues. Siting venues at the opposite end, in close proximity to Bernal Avenue, is likely to project unwanted performance sounds into neighboring areas. This is very common in urban park settings where amphitheatres exist. Sound from events in an amphitheatre closer to the highway will have less impact because of greater open space, less housing density off axis, and acoustical "masking" by 1-680 traffic. The greatest concern would be residences on the Pleasanton Ridge, but as long as speakers are appropriately aimed and oriented, this should not be an issue. page 4 I M.D. FOTHERINGHAM, LandseapeArchirecuInr. 323Gea~ S~ee~ Suite407 San Franc~co, CA 94102 415-434-8292