Abstract:
The U.S. Marine Corps scheduled demonstration helicopter flybys for 7 and 8 December 1995 over the City of Del Mar, CA, and Torrey Pines State Reserve to the south, and other cities also. Residents were invited to comment on noise; this paper is based on my measurements and comments. City of Del Mar Regulation 9.20.03 provides that the 1-h average sound level beyond the property on which noise is produced shall not exceed 50 dB, from 7 a.m. to 10 p.m. Noise at Torrey Pines was monitored continuously for 10 days. During the scheduled times on 7 and 8 December there were fourteen 1-h average sound levels greater than 55 dB; during 7 of those hours, the 1-h average sound level was greater than 60 dB. The Torrey Pines monitoring site was about 2500 ft from the Seawolf track south of Del Mar, on which some of the helicopters flew at a scheduled altitude of 1000 ft outbound, 500 ft inbound. To provide a common basis for comparison, measurements were interpreted to yield the A-weighted sound exposure level (SEL) at a sidewise distance of 1000 ft from a helicopter. For the CH46E helicopter the typical SEL was 90 dB; for the CH53E helicopter, it was 97 dB.