Community noise at Del Mar, California, during two four‐day helicopter noise studies Free

Monday, 30 August 1999, was the first day of a four‐day Marine Corps demonstration of noise of helicopters flying north and south along the coast at Del Mar, California. The second four‐day demonstration was 26–29 October 1999. A Computer Engineering Limited automatic noise monitor operated continuously at 421 Ocean View Ave. or at 12839 Via Grimaldi. Helicopters flew 0.5‐ to 5‐mile intervals offshore, at altitudes 500 or 2000 feet above sea level. On 2 September 1999, at 421 Ocean View Ave., from midnight to 0800, the one‐hour average sound level was less than 41 dB. From 0800 until 0951, helicopter sound levels exceeded an 80‐dB threshold 15 times. During the hour ending at 1000, helicopter one‐hour average sound level was 72 dB. The maximum fast A‐weighted sound level MXFA was 94 dB. The A‐weighted sound exposure level ASEL was 103 dB. The 421 Ocean View site is 300 feet east of the shoreline and about 200 feet above sea level. Thus when a helicopter flies 0.5 miles offshore and altitude 500 feet above sea level, it is only 300 feet above and 3500 feet distant from the monitor at 421 Ocean View Ave.