03-31-11 Volpe Report: Baseline Ambient Sound Levels in Point Reyes National Seashore, March 2011, Final Report, United States Department of Transportation.
From the Report Documentation Page
“The …FAA, … is developing Air Tour Management Plans (ATMP) for all national parks with commercial air tours, …. An important area of technical support is the determination of representative baseline ambient sound levels for the study parks. During the summer (July – August 2009) and winter (January – February 2010), the Volpe Center conducted baseline ambient sound level measurements in Point Reyes National Seashore. Approximately one month of acoustical and meteorological data were measured at four sites throughout the park. This document summarizes the results of the noise measurement study.”
From Page 67
“Site PORE004 was located to near the Drakes Estero and Estero Trail in an exposed area with
nearby grasses and brush and a short distance from a bluff overlooking the Estero. ….
The overall median daytime sound level during the summer season was 33.8 dBA and humanrelated
sounds were audible during 17% of the daytime hours. The overall median daytime sound level during the winter season was 35.8 dBA … and human-related sounds were audible during 20% of the daytime hours. The daily sound level graphs demonstrate the influence of wind speed on the sound levels at this site. There was a small increase in audible aircraft overflights during the winter. Rain was much more prevalent in the winter season. There was also a noticeable lack of insect noise during the winter compared
to summer. Birds were audible for most of the daytime during both seasons.”
(emphasis added is mine)
For the complete report, click on the link below: