Cabrillo National Monument: Acoustic monitoring report, 2021

Meyer, Erik

doi:10.36967/2303446

This study arose from the Cabrillo National Monument (CABR) Resource Stewardship Strategy (RSS), which identified the need for baseline acoustic surveys in the park. One of the RSS stewardship goals was to minimize anthropogenic sounds outside and inside park boundaries to enhance the visitor experience. A Technical Assistance Request (TAR) for natural sounds inventory was submitted to the Natural Sounds and Night Skies Division. Therefore, in May 2021, the NSNSD gathered acoustic data at two sites in CABR to provide park managers with information about the acoustic environment, sources of noise, and the existing ambient sound levels within the park. On average, noise was present from 95 to 99 percent of the time across the two sites. The most common sources of noise were aircraft, motor sounds, and a foghorn. The maximum percent time audible for any detailed noise source was the foghorn at site CABR001, audible for 95% of a 24-hr period over 10 days of listening. Motor sounds were most audible at site CABR002, audible for 68% of the time. Overall, existing ambient sound levels (LA50) at sites at CABR were 39.5 and 43.1 dB during the day and 34.7 and 42.5 dB at night during the sampling period (CABR001 and CABR002, respectively). Natural ambient sound levels (LAnat) were 30.2 and 38.0 dB during the day and 26.6 and 38.4 dB at night for CABR001 and CABR002 respectively, although these measurements were likely influenced by the high prevalence of noise. As a supplement, a geospatial sound model predicts existing and natural ambient sound levels at CABR are 46.0 (dBA) and 31.4 (dBA), respectively.

Cabrillo National Monument: Acoustic monitoring report, 2021

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