Underwater noise in Laguna San Ignacio has many sources including natural sounds from wind, rain, the tides, biological sounds from invertebrates, fish and whales, and human sounds from boats that operate in the lagoon. Overall, the “acoustic environment” in the lagoon can be very noisy depending on the contribution of all of the sources of noise. The LSIESP Acoustic investigation led by Dr. Aaron Thode of Scripps Institution of Oceanography (SIO) has recorded underwater noise in the lagoon since 2008. Dr. Thode and his researchers have begun to analyze these recordings and are providing sound “profiles” or graphs that show the frequencies of the noise, their intensity, and how these vary from year to year. This analysis is ongoing, but examples of the sound analyses are provided in their field report for 2013.
SIO graduate student Kerri Seger conducted a preliminary analysis of the data from the Punta Piedra recordings to investigate the overall noise budget across four different frequency bands. The bands were purposefully selected to approximately match various known sound sources. They include 5-25 Hz (related to tidal noise and fish sounds), 10-140 Hz (mainly dominated by gray whale calls), 200-1000 Hz (due to boat engines and some gray whale calls), and 1000-3125 Hz (caused by near-by boat engines, wind, and snapping shrimp). A comparative analysis was performed between this year’s noise budget and past years (2008-2012) at both the Punta Piedra location and at another location close to the Kuyima Ecoturismo campground on the southern shore of the lagoon’s interior.