A Study of the Spectral and Directional Properties of Ambient Noise in Puget Sound PDF Download

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Category : Marine mammals
Languages : en
Pages : 77

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Book Description
"This brief pilot study successfully demonstrates the ability to set a permanent noise level to assess the influence of transient signals on the ambient noise environment. This is of particular importance to assessing the health of endangered species, like the SRKW, and to help develop better means of protecting them. Transient signals causing temporary elevated levels above the permanent noise level are confirmed by a directional analysis of the ambient noise. The calculated permanent noise levels have a consistent angular distribution in the vertical plane. Departures from the permanent noise levels correspond to a change in the angular distribution of noise, which in general corresponds to angular distribution developing a significant component of horizontal noise. The mechanisms causing these increased levels are most likely anthropogenic sources. The major anthropogenic sources in Puget Sound are large ships and local boat traffic. Airplane flyovers can also contribute but an exact quantification of this source to the overall noise budget is not possible with this limited data set. An assessment of the data shows that these all play a role in the ambient noise environment, at times elevating the noise levels above the permanent noise levels. Further study of a longer duration will allow for a development of the frequency of these events and their temporal dependence, statistics that can be used for an impact assessment of anthropogenic noise sources From the standpoint of an engineering experience, the importance of good system design is essential to capture the desired experimental data. The DPAL acts as an excellent high frequency recorder, but is susceptible to error from backscattered pressure, when the phase information between the two channels is desired. With a clear goal in mind, the SUNFISH recording system, created to measure sound on both sides of the sea surface, successfully captured noise data confirming the theory governing the transmission of sound across the air-water interface. Drawing lessons from the data analysis of the systems deployed in this study, future system development need be more cognizant of the influence of system geometry on acoustic measurements."--Conclusions.