Growing human population in coastal areas within the last century has intensified the level of underwater sound pollution globally and consequently its impact on marine habitats. The increased complexity in the ambient underwater soundscape of the urbanized shoreline is due to the convoluted use of nearshore and coastal waters for marine related activities such as recreational and commercial boating, shoreline roads, and industrial and residential development. These uses impose stress on the ecological quality of nearshore habitats for Pacific Northwest fish during transit through urbanized waters. This study examined the characteristics of ambient sound sourced from traffic on the I-5 Bridge in Seattle, Washington near Portage Bay on February 12th, 2015. The soundscape was investigated through passive acoustic measurements of ambient underwater sound at varying distances from the bridge using two built hydrophones utilizing piezo elements and three professional grade hydrophones, in effort to prototype the built hydrophones and ensure quality data collection. The propagation and attenuation of sound from the I-5 Bridge characterized the potential for this point source of sound pollution to impact fish during transit. The variation in the acoustic spectrum at multiple distances from the bridge identified the spatial extent of preferential attenuation of frequencies and intensity of sound as a contributor to noise pollution. Fish utilize the canals connecting the Puget Sound to Lake Union and Lake Washington, where bridge noise pollution could be affecting their behavior during migration.

In collaboration with Booz Allen Hamilton, our E E 497/498 Entrepreneurial Design Capstone project addresses the challenge of taking precisely georeferenced photographs of the underwater domain. These photographs will be mapped onto existing bathymetric datasets (from sources like NASA and NOAA) to provide visual textures of static and dynamic underwater points of interest. Our team’s role is the design and implementation of the imaging system hardware, which will complement visualization software under development at Booz Allen Hamilton’s Seattle office. Our design extends the OpenROV 2.8 platform, a small open-source, tethered, remotely-operated vehicle (ROV), with emphasis on developing a successful prototype using commercial off-the-shelf (COTS) parts at minimal cost. In total, our team has implemented (1) the extension of OpenROV into an underwater imaging platform, carrying a payload enabling hemispherical imaging below the ROV; (2) the design of a tethered surface buoy system, with access to Differential GPS data to act as a reference for geolocating the ROV; (3) the design of an ROV-mounted acoustic transmitter and buoy-mounted acoustic receiver array to determine underwater distance between the ROV and each array element; (4) the design of an efficient trilateration algorithm using nonlinear and linear least-squares optimization to accurately position the ROV relative to the buoy based on (3). Our research has significant implications for improving access to the underwater domain, including low-cost maritime sensing and deployment applications and military training and simulation applications.

The inland waters of the Puget Sound, Washington, USA, and Georgia Basin, British Columba, Canada, is a complex system of high energy river inputs to lower energy large basins with direct connection to the open ocean through the Straits of Juan de Fuca. High energy systems acting as transport mechanisms for coarse sediment interact with low energy regions with transport deposition of finer sediments to create the vertical stratigraphy of the seafloor. In regions of high energy the seafloor expression is dominated by a rougher seafloor with more geomorphic features of coarser material, while low energy regions are expressed in a seafloor of uniform lamination. This research investigates the link between the surface expression of seafloor roughness and the underlying vertical structure of sediment deposition. Using a high resolution bathymetric surface derived from multibeam sonar synchronized with low frequency sub-bottom acoustic profiles, the depth of acoustic penetration is correlated with a focal calculation of seafloor roughness. Areas of lower acoustic impedance have a larger range in penetration, with lower ranges of penetration persisting in areas of high acoustic impedance. High acoustic impedance is indicative of harder sediments, such as sand, and low acoustic impedance indicates softer sediments, such as mud. The research is a comparative study between a high energy system adjacent to the mouth of the Elwha River and the low energy protected region of South Possession Sound. The research illustrates the strong link between seafloor geomorphology and the terrestrial sources of sediment input and mitigation of sediment transport energy.