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Chris Bassett

Senior Mechanical Engineer

Email

cbassett@uw.edu

Phone

206-543-1263

Research Interests

Passive noise studies, acoustic scattering, sea ice, marine renewable energy, fisheries acoustics, anthropogenic noise

Biosketch

Chris applies passive and active acoustic techniques to a variety of underwater applications. Some of his previous and ongoing studies include fisheries acoustics; high-frequency scattering from sea ice, crude oil, and physical oceanographic processes; measurements of anthropogenic noise; and ambient noise studies.

Department Affiliation

Ocean Engineering

Education

B.S. Mechanical Engineering, University of Minnesota, 2007

M.S. Mechanical Engineering, University of Washington, 2010

Ph.D. Mechanical Engineering, University of Washington, 2013

Publications

2000-present and while at APL-UW

Acoustic characterization of sensors used for marine environmental monitoring

Cotter, E., P. Murphy, C. Bassett, B. Williamson, and B. Polagye, "Acoustic characterization of sensors used for marine environmental monitoring," Mar. Pollut. Bull., 144, 205-215, doi:10.1016/j.marpolbul.2019.04.079, 2019.

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1 Jul 2019

Active acoustic sensors are widely used in oceanographic and environmental studies. Although many have nominal operating frequencies above the range of marine mammal hearing, they can produce out-of-band sound that may be audible to marine mammals. Acoustic emissions from four active acoustic transducers were characterized and compared to marine mammal hearing thresholds. All four transducers had nominal operating frequencies above the reported upper limit of marine mammal hearing, but produced measurable sound below 160 kHz. A spatial map of the acoustic emissions of each sonar is used to evaluate potential effects on marine mammal hearing when the transducer is continuously operated from a stationary platform. Based on the cumulative sound exposure level metric, the acoustic emissions from the transducers are unlikely to cause temporary threshold shifts in marine mammals, but could affect animal behavior. The extent of audibility is estimated to be, at most, on the order of 100 m.

Flow-noise and turbulence in two tidal channels

Bassett, C., J. Thomson, P. H. Dahl, and B. Polagye, "Flow-noise and turbulence in two tidal channels," J. Acoust. Soc. Am., 135(4), 1764-1774, doi:10.1121/1.4867360, 2014.

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13 May 2014

Flow-noise resulting from oceanic turbulence and interactions with pressure-sensitive transducers can interfere with ambient noise measurements. This noise source is particularly important in low-frequency measurements (f < 100 Hz) and in highly turbulent environments such as tidal channels. This work presents measurements made in the Chacao Channel, Chile, and in Admiralty Inlet, Puget Sound, WA. In both environments, peak currents exceed 3 m/s and pressure spectral densities attributed to flow-noise are observed at frequencies up to 500 Hz. At 20 Hz, flow-noise exceeds mean slack noise levels by more than 50 dB. Two semi-empirical flow-noise models are developed and applied to predict flow-noise at frequencies from 20 to 500 Hz using measurements of current velocity and turbulence. The first model directly applies mean velocity and turbulence spectra while the second model relies on scaling arguments that relate turbulent dissipation to the mean velocity. Both models, based on prior formulations for infrasonic (f < 20 Hz) flow-noise, agree well with observations in Chacao Channel. In Admiralty Inlet, good agreement is shown only with the model that applies mean velocity and turbulence spectra, as the measured turbulence violates the scaling assumption in the second model.

Sediment-generated noise and bed stress in a tidal channel

Bassett, C., J. Thomson, and B. Polagye, "Sediment-generated noise and bed stress in a tidal channel," J. Geophys. Res., 118, 2249-2265, doi:10.1002/jgrc.20169, 2013.

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30 Apr 2013

Tidally driven currents and bed stresses can result in noise generated by moving sediments. At a site in Admiralty Inlet, Puget Sound, Washington State (USA), peak bed stresses exceed 20 Pa. Significant increases in noise levels are attributed to mobilized sediments at frequencies from 4–30 kHz with more modest increases noted from 1–4 kHz. Sediment-generated noise during strong currents masks background noise from other sources, including vessel traffic. Inversions of the acoustic spectra for equivalent grain sizes are consistent with qualitative data of the seabed composition. Bed stress calculations using log layer, Reynolds stress, and inertial dissipation techniques generally agree well and are used to estimate the shear stresses at which noise levels increase for different grain sizes. Regressions of the acoustic intensity versus near-bed hydrodynamic power demonstrate that noise levels are highly predictable above a critical threshold despite the scatter introduced by the localized nature of mobilization events.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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