Adam R. Maxwell

Small vessel contribution to underwater noise

Understanding the types of noise generated by a small boat is important for ensuring that marine ecosystems are protected from detrimental anthropogenic noise. Here we present the results of a field test conducted to examine the effects of engine RPM, number of engines and number of propeller blades on the broadband and narrowband noise produced by a small boat. The test boat was a 23-foot aluminum-hulled boat with dual 100 hp engines. The broadband noise and narrowband peak levels were observed using two hydrophones in different locations. The broadband noise levels were affected by both the number of engines and the RPM; the narrowband peaks showed a greater increase in amplitude with an increase in RPM than the broadband noise levels.

Observing ocean ecosystems with sonar

There is still much to learn about ocean ecosystems. Long-term, continuous observations of underwater environments can help improve our understanding. This is especially important as we continue to develop ocean energy resources. The Pacific Northwest National Laboratory (PNNL) and the University of Washington have developed a real-time processing system for sonar to detect and track animals, and to extract water column biomass statistics in order to facilitate continuous monitoring of an underwater environment. The Nekton Interaction Monitoring System (NIMS) is built to continuously process in real-time a stream of sonar data and archive tracking and biomass data, reducing the volume of stored data by orders of magnitude. The prototype system has been tested for real-time performance in the laboratory and in an operational environment on-board a research vessel and as part of a multi-instrument monitoring system. NIMS currently works with three types of sonar: a multi-beam sonar, a split-beam echo sounder and an acoustic camera.