Many marine species, including mammals, fish, and invertebrates, use sound or acoustic signals in the ocean for a variety of life functions, such as communication, foraging, navigation, and reproduction. Underwater noise is a stressor of concern for regulators who permit the deployment of marine energy devices. Sound emissions from these devices may increase background noise levels, which can mask important sounds for aquatic life, causing stress or changes in their behavior. To better understand potential sound disturbances resulting from marine energy, the Triton team studied methods to reduce unwanted flow noise contamination of acoustic recordings.  

Flow noise is pseudo-sound (non-acoustic pressure fluctuations) caused by turbulence in the flow of water past an acoustic sensor, like the crackling sound you hear when wind blows over a microphone. The Triton team performed research that addressed how to reduce the flow noise caused by water flowing by a hydrophone, which can severely limit the utility of underwater sound measurements. Through this project, Triton tested various flow shields designed to reduce the effects of flow noise. Flow shield tests took place in the tidal channel at the entrance to Sequim Bay, adjacent to Pacific Northwest National Laboratory (PNNL)-Sequim. The team deployed hydrophones with and without flow shields in an area of the channel where tidal currents exceed 1.5 m/s. The results of this work quantified the effectiveness of three types of flow shields that can be used to improve underwater noise characterization at high-energy marine energy sites.   

The project team published a paper titled “Performance of Three Hydrophone Flow Shields in a Tidal Channel.”  The paper presents results from a study that evaluated the performance of three hydrophone flow shields in the Sequim Bay tidal channel at PNNL-Sequim. Due to the flow shields’ ability to effectively reduce flow noise, these monitoring tools were successfully deployed during underwater noise monitoring in Igiugig, Alaska, for the PNNL Environmental Monitoring Campaign. Read the paper here!   

Additionally, the successful technology and development effort led to support from the DOE Technology commercialization fund to investigate commercialization with Triton’s industry partner, XFlow.