PNNL

Abstract

Pseudosound caused by turbulent pressure fluctuations in fluid flow past a hydrophone transducer, often referred to as flow noise, can mask propagating sounds of interest. Flow shields can reduce the non-acoustic pressure fluctuations sensed by a hydrophone and mitigate this challenge, but few quantitative evaluations of flow shield performance exist. Here, we evaluate the performance of three hydrophone flow shields in a tidal channel: two types of nylon fabric and an oil-filled enclosure. All three flow shields reduce flow noise contamination, but the oil-filled enclosure performs best, reducing flow noise by 31 dB at 40 Hz and a current speed of 1.3 m/s.