Vertical array distributed acoustic sensing using looped and spiral geometries for waterborne acoustic signals up to...

Distributed Acoustic Sensing (DAS) has become a widely used passive acoustic monitoring method but faces challenges recording above a few hundred hertz. The goal of this study was to improve detection and signal-to-noise ratio (SNR) of higher-frequency signals, which could expand monitoring of fish and marine mammals. This study tested a cable with loops and a cable spiraled around a fiberglass tube deployed vertically from a vessel in Puget Sound, Washington, at a depth of approximately 100 m. The systems were tested with varying acquisition parameters, using impulsive signals from a bubble pulser and a 50 Hz to 1.5 kHz sequence from a Lubell VC2C transducer, with hydrophones as references. SNR was estimated in the time-frequency domain to account for unequally frequency-distributed noise. Both configurations improved SNR compared to straight cable sections and the looped configuration recorded up to the Nyquist frequency. Orientation and distance of the cable relative to the sources likely influenced signal detection, but constraints of this study prevented a direct evaluation of incident-angle-dependent sensitivity. The study shows the capability of vertical looped and spiral DAS systems to detect waterborne acoustic signals up to 3 kHz and highlights the importance of experimental design on data quality.