Abstract
NoiseSpotter is a passive acoustic monitoring system that characterizes, classifies, and geo-locates anthropogenic and natural sounds in near real time. It was developed with the primary goal of supporting the evaluation of potential acoustic effects of offshore renewable energy projects. The system consists of a compact array of three acoustic vector sensors, which measures acoustic pressure and the three-dimensional particle velocity vector associated with the propagation of an acoustic wave, thereby inherently providing bearing information to an underwater source of sound. By utilizing an array of three vector sensors, the application of beamforming techniques can provide sound source localization, allowing for characterization of the acoustic signature of specific underwater acoustic sources. Here, performance characteristics of the system are presented, using data from controlled acoustic transmissions in a quiet environment and ambient noise measurements in an energetic tidal channel in the presence of non-acoustic flow noise. Data quality is demonstrated by the ability to reduce non-acoustic flow noise contamination, while system utility is shown by the ability to characterize and localize sources of sound in the underwater environment.
Highlights
The market acceleration and adoption of marine renewable energy (MRE) technologies requires that hurdles related to their perceived environmental effects are better understood, characterized, and mitigated [1,2]
A key environmental stressor of concern is the acoustic impacts of MRE, given that sound is an important mechanism via which marine animals find prey, communicate, and engage in social behavior
With the bottom device and surface buoy, real-time acoustic observing system (RAOS) requires a doubling of deployment and recovery effort, with the further constraint that the measurement consists of only a single spatial measurement of acoustic pressure
Summary
The market acceleration and adoption of marine renewable energy (MRE) technologies requires that hurdles related to their perceived environmental effects are better understood, characterized, and mitigated [1,2]. Two vector-sensor based acoustic monitoring systems that were employed to provide location estimates of vocalizing baleen whales are those designed by Greene et al [5] and D’Spain et al [9] These systems, with vector sensors spaced several kilometers apart [5] or that contain a single vector sensor [9] are not fit-for-purpose systems built to monitor and measure MRE noise. The acoustic vector sensors are sensitive to acoustic frequencies in the 50 Hz–3 kHz range, with a flat frequency response on the pressure channel, and a peak in the response at 1 kHz on the particle velocity channels This frequency range is suited to measurement of sounds from MRE installations that primarily emit sound below 500 Hz [11] and marine mammals whose hearing sensitivities fall within this frequency range (50 Hz–3 kHz). In-water tests indicate that the hardware configuration is suitable for small-vessel (8 m) operations in quiescent, energetic, and deep-water environments
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