Partial dereverberation used to characterize open circuit scuba diver signatures

Abstract

The use of passive acoustics to detect self-contained underwater breathing apparatus (SCUBA) divers is useful for nearshore and port security applications. While the performance of a detector can be optimized by understanding the signal's spectral characteristics, anechoic recording environments are generally not available or are cost prohibitive. A practical solution is to obtain the source spectra by equalizing the recording with the inverse of the channel's impulse response. This paper presents a dereverberation method for signal characterization that is subsequently applied to four recorded SCUBA configurations. The inverse impulse response is computed in the least-square sense, and partial dereverberation of SCUBA is performed over the 6-18 kHz band. Results indicate that early reflections and late reverberation added as much as 6.8 dB of energy. Mean unadjusted sound pressure levels computed over the 0.3-80 kHz band were 130 ± 5.9 dB re 1 μPa at 1 m. Bubble noise carries a significant amount of the total energy and masks the regulator signatures from 1.3 to 6 kHz, depending on the regulator configuration. While the dereverberation method is applied here to SCUBA signals, it is generally applicable to other sources if the impulse response of the recording environment can be obtained separately.

Person-following by autonomous robots: A categorical overview

“…Consequently, robust visual detection and tracking become extremely difficult. Passive sonars, such as hydrophones are useful in such scenarios (Gemba et al, 2014; Hari et al, 2015). Active sonars are also used for diver-following in unfavorable visual conditions (DeMarco et al, 2013; Mandic et al, 2016).…”

“…Additionally, their usage cause disturbances to the marine ecosystem and may also be limited by government regulations on sound levels. Thus, the use of passive sonars such as hydrophones is a practical alternative (Gemba et al, 2014; Hari et al, 2015). Passive sonars capture sound waves of diver’s breaths and movements, which have inherent periodicity.…”

Clutter map detector for active diver detection sonar

“…Coastal protection and in particular port security is a subject of growing interest in the active sonar system [1–6]. Recently, numerous papers have been published on the processing for divers detection in shallow water: the Doppler sensitive pulses design for diver detection [7, 8], tracking of divers [9, 10], analysis of diver signatures [11–13] and clutter suppression [14]. Diver detection is a hard task in underwater acoustics.…”

Effects of SCUBA bubbles on counts of roving piscivores in a large remote marine protected area

“…The scientific inquiry of marine life poses unique challenges. Potential sources of bias associated with in situ visual fish surveys are numerous, including diver experience level [1,2], survey method [3], differences in fishing pressure among locations and human populations [4,5] Survey divers typically use open circuit SCUBA (OC) equipment that releases exhaust bubbles, and introduce visual disturbances and audible SCUBA exhaust, that has been measured at 90 dB [6] and can be heard by fishes as far as 200 m away [7]. This noise, in addition to the visual disturbances of the exhaust bubbles, introduce a constant and potential bias present from the first modern era in-situ fish survey [8].…”