Effects of ocean thermocline variability on noncoherent underwater acoustic communications

Siderius, Martin; Porter, Michael B.; Hursky, Paul; McDonald, Vincent K.

doi:10.1121/1.2436630

Cited by 72 publications

(57 citation statements)

References 13 publications

(12 reference statements)

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“…Reflection and refraction are produced when there is a change in the sound transmission media, for example: shading caused by bottom topography, effects of submerged structures (rocks, kelp, corals), reflection with the water surface, with the shore and with different density layers in the water column, like the thermocline (Topping et al 2006). While in some cases the thermocline can act as a sound channel that enhances detection efficiency (Siderius et al 2007), some studies report lower detection efficiency when the thermocline is stronger (Singh et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Topography and biological noise determine acoustic detectability on coral reefs

2013

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Acoustic telemetry is an increasingly common tool for studying the movement patterns, behaviour, and site fidelity of marine organisms, but to accurately interpret acoustic data, the variability, periodicity and range of detectability between acoustic tags and receivers must be understood. The relative and interactive effects of topography with biological and environmental noise have not been quantified on coral reefs. We conduct two long-term range tests (one and four months duration) on two different reef types in the central Red Sea, to determine the relative effect of distance, depth, topography, time of day, wind, lunar phase, sea surface temperature and thermocline on detection probability. Detectability, as expected, declines with increasing distance between tags and receivers, and we find average detection ranges of 530 and 120 m, using V16 and V13 tags respectively, but the topography of the reef can significantly modify this relationship, reducing the range by ~70%, even when tags and receivers are in line-of-sight. Analyses that assume a relationship between distance and detections must therefore be used with care. Nighttime detection range was consistently reduced in both locations and detections varied by lunar phase in the four month test, suggesting a strong influence of biological noise (reducing detection probability up to 30%), notably more influential than other environmental noises, including wind-driven noise, which is normally considered important in open-water environments. Analysis of detections should be corrected in consideration of the diel patterns we find, and range tests or sentinel tags should be used for more than one month to quantify potential changes due to lunar phase. Some studies assume that the most usual factor limiting detection range is weather-related noise; this cannot be extrapolated to coral reefs.

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Section: Introductionmentioning

confidence: 99%

Topography and biological noise determine acoustic detectability on coral reefs

2013

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“…Normalized data fitted to a negative exponential distribution showed how close the decline in fish detections was to a constant rate. In other comparisons, analysis of variance (ANOVA), correlation, and standard nonparametric tests (e.g., Mann-Whitney [MW] and Kruskal-Wallis [KW]) were used to analyze patterns in fish movements over time and in relation to body size and habitat (Siegel and Castellan, 1988).…”

Section: Discussionmentioning

confidence: 99%

“…This configuration reduced acoustic effects on signal reception from the thermocline (Siderius et al, 2007). Weighted with a concrete anchor, the receivers were fitted with an ORE Offshore SWR acoustic release transponder (EdgeTech, West Wareham, MA) that detached and allowed the receivers to float to the surface when a coded acoustic signal was transmitted.…”

Section: Receiversmentioning

confidence: 99%

Acoustic tagging and monitoring of cultured and wild juvenile crimson jobfish (Pristipomoides filamentosus) in a nursery habitat

Parrish¹,

Hayman²,

Kelley³

et al. 2015

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Abstract-The movements of cultured (n=18) and wild (n=28) juvenile crimson jobfish (Pristipomoides filamentosus) are reported for a known nursery off windward Oahu, Hawaii. The 2 batches of fish were tagged with acoustic transmitters in separate years (2006, 2007) and monitored with a receiver array for up to 10 weeks. Of the cultured fish, 75% left the nursery within 3 days, more than twice the exit rate for wild fish tagged the following year. The number of wild fish detected peaked during daylight hours, indicating that the fish were diurnally active. Tidally driven changes in bottom temperature did not explain the behavioral patterns of the wild fish that remained in the nursery for multiple weeks. Additional receivers deployed on the slope adjacent to the nursery detected that twothirds of the wild fish departed from the nursery after a short period (mean: 1.2 days [SD 1.69]), by crossing areas with soft substrate similar to that of the nursery. In contrast, the fish that exited by rock ledges stayed near the rock ledges longer (mean: 13.3 days [SD 20.9]). These movement patterns provide insight into the early life history of this deepwater snapper and a glimpse at some of the challenges for future stock enhancement efforts.

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“…ISI results in serious distortion of communication signals and makes demodulation difficult [2]. Thus, the ISI causes significant degradation in communication performance [3][4][5][6]. In addition, the temporal variations in communication channels resulting from sea surface movement and source/receiver movements result in a short coherent time and large Doppler spread, which degrade communication performance [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Estimate of Passive Time Reversal Communication Performance in Shallow Water

et al. 2017

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Time reversal processes have been used to improve communication performance in the severe underwater communication environment characterized by significant multipath channels by reducing inter-symbol interference and increasing signal-to-noise ratio. In general, the performance of the time reversal is strongly related to the behavior of the q-function, which is estimated by a sum of the autocorrelation of the channel impulse response for each channel in the receiver array. The q-function depends on the complexity of the communication channel, the number of channel elements and their spacing. A q-function with a high side-lobe level and a main-lobe width wider than the symbol duration creates a residual ISI (inter-symbol interference), which makes communication difficult even after time reversal is applied. In this paper, we propose a new parameter, E q , to describe the performance of time reversal communication. E q is an estimate of how much of the q-function lies within one symbol duration. The values of E q were estimated using communication data acquired at two different sites: one in which the sound speed ratio of sediment to water was less than unity and one where the ratio was higher than unity. Finally, the parameter E q was compared to the bit error rate and the output signal-to-noise ratio obtained after the time reversal operation. The results show that these parameters are strongly correlated to the parameter E q .

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Effects of ocean thermocline variability on noncoherent underwater acoustic communications

Cited by 72 publications

References 13 publications

Topography and biological noise determine acoustic detectability on coral reefs

Topography and biological noise determine acoustic detectability on coral reefs

Acoustic tagging and monitoring of cultured and wild juvenile crimson jobfish (Pristipomoides filamentosus) in a nursery habitat

Estimate of Passive Time Reversal Communication Performance in Shallow Water

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