The influence of array vertical directivity patterns on bottom reverberation for mid to high frequency active sonar working in littoral shallow waters

2011 ◽  
Author(s):  
Songwen Li ◽  
Zhaowen Meng
Keyword(s):  
High Frequency ◽  
Shallow Waters ◽  
Active Sonar ◽  
Directivity Patterns

scholarly journals Low-cost monitoring buoys network tracking biogeochemical changes in lakes and marine environments – a regional case study

2018 ◽  
Vol 90 (10) ◽  
pp. 1631-1646 ◽  
Author(s):  
Alejandro J. Vitale ◽  
Gerardo M.E. Perillo ◽  
Sibila A. Genchi ◽  
Andrés H. Arias ◽  
María Cintia Piccolo
Keyword(s):  
High Frequency ◽  
Low Cost ◽  
Decision Makers ◽  
Shallow Waters ◽  
Global Level ◽  
Temperate Region ◽  
Coastal Marine ◽  
The Cost

AbstractLakes, rivers, estuaries and ocean waters control many important natural functions at the regional-global level. Hence, integrative and frequent long-term water monitoring is required globally. This paper describes the main features and innovations of a low-cost monitoring buoys network (MBN) deployed in a temperate region of Argentina. The MBN was designed to record extended time series at high-frequency, which is of great value for the scientific community, as well as for decision-makers. In addition, two innovative designs belonging to two versions of moored buoys (i.e. shallow waters and coastal marine waters) were presented. It was shown that the cost of either of two versions of the buoy is low, which can be considered as the main advantage.

scholarly journals SHALLOW WATERS INTERFERENCE PATTERN FEATURES AND APPLICATIONS

2015 ◽  
Vol 33 (3) ◽  
pp. 523
Author(s):  
Antonio Hugo Saroldi Chaves ◽  
Kleber Pessek ◽  
Luiz Gallisa Guimarães ◽  
Carlos Eduardo Parente
Keyword(s):  
Interference Pattern ◽  
Processing Time ◽  
Shallow Waters ◽  
Underwater Sound ◽  
Geoacoustic Inversion ◽  
High Frequencies ◽  
Active Sonar ◽  
Wave Interference ◽  
Invariant Parameter ◽  
Frequency Distance

ABSTRACT. Studies in shallow waters pointed out that the acoustic wave interference patterns have potential application in a broad range of problems in underwater acoustics such as: passive sonar, active sonar, array processing, time-reverse mirrors and geoacoustic inversion. For shallow waters underwater sound waveguides, the main features of this research is interference pattern or “striations” obtained by means of Frequency-time or Frequency-distance spectrograms. This work aims to characterize these interference pattern or striations related to “invariant” parameter β. The theory is developed based on real underwater waveguide. The present results confirm that the parameter β is frequency dependent and at high frequencies it tends to the unity. In another words, far from the waveguide cut-off frequency the present real waveguides could be treated by an ideal waveguide. Besides, in this approximation it is possible to make source-receiver passive distance predictions based on the related interference pattern.Keywords: underwater acoustic, waveguide, interference pattern.RESUMO. Estudos em águas rasas apontam que os padrões de interferência de ondas acústicas têm aplicação potencial em uma ampla gama de problemas de acústica submarina, tais como: sonar passivo, sonar ativo, processamento de arrays, espelhos de reversão temporal e inversão geoacústica. O foco principal desta pesquisa é o padrão de interferência ou estrias obtidas por meio de espectrogramas e gráficos no plano de Frequências e Distâncias. Este trabalho tem como objetivo caracterizar estes padrões de interferência ou estrias com o parâmetro invariante β. A teoria é desenvolvida com base em um guia de onda real. Os resultados deste estudo confirmam que o parâmetro β é dependente da frequência e, em altas frequências, tende à unidade. Em outras palavras, longe da frequência de corte, o comportamento do guia de onda real é semelhante ao guia de onda ideal. Além disso, nesta aproximação, é possível fazer previsões de distância passiva entre o receptor e a fonte com base no padrão de interferência.Palavras-chave: acústica submarina, guia de ondas, padrão de interferência.

Detection of Atlantic herring (Clupea harengus) schools in shallow waters using high-frequency sidescan sonars

1998 ◽  
Vol 55 (6) ◽  
pp. 1419-1429 ◽  
Author(s):  
Mark V Trevorrow ◽  
Ross R Claytor
Keyword(s):  
High Frequency ◽  
Coastal Region ◽  
Field Trials ◽  
Clupea Harengus ◽  
Target Strength ◽  
Sidescan Sonar ◽  
Shallow Waters ◽  
Atlantic Herring ◽  
Reverberation Time ◽  
Acoustic Target

This work examines results from field trials in April and May 1996 exploring the feasibility for estimating spawning Atlantic herring (Clupea harengus) abundance using a 330-kHz sidescan sonar in a shallow coastal region near Escuminac, New Brunswick. Herring schools were observed using both towed and fixed-location, azimuthally scanning techniques at ranges up to 100 m in water depths of 3-6 m. The schools were typically linear in shape, with lengths of 100-280 m, thickness of 4-14 m, and peak acoustic target strength near -12 dB. Using acoustic ray-tracing analysis, surface- and bottom-reflected multipaths from an ensemble of targets are shown to increase the echo amplitude and reverberation time, producing large overestimates (4-27 times actual) in herring densities when using echo-integration. Using the acoustic simulations to compensate for this reflection focusing, average population densities near 11 ·m-3 were estimated, with the schools comprising 10 900 - 103 000 individuals. These total school sizes and densities were consistent with expectations for spawning herring.

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