scholarly journals Acoustic scattering from density and sound speed gradients: Modeling of oceanic pycnoclines

2012 ◽  
Vol 131 (1) ◽  
pp. EL54-EL60 ◽  
Author(s):  
Tetjana Ross ◽  
Andone C. Lavery
Keyword(s):  
Sound Speed ◽  
Acoustic Scattering

scholarly journals Material properties of Northeast Pacific zooplankton

2014 ◽  
Vol 71 (9) ◽  
pp. 2550-2563 ◽  
Author(s):  
Kaylyn N. Becker ◽  
Joseph D. Warren
Keyword(s):  
Sound Speed ◽  
Larval Fish ◽  
Acoustic Scattering ◽  
Geographic Location ◽  
Geographic Area ◽  
Zooplankton Biomass ◽  
Density Contrast ◽  
Northeast Pacific ◽  
Dimensional Measurements ◽  
The Mean

Abstract We measured the density and sound speed contrasts relative to seawater of Northeast Pacific zooplankton. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation (s.d.) for euphausiid density contrast were 1.059 ± 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area ∼4–10 d apart were significantly higher (p< 0.001). Sound speed contrast (h) was measured for euphausiids and pelagic decapods (S. similis) and it varied between taxa. The mean and s.d. for euphausiid sound speed were 1.019 ± 0.009. Euphausiid mass was calculated from measured density and volume, and a relationship between euphausiid mass and length was produced. We determined that euphausiid volume could be accurately estimated from two-dimensional measurements of animal body shape, and that biomass (or biovolume) could be accurately calculated from digital photographs of animals. Data from this study can improve the accuracy of theoretical acoustic scattering models for these taxa, resulting in more accurate estimates of zooplankton biomass in this region.

scholarly journals Modelling acoustic scattering, sound speed, and attenuation in gassy soft marine sediments

2016 ◽  
Vol 140 (1) ◽  
pp. 274-282 ◽  
Author(s):  
A. Mantouka ◽  
H. Dogan ◽  
P. R. White ◽  
T. G. Leighton
Keyword(s):  
Marine Sediments ◽  
Sound Speed ◽  
Acoustic Scattering

scholarly journals Variability in the density and sound-speed of coastal zooplankton and nekton

2009 ◽  
Vol 67 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Krissy A. Forman ◽  
Joseph D. Warren
Keyword(s):  
Sound Speed ◽  
Fundulus Heteroclitus ◽  
Acoustic Scattering ◽  
Large Area ◽  
Palaemonetes Pugio ◽  
Acoustic Data ◽  
Abundance Estimates ◽  
Short Period ◽  
Crangon Septemspinosa ◽  
Animal Size

Abstract Forman, K. A., and Warren, J. D. 2010. Variability in the density and sound-speed of coastal zooplankton and nekton. – ICES Journal of Marine Science, 67: 10–18. Acoustic sampling techniques provide an advantage over traditional net-sampling by increasing scientist ability to survey a large area in a relatively short period, as well as providing higher-resolution data in the vertical and horizontal dimensions. To convert acoustic data into measures of biological organisms, physics-based scattering models are often used. Such models use several parameters to predict the amount of sound scattered by a fluid-like or weakly scattering animal. Two important input parameters are the density (g) and sound-speed (h) contrasts of the animal and the surrounding seawater. The density and sound-speed contrasts were measured for coastal zooplankton and nekton species including shrimps (Palaemonetes pugio and Crangon septemspinosa), fish (Fundulus majalis and Fundulus heteroclitus), and polychaetes (Nereis succinea and Glycera americana) along with multiple physiological and environmental variables. Factors such as animal size, feeding status, fecundity, gender, and maturity caused variations in g. The variations in g observed for these animals could lead to large differences (or uncertainties) in abundance estimates based on acoustic scattering models and field-collected backscatter data. It may be important to use a range of values for g and h in the acoustic scattering models used to convert acoustic data into estimates of the abundance of marine organisms.

scholarly journals Material properties of North Atlantic cod eggs and early-stage larvae and their influence on acoustic scattering

2003 ◽  
Vol 60 (3) ◽  
pp. 508-515 ◽  
Author(s):  
Dezhang Chu ◽  
Peter H. Wiebe ◽  
Nancy J. Copley ◽  
Gareth L. Lawson ◽  
Velmurugu Puvanendran
Keyword(s):  
Sound Speed ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Early Stage ◽  
Acoustic Scattering ◽  
Acoustic Properties ◽  
Target Strength ◽  
Two Fluids ◽  
Acoustic Signatures ◽  
Series Of Experiments

Abstract To study the acoustic signatures of Atlantic cod (Gadus morhua) at different biological stages from eggs to early-stage larvae (<37 days post-hatch), we conducted a series of experiments to estimate their sound-speed and density contrasts. A laboratory version of the “Acoustic Properties of Zooplankton” system was used. Sound speed was estimated by means of travel time between two transducers using a broadband acoustic signal (∼300–600 kHz). Density was estimated using a dual-density method in which two fluids of different densities were employed. It was found that the density contrasts of cod eggs and early-stage larvae were nearly all slightly less than unity (0.969–0.998), while the effective sound-speed contrasts were only slightly greater than unity (1.017–1.024) for eggs and yolk-sac stage larvae (<5 days post-hatch), and increased significantly (>1.130) for larvae older than 16 days. This change in sound-speed contrast reflected the transition of the swimbladder from an uninflated state to an inflated state. The regression relation between estimated target strength at 500 kHz and larval length in centimetres was found to be TS = 176.1 log10L − 82.4(dB). The inflation ratio of the swimbladder for early-stage larvae was an exponential function of time. The predicted period of time until full swimbladder inflation was 43.3 days.

scholarly journals The acoustic characteristics of three jellyfish species: Nemopilema nomurai, Cyanea nozakii, and Aurelia aurita

2009 ◽  
Vol 66 (6) ◽  
pp. 1233-1237 ◽  
Author(s):  
Miyuki Hirose ◽  
Tohru Mukai ◽  
Doojin Hwang ◽  
Kohji Iida
Keyword(s):  
Sound Speed ◽  
Acoustic Scattering ◽  
Aurelia Aurita ◽  
Target Strength ◽  
Bell Diameter ◽  
Nemopilema Nomurai ◽  
Acoustic Characteristics ◽  
Diameter Range ◽  
Jellyfish Species ◽  
Density Methods

Abstract Hirose, M., Mukai, T., Hwang, D., and Iida, K. 2009. The acoustic characteristics of three jellyfish species: Nemopilema nomurai, Cyanea nozakii, and Aurelia aurita. – ICES Journal of Marine Science, 66: 1233–1237. Reports about jellyfish damaging nets and reducing fish catches are increasing, and data on the abundance and distribution of various jellyfish species are needed to forecast where and when their blooms will happen. Acoustic techniques can be used to obtain this information if the acoustic characteristics of the targets are known. This is a study of acoustic scattering from three jellyfish species: Nemopilema nomurai (order Rhizostomeae), Cyanea nozakii (Semaeostomeae), and Aurelia aurita (Semaeostomeae). Target strength (TS) at 38, 120, and 200 kHz, specific density, and sound speed were measured with live specimens. Specific densities were measured using the displacement–volume–weight and the dual-density methods. The sound speeds were estimated using the time-of-flight method. The reduced TS (RTS), i.e. the TS normalized by bell area, was smaller for N. nomurai (bell diameter range 19–38 cm) than for C. nozakii (bell diameter range 30–40 cm), and the differences in RTS between the species were 17.8, 12.6, and 5.8 dB at 38, 120, and 200 kHz, respectively. The respective sound-speed contrast h and density contrast g were 1.0008 ± 0.009 (mean ± s.d.) and 1.004 ± 0.015 for N. nomurai; 1.038 and 1.073 for one C. nozakii; and 1.0001 ± 0.025 and 0.989 ± 0.019 for A. aurita.

Effect of Nada Yoga on Hypertension & Anxiety Level

GIS Business ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. 1-16
Author(s):  
Naveen Kumar ◽  
Kuldeep singh
Keyword(s):  
Sound Speed ◽  
Anxiety Level ◽  
Hatha Yoga ◽  
Significant Difference ◽  
The Subject ◽  
Level Of Significance

In Nada yoga the sound speed of an object vibrates (as well as its size, however infinitesimal) contributes to its particular sound. Different tone and frequencies contains the subject of meditation in Nada Yoga, which also takes into consideration the musical intervals used in music and in the musical recitation of mantras, is brought together with meditation techniques and certain Hatha Yoga practices that are conducive to sonic exploration. Recently a study conducted on anxiety and hypertension level in Raigarh entitled as “The effect of Nada Yoga on Hypertension and anxiety level”.  The outcome of the study shows that Nada Yoga significantly reduces Anxiety as well as Hypertension. Results founds were surprisingly shows a significant difference between the two means, at .01 level of significance. It shows how Nada Yoga can effectively help to reduce anxiety and hypertension as well as many improves in health also.

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