scholarly journals The Effect of Mesoscale Eddy on the Characteristic of Sound Propagation

2021 ◽  
Vol 9 (8) ◽  
pp. 787
Author(s):  
Jiaqi Liu ◽  
Shengchun Piao ◽  
Lijia Gong ◽  
Minghui Zhang ◽  
Yongchao Guo ◽  
...  
Keyword(s):  
Coupling Coefficient ◽  
Satellite Images ◽  
Sound Propagation ◽  
Mesoscale Eddy ◽  
Normal Modes ◽  
Acoustic Energy ◽  
Acoustic Source ◽  
Acoustic Characteristics ◽  
North Pacific Region ◽  
Oceanic Eddy

A mesoscale eddy is detected and tracked in the western North Pacific region. Within the life cycle of the cyclonic eddies, the intensities of eddies make a difference. Satellite images indicate the oceanic eddy keeps westward-moving until it disappears. Oceanographic and acoustic characteristics of the eddy are studied. The acoustic energy distribution results from the different intensity of both modelled eddy and measured eddy are calculated. With sound propagation through the cyclonic eddy and anticyclonic eddy, the position of convergence zone moves away from and towards the acoustic source compared with the sound propagation through background hydrography. The coupling coefficient of different orders of normal modes changes significantly. The closer to the centre of the eddy, the stronger the coupling coefficient.

scholarly journals A Chebyshev-Tau spectral method for normal modes of underwater sound propagation with a layered marine environment

2021 ◽  
Vol 492 ◽  
pp. 115784
Author(s):  
Houwang Tu ◽  
Yongxian Wang ◽  
Qiang Lan ◽  
Wei Liu ◽  
Wenbin Xiao ◽  
...  
Keyword(s):  
Spectral Method ◽  
Marine Environment ◽  
Sound Propagation ◽  
Normal Modes ◽  
Underwater Sound

Range‐dependent normal modes in underwater sound propagation: Application to the wedge‐shaped ocean

1975 ◽  
Vol 58 (6) ◽  
pp. 1171-1177 ◽  
Author(s):  
R. D. Graves ◽  
Anton Nagl ◽  
H. Überall ◽  
G. L. Zarur
Keyword(s):  
Sound Propagation ◽  
Normal Modes ◽  
Underwater Sound

Multi-Modal Acoustic Flow Decomposition Examined in a Hard Walled Cylindrical Duct

2015 ◽  
Vol 39 (2) ◽  
pp. 289-296 ◽  
Author(s):  
Stefan Weyna ◽  
Witold Mickiewicz
Keyword(s):  
Acoustic Waves ◽  
Sound Propagation ◽  
Practical Interest ◽  
Sound Intensity ◽  
Wide Band ◽  
Acoustic Energy ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Circular Duct ◽  
Duct Geometry

Abstract Flow fields could be of great interest in the study of sound propagation in aeroengines. For ducts with rigid boundaries, the fluid-resonant category may contribute significantly to unwanted noise. An understanding of the multi-modal propagation of acoustic waves in ducts is of practical interest for use in the control of noise in, for example, aero-engines, automotive exhaust and heating or ventilation systems. The purpose of our experiments was to test the acoustic energy transmission of duct modes based on studies carried out by the sound intensity technique. Sound intensity patterns in circular duct are discussed of modal energy analysis with particular reference to proper orthogonal decomposition and dynamic mode decomposition. The authors try to justify some advantages of the sound intensity experimental research in this area. In the paper, the wide-band sound signal propagated from source approximated with loudspeaker in hard-walled duct is imaged using a sound intensity - based approach. For a simple duct geometry, the sound intensity field is examined visually and by performing a modal decomposition greater insight into the acoustic structures is obtained. The image of sound intensity fields below and above “cut-off” frequency region are found to compare acoustic modes which might resonate in duct.

Noise Measurements and Reduction for High-Frequency Vibrating Devices in the Application of Cooling Electronics

2012 ◽  
Author(s):  
Longzhong Huang ◽  
Terrence Simon ◽  
Min Zhang ◽  
Taiho Yeom ◽  
Mark North ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Frequency ◽  
Noise Level ◽  
Electronics Cooling ◽  
Acoustic Energy ◽  
High Heat Flux ◽  
Driving Voltage ◽  
Active Device ◽  
Acoustic Characteristics ◽  
Active Devices

Traditional heat sinks for electronics cooling have become ever more difficult to design to meet the high dissipation rate of modern high-heat-flux electronics. Active devices, especially devices operating at a high frequency, show promise toward enhancing heat transfer performance. However, active devices generate noise that may not be acceptable to personnel. The present work studies acoustic characteristics of piezoelectrically-driven synthetic jets and oscillating plate agitators operating at high frequency (around 1000 Hz) employed in an electronics cooling module for heat transfer enhancement purposes. The A-weighted noise level from such actuators is measured and found to increase with increases of driving voltage and operational frequency. The measured sound pressure level of the active devices used in our present enhanced heat transfer module can be as high as 100 dB. Through a power spectrum analysis, we find that most acoustic energy is in a narrow frequency band close to the operating frequency of the active device. To decrease the noise level, a muffler, which also allows cooling air to recirculate through the equipment cabinet, has been designed and tested. An analytical model is employed to select the geometry of the muffler for optimal performance based on acoustic characteristics of the active devices and the through-flow pressure drop. The muffler having this optimal design is fabricated and tested and found to be able to decrease the noise level generated by two actuators from 83 dB to 64 dB.

A DEDISPERSION TRANSFORM FOR SOUND PROPAGATION IN SHALLOW WATER WAVEGUIDE

2010 ◽  
Vol 18 (03) ◽  
pp. 245-257 ◽  
Author(s):  
DA ZHI GAO ◽  
NING WANG ◽  
HAO ZHONG WANG
Keyword(s):  
Fourier Transform ◽  
Data Processing ◽  
Shallow Water ◽  
Sound Propagation ◽  
Normal Modes ◽  
Real Data ◽  
Present Approach ◽  
Dispersive Effect

For sound propagation in a shallow water waveguide, a dedispersion transform which can remove the dispersive effect of signal is described in this paper. The transform is a modified Fourier transform with two variables: translation and dispersion. Dispersive effect of signal for normal modes can be removed when these two variables match to real parameters. The validity of the present approach is verified in simulation and real data processing.

scholarly journals Glider Sampling Simulations in High-Resolution Ocean Models

2020 ◽  
Vol 37 (6) ◽  
pp. 975-992
Author(s):  
Jacob M. Steinberg ◽  
Charles C. Eriksen
Keyword(s):  
High Resolution ◽  
Velocity Profile ◽  
Numerical Models ◽  
Mesoscale Eddy ◽  
Normal Modes ◽  
Vertical Displacement ◽  
Geostrophic Velocity ◽  
Velocity Amplitude ◽  
The Difference ◽  
Autonomous Underwater Glider

AbstractIdealized simulations of autonomous underwater glider sampling along sawtooth vertical–horizontal paths are carried out in two high-resolution ocean numerical models to explore the accuracy of isopycnal vertical displacement and geostrophic velocity profile estimates. The effects of glider flight speed, sampling pattern geometry, and measurement noise on velocity profile accuracy are explored to interpret recent full-ocean-depth Deepglider observations and provide sampling recommendations for glider missions. The average magnitude of velocity error profiles, defined as the difference between simulated glider-sampled geostrophic velocity profile estimates and model velocity profiles averaged over the spatial and temporal extent of corresponding simulated glider paths, is less than 0.02 m s−1 over most of the water column. This accuracy and the accuracy of glider geostrophic shear profile estimates are dependent on the ratio of mesoscale eddy to internal wave velocity amplitude. Projection of normal modes onto full-depth vertical profiles of model and simulated glider isopycnal vertical displacement and geostrophic velocity demonstrates that gliders are capable of resolving barotropic and baroclinic structure through at least the eighth baroclinic mode.

scholarly journals Improving the Performance of Mode-Based Sound Propagation Models by Using Perturbation Formulae for Eigenvalues and Eigenfunctions

2021 ◽  
Vol 9 (9) ◽  
pp. 934
Author(s):  
Alena Zakharenko ◽  
Mikhail Trofimov ◽  
Pavel Petrov
Keyword(s):  
Sound Propagation ◽  
Underwater Acoustics ◽  
Computational Cost ◽  
Normal Modes ◽  
Sound Field ◽  
Field Calculation ◽  
Combined Model ◽  
Eigenvalues And Eigenfunctions ◽  
Propagation Models ◽  
Area Of Interest

Numerous sound propagation models in underwater acoustics are based on the representation of a sound field in the form of a decomposition over normal modes. In the framework of such models, the calculation of the field in a range-dependent waveguide (as well as in the case of 3D problems) requires the computation of normal modes for every point within the area of interest (that is, for each pair of horizontal coordinates x,y). This procedure is often responsible for the lion’s share of total computational cost of the field simulation. In this study, we present formulae for perturbation of eigenvalues and eigenfunctions of normal modes under the water depth variations in a shallow-water waveguide. These formulae can reduce the total number of mode computation instances required for a field calculation by a factor of 5–10. We also discuss how these formulae can be used in a combination with a wide-angle mode parabolic equation. The accuracy of such combined model is validated in a series of numerical examples.

scholarly journals Review of Acoustic Sources Alternatives to a Dodecahedron Speaker

2019 ◽  
Vol 9 (18) ◽  
pp. 3705 ◽  
Author(s):  
Nikolaos M. Papadakis ◽  
Georgios E. Stavroulakis
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Transfer Functions ◽  
Acoustic Measurements ◽  
Acoustic Source ◽  
Acoustic Characteristics ◽  
Acoustic Sources ◽  
Future Work ◽  
Selection Of ◽  
Better Than

An omnidirectional source is required in many acoustic measurements. Commonly a dodecahedron speaker is used but due to various factors (e.g., high cost, transportation difficulties) other acoustic sources are sometimes preferred. In this review, fifteen acoustic source alternatives to a dodecahedron speaker are presented while emphasis is placed on features such as omnidirectionality, repeatability, adequate sound pressure levels, even frequency response, accuracy in measurement of acoustic parameters and fulfillment of ISO 3382-1 source requirements. Some of the alternative acoustic sources have the appropriate features to provide usable results for acoustic measurements, some have acoustic characteristics better than a dodecahedron speaker (e.g., omnidirectionality in the high-frequency range), while some can potentially fulfill the ISO 3382-1 source requirements. Collected data from this review can be used in many areas (e.g., ISO measurements, head-related transfer functions measurements) for the appropriate selection of an acoustic source according to the expected use. Finally, suggestions for uses and future work are given aimed at achieving further advances in this field.

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