Travel time bias in 2D modeling of 3D sound propagation

3D sound propagation modeling in the context of acoustic noise monitoring problems is considered. A technique of effective source spectrum reconstruction from a reference single-hydrophone measurement is discussed, and the procedure of simulation of sound exposure level (SEL) distribution over a large sea area is described. The proposed technique is also used for the modeling of pulse signal waveforms at other receiver locations, and results of a direct comparison with the pulses observed in the experimental data is presented.

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A 2-D DESCRIPTION OF SOUND PROPAGATION IN A HORIZONTALLY-INHOMOGENEOUS OCEAN

Journal of Computational Acoustics ◽

10.1142/s0218396x02001425 ◽

2002 ◽

Vol 10 (01) ◽

pp. 123-151 ◽

Cited By ~ 14

Author(s):

OLEG A. GODIN

Keyword(s):

Travel Time ◽

Sound Propagation ◽

Environmental Gradients ◽

Normal Modes ◽

Approximate Expression ◽

Underwater Sound ◽

Mode Amplitude ◽

Geometrical Acoustics ◽

Horizontal Refraction ◽

Horizontally Inhomogeneous

Effects of horizontal refraction on underwater sound propagation in deep and shallow water are considered within geometrical acoustics and adiabatic normal modes approximations. Several distinct formulations of the adiabatic approximation have been proposed in the literature on modal propagation. These formulations differ in the predicted values of mode amplitudes and, hence, in their reciprocity and energy-conserving properties. The formulations are compared with respect to their accuracy and domain of validity, assuming small and smooth variation of mode propagation constants characteristic of underwater acoustic waveguides. Perturbation theory for horizontal (modal) rays is used in the analysis. An approximate expression for the adiabatic mode amplitude in 3-D problems is derived which requires environmental information only along the source-receiver radial and which has greater accuracy than previous formulations. It is shown that the uncoupled azimuth approximation, also known as the N × 2-D approximation, overestimates travel times of ray arrivals as well as phases of adiabatic normal modes in a horizontally-inhomogeneous ocean. The travel time and phase biases rapidly increase with the value of cross-range environmental gradients and propagation range. Simple and explicit expressions for leading-order corrections to the travel time and the phase are found in terms of path-averaged cross-range environmental gradients. Implications on applicability of the uncoupled azimuth approximation for sound propagation modeling in a horizontally-inhomogeneous ocean are discussed. A perfect-wedge model of the coastal ocean is chosen to illustrate the importance of the travel-time and phase biases due to horizontal refraction.

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3D sound spatialization with game engines: the virtual acoustics performance of a game engine and a middleware for interactive audio design

Virtual Reality ◽

10.1007/s10055-021-00589-0 ◽

2021 ◽

Author(s):

Hasan Baran Fırat ◽

Luigi Maffei ◽

Massimiliano Masullo

Keyword(s):

Virtual Environments ◽

Sound Propagation ◽

Game Engine ◽

Production Methods ◽

3D Audio ◽

3D Sound ◽

Geometrical Acoustics ◽

Game Engines ◽

Virtual Acoustics ◽

Sound Spatialization

AbstractThis study analyses one of the most popular game engines and an audio middleware to reproduce sound according to sound propagation physics. The analysis focuses on the transmission path between the sound source and the receiver. Even if there are several ready-to-use real-time auralization platforms and software, game engines' use with this aim is a recent study area for acousticians. However, audio design needs with game engines and the limits of their basic releases require additional tools (plugins and middleware) to improve both the quality and realism of sound in virtual environments. The paper discusses the use of Unreal Engine 4 and Wwise's 3D audio production methods in a set of different test environments. It assesses their performance in regard to a commercial geometrical acoustics software. The results show that the investigated version of the game engine and its sound assets are insufficient to simulate real-world cases and that significant improvements can be achieved with use of the middleware.

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Monitoring Inflow Dynamics in a Multipurpose Dam Based on Travel-Time Principle

10.21203/rs.3.rs-581117/v1 ◽

2021 ◽

Author(s):

Mohamad Basel Al Sawaf ◽

kiyosi Kawanisi ◽

Cong Xiao ◽

Gillang Noor ◽

Faruq Khadami ◽

...

Keyword(s):

Travel Time ◽

Management Practices ◽

Sound Propagation ◽

Flow Direction ◽

Slow Flow ◽

The Novel ◽

Flow Environment ◽

Dam Operation ◽

Dam Inflow ◽

Acoustic Travel Time

Abstract Understanding inflow dynamics in a dam lake forms the basis for optimal dam operation and management practices. However, methods pertaining to adequately determining negative inflows and addressing them, as well as quantifying uncertainties in dam inflow, have been scarcely investigated. In this study, the inflow was observed using two pairs of fluvial acoustic tomography (FAT) systems placed diagonally in a dam lake, forming a crossed-shaped pattern. The “travel-time” principle is the primary approach for measuring the inflow by FAT. The novelty of this study is in discussing the inflow characteristics within a slow water-flow environment monitored by FAT. Based on the reciprocal sound transmission, we upgraded an equation to estimate the flow direction; this newly proposed generalized equation can be used in a fluctuating flow environment. We also discussed the sound propagation characteristics for slow flow velocities. Finally, we demonstrated that a small inaccuracy in the acoustic signal, even by a sub-millisecond, can cause significant errors in measurements. One of the novel findings of this study is the detection of internal waves using the improved flow direction equation and acoustic travel-time records. Overall, this study presents a promising approach for inflow measurements under extremely slow flow conditions.

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Analytical Lie-algebraic solution of a 3D sound propagation problem in the ocean

Physics Letters A ◽

10.1016/j.physleta.2017.04.011 ◽

2017 ◽

Vol 381 (23) ◽

pp. 1921-1925 ◽

Cited By ~ 10

Author(s):

P.S. Petrov ◽

S.V. Prants ◽

T.N. Petrova

Keyword(s):

Sound Propagation ◽

Propagation Problem ◽

Algebraic Solution ◽

3D Sound

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Acoustic tomography in the atmospheric surface layer

Annales Geophysicae ◽

10.1007/s00585-999-0139-9 ◽

1999 ◽

Vol 17 (1) ◽

pp. 139-148 ◽

Cited By ~ 4

Author(s):

A. Ziemann ◽

K. Arnold ◽

A. Raabe

Keyword(s):

Surface Layer ◽

Travel Time ◽

Atmospheric Surface Layer ◽

Sound Propagation ◽

Measuring System ◽

Acoustic Tomography ◽

Reconstruction Technique ◽

Two Dimensional ◽

Sound Waves ◽

Atmospheric Conditions

Abstract. Acoustic tomography is presented as a technique for remote monitoring of meteorological quantities. This method and a special algorithm of analysis can directly produce area-averaged values of meteorological parameters. As a result consistent data will be obtained for validation of numerical atmospheric micro-scale models. Such a measuring system can complement conventional point measurements over different surfaces. The procedure of acoustic tomography uses the horizontal propagation of sound waves in the atmospheric surface layer. Therefore, to provide a general overview of sound propagation under various atmospheric conditions a two-dimensional ray-tracing model according to a modified version of Snell's law is used. The state of the crossed atmosphere can be estimated from measurements of acoustic travel time between sources and receivers at different points. Derivation of area-averaged values of the sound speed and furthermore of air temperature results from the inversion of travel time values for all acoustic paths. Thereby, the applied straight ray two-dimensional tomographic model using SIRT (simultaneous iterative reconstruction technique) is characterised as a method with small computational requirements, satisfactory convergence and stability properties as well as simple handling, especially, during online evaluation.Key words. Meteorology and atmospheric dynamics (turbulence; instruments and techniques).

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