Numerical Simulation Of Acoustic Propagation Research Articles

A numerical and experimental study of micrometeorological effects on urban sound propagation

In this work, the influence of micrometeorological effects on sound propagation in an urban street canyon is investigated numerically and experimentally. Numerical simulations of acoustic propagation are based on sound particle propagation simulation method. Numerical data are generated for urban street canyons of various widths and height ratios. Experimental data are obtained from longitudinal measurements of urban street canyons in the United States. Temperature and wind profiles are obtained from ultrasonic anemometers and thermocouples. Measurements within and outside the street canyon are of particular interest. The experimental data are useful in integrating micrometeorological effects into the acoustic propagation model. Preliminary numerical results and measurements are presented and discussed.

Numerical Simulation of Acoustic Propagation in Gas Ultrasonic Flowmeter

Numerical Simulation of Acoustic Propagation in Gas Ultrasonic Flowmeter

Probability distributions of sonic boom noise metrics in isotropic turbulent fields

Sonic boom waveform distortion caused by isotropic turbulence is examined with numerical simulations of acoustic propagation through randomly generated 3D turbulent fields. A recently developed planar, one way acoustic propagation code is used in this study to simulate the propagation of sonic boom waveforms. Computations of the signal account for diffraction, signal scattering by turbulence, nonlinear distortion, and absorption. Two types of waveforms are considered, one type is an N-wave and the other is a shaped boom. The intensity of the turbulent field is systematically varied for each set of simulations. For each condition, simulations through hundreds of randomly generated fields are conducted to obtain the statistical means and variances of PL, ISBAP, and select weighted SEL metrics. The computational results provide insight on the dependence of the probability distribution of each metric on the turbulence intensity and propagation distance. The data is further examined to compute probability density functions for each metric as a function of the turbulence intensity at different propagation distances. These functions provide insight on the effects of turbulence on the loudness levels of sonic booms. Future work and applicability of the results to atmospheric boundary layer turbulence is considered. [NASA Fellowship Activity Grant No. 80NSSC19K1685.]

On verification of the new criterion of adiabaticity by numerical simulation of acoustic propagation through the polar front

To assess the adiabaticity of acoustic propagation in the ocean is very important for acoustic field calculation (forward problem) and tomographic retrieving (inverse problem). A new criterion of adiabaticity is proposed recently (Shang et al., 2001). In this paper, numerical simulation has been conducted for acoustic propagation through the Polar Front to verify the new criterion. Numerical results on the f (frequency)-m (mode number) plan demonstrate that the new criterion works very well for this extremely non-gradual ocean structure.

Acoustic diagnostic for the polar front

The Polar frontal zone is known to have the highest contrast between properties of the divided water masses in Nordic seas. Acoustically, it is a strongly range-dependent environment. Numerical simulations of acoustic propagation in the frequency range of 20–200 Hz have been conducted for typical cases by using the IFD-PE and KRAKEN codes. The adiabaticity is strongly frequency dependent. For lower frequency, the inverted results of the frontal parameters based on the adiabatic modal travel time and modal horizontal refraction data can be obtained analytically using a simple ‘‘few parameter model’’ proposed by Kuz’kin [Acoust. Phys. 39(4), 402 (1993)]. The possibility of estimating the frontal parameters for a more complex realistic model will also be discussed. [Work supported by ONR and NOAA.]

Numerical simulation of acoustic propagation at a fluid-solid interface

Propagation of acoustic pulses in the neighborhood of the interface between fluid and solid half-spaces is investigated numerically using the finite difference technique. The solid half-space may be homogeneous, or it may comprise several distinct solids of differing acoustical properties. The solid-solid interface may have arbitrary orientation with respect to the fluid-solid interface. Plots of the displacement fields clearly illustrate the wavefronts, headwaves, and surface modes near the fluid-solid interface. In the case of the inhomogeneous solid, reflection, transmission, and mode conversions at the solid-solid interface, and subsequent interactions with the fluid-solid interface give rise to a multiplicity of decay pulses. The origin and physical significance of each of these decay pulses is made evident by the displacement field pilots.