Time-domain simulations of sound propagation in a stratified atmosphere over an impedance ground

Abstract

Milk contaminated with melamine resulted in an important health hazard that affected many babies in China recently. Ultrasonic characterization of adulterated milk may detect gross levels of melamine contamination. Sound speed and density measurements were made in skim milk as a function of melamine adulteration. An ultrasonic measurement technique to implement milk quality control is discussed.

Time-Domain Simulations of Outdoor Sound Propagation with Suitable Impedance Boundary Conditions

“…It was shown by Cotté and Blanc-Benon [15,36] that a good agreement is found for the sound pressure level between the FDTD numerical simulations and calculations using a parabolic equation code through the frequency band of interest in the case of the grass impedance model. To clarify the different contributions, a good approach is to consider a ray-tracing calculation.…”

“…This former approach was used by Cotté et al [2], who proposed a TDBC for outdoor sound propagation based on a recursive convolution method originally developed in the context of electromagnetic propagation [14] and introduced in acoustics by Reymen et al [11]. It was shown that this TDBC is accurate and computationally efficient [15].…”

“…Cotté et al [2] compared different methods to identify the coefficients A k and k of Eq. (12) and proposed an optimization method in the frequency domain that ensures accurate numerical results [2,15]. Two impedance models will be investigated here:…”

Design of broadband time-domain impedance boundary conditions using the oscillatory-diffusive representation of acoustical models

“…TDIBCs, whose development can be traced back to the early 90s, are an attempt to deal with these two difficulties, by providing simple yet broadly applicable numerical impedance models, as well as efficient numerical methods to tackle convolutions. They have found use in several areas, such as duct acoustics, 7 outdoor sound propagation, 8 and room acoustics. 9 The earliest numerical impedance models were comprised of a single polynomial or rational fraction, which yields in the time domain an ordinary differential equation (ODE) between the acoustic pressure and normal velocity.…”

“…Borrowed from the computational electromagnetic community, 13 so-called "recursive" (recurrent) convolution techniques have been employed by many authors. 14,15,16,8,17 Bin et al 18 used an alternative implementation, relying instead on N additional differential equations. A comprehensive study by Dragna et al 19 showed the benefit of this technique, known as the auxiliary differential 1 Electronic mail: florian.monteghetti@onera.fr 1 equations method, over recursive convolution.…”