In this paper, the elastic properties of passive materials (matching, backing and lens materials) for ultrasound transducers are explored at room temperature in the frequency range of 25-65MHz using the ultrasonic spectroscopy method. AlurninaJEPOTEK 301 and tungsten/EPO-TEK 301 composites were fabricated and measured. Experimental results display a monotonic rise in acoustic impedance of the c...

It ha been proved that the lattice Boltzmann Methods (LBMs) are very efficient for computational fluid dynamics purposes, and for capturing the dynamics of weak acoustic fluctuations. Especially, the multi-relaxation-time lattice Boltzmann method (MRT-LBM) appears as a very robust scheme with high precision. It is well-known that there exist several free relaxation parameters in the MRT-LBM. Al...

To investigate and understand basic properties of non-radial solar p-modes with high wave numbers l, it is sufficient to consider only the outer layers of the sun. As an atmosphere, the upper part of the convection zone may be approximated by a plane layer with constant gravity. A simple standard model is a polytropic convection zone with an overlying isothermal atmosphere. In this case, the ad...

This paper considers the extension of the frequency application range of the finite element method (FEM) applied to steady-state acoustic problems. This is achieved by the hybrid coupling of the FEM with the wave based method (WBM). The WBM is a computationally efficient alternative for the FEM, but it is restricted to acoustic problems of moderate geometrical complexity. The hybrid finite elem...

Acoustic backing-off was recently proposed as an operationalisa­ tion of missing feature theory for increased recognition robustness. Acoustic backing-off effectively removes the detrimental influence of outlier values from the local decisions in the Viterbi algorithm without any kind of explicit outlier detection. In the context of con­ nected digit recognition over telephone lines, it is show...

We present a novel approach for optimizing acoustic parameters using sensitivity analysis for computer-aided design and analysis of architectural models. Our approach builds on recent low-dispersion wave-based acoustic solvers that can accurately compute the pressure field in large models. We present an efficient technique to compute the gradient of the pressure field using automatic differenti...

A compact femtosecond dual-oscillator pump-probe setup with 48 MHz-repetition rate, relying on asynchronous optical sampling, is presented. The relative timing jitter between both lasers over the whole pump-probe delay range is of the order of or lower than 500 fs. We demonstrate that both a picosecond temporal resolution and a 48 MHz spectral resolution combined with the fast acquisition rate ...

Noise is an audible acoustic energy that adversely affects the health, physiological and psychological well being of the individuals or populations. One of the major pollutants from gas flaring is the noise emanating from gas flaring stations in the Niger – Delta area of Nigeria. Noise dispersion produces many adverse effects on man and animals. Experimental analysis of noise dispersion and wea...

This paper presents an analytical and numerical study on the dispersion properties of an Euler–Bernoulli beam immersed in a steady fluid flow with periodic arrays of airfoilshaped vibration absorbers attached to it. The resonance characteristics of the airfoils generate strong attenuation of flexural waves in the beam occurring at frequencies and numerical tools are developed to investigate the...