The acoustic field is obtained in terms of the wave number integration for a horizontally stratified ocean. The Inverse Hankel Transform is obtained for shallow water over a Layered inhomogeneous elastic bottom using “Direct global Matrix approach” with Fast Field Approximation Technique. This paper presents the determination of total solution for the depth dependence of the field: the depth de...

Materials that consist of a random microstructure can affect ultrasonic measurements--reducing signal strength, increasing noise, and reducing measurement accuracy--through scattering and aberration of the acoustic field. To account for these adverse effects a phase screen model, alongside the stochastic wave equation, has been developed. This approach allows the field and study aberrations to ...

The characterization of NDE transducers involves an assessment of the bidirectional acoustoelectric conversion between electrical and acoustic terminals and an evaluation of the near and farfield radiation patterns. The internal details of the transducer are largely unknown and, consequently, the traditional techniques for analyzing the structures cannot be applied. Instead, the transducer may ...

Recent measurements of GPS-derived total electron content (TEC) reveal acoustic wave periods of ∼1–4 min in the F region ionosphere following natural hazard events, such as earthquakes, severe weather, and volcanoes. Here we simulate the ionospheric responses to infrasonic-acoustic waves, generated by vertical accelerations at the Earth’s surface or within the lower atmosphere, using a compress...

Stonehenge is the largest and most complex ancient stone circle known to mankind. In its original form, the concentric shape of stone rings would have surrounded an individual both visually and aurally. It is an outdoor space and most archaeological evidence suggests it did not have a roof. However, its large, semi-enclosed structure, with many reflecting surfaces, would have reflected and diff...

Direct numerical simulations of a turbulent boundary layer over a bump were performed to examine the effects of surface longitudinal curvature on wall pressure fluctuations (pw) and flow induced noise. Turbulence statistics and frequency spectra were obtained to elucidate the response of wall pressure fluctuations to the longitudinal curvature and to the corresponding pressure gradient. Wall pr...

This paper describes a numerical investigation of the acoustic resonance occurring at specific flow speeds when a long two-dimensional rectangular plate is placed on the centre-line of a duct. The flowMach number is sufficiently small that the flow and acoustic fields can be modelled separately; however, the effect of the acoustic field in modifying the flow field is accounted for and, in turn,...

This paper proposes a method of creating acoustic contrast control in an arc-shaped area using a linear loudspeaker array. The boundary of the arc-shaped area is treated as the envelope of the tangent lines that can be formed by manipulating the phase profile of the loudspeakers in the array. When compared with the existing acoustic contrast control method, the proposed method is able to genera...

This article presents an empirical model for the noise of the acoustic underwater channel in shallow water from the analysis of field data measurements. A probability density function for the noise amplitude distribution is proposed and the associated likelihood functions are derived. As a result, an expression to the probability of symbol error for binary signaling is presented for the channel...

This paper deals with the measurement of acoustic particle velocity and acoustic streaming velocity in a closed-loop waveguide in which a resonant traveling acoustic wave is sustained by two loudspeakers appropriately controlled in phase and amplitude. An analytical model of the acoustic field and a theoretical estimate of the acoustic streaming are presented. The measurement of acoustic and ac...