Methods of measuring ultrasonic wave velocity in an elastic sample require data on the thickness of the sample and/or the distances between the transducers and the sample. The uncertainty of the ultrasonic wave velocity measurements generally depends on that of the data available. Conversely, to determine the thickness of a material, it is necessary to have a priori information about the wave v...

Expressions governing coherence scales of sound passing through a moving packet of nonlinear internal waves in a continental shelf environment are presented. The expressions describe the temporal coherence scale at a point, and the horizontal coherence scale in a plane transverse to the acoustic path, respectively. Factors in the expressions are the wave packet propagation speed, wave packet pr...

A theoretical analysis of radial wave thermoacoustic engines in cylindrical resonators is developed. Impedance and pressure translation equations are presented for open sections of the resonator and for heat exchangers. Coupled first-order differential equations are given for pressure and impedance in the temperature gradient supporting engine section ~stack!. These quantities are used to calcu...

Design, development and testing of transducers for creating spiral waves for underwater navigation The use of spiral waves for underwater acoustic navigation has received much attention in recent years. A spiral wave is characterized as a diverging wavefront that is omnidirectional by magnitude but with a phase that varies linearly by azimuthal angle. Such a signal may be exploited in underwate...

The underlying approach combines field observations of wave-induced bubbles and ambient noise in the top meter of the marine boundary layer with models for wave noise generation. The field studies are organized around a bubble plume sensing system, consisting of an optical bubble counter, a depth sensor, a hydrophone and an underwater video camera. The plume sensing system is mounted on a surfa...

The feasibility of exciting a localized X-wave pulse from a finite aperture is addressed. Also, the possibility of using a finite-time excitation of a dynamic aperture to generate a finite-energy approximation to an X-wave pulse is explored. The analysis is carried out by using a Gaussian time window to time limit the infinite X-wave initial excitation. Huygens’ construction is used to calculat...

Background Acoustics features in music and sound and their connection to body gestures have already been investigated in previous scientific studies, such in the case of musician movements while playing an instrument, or footstep sounds. It has also been proved that humans are able to visually identify emotions in gestures only as suggested for example by previous studies on musician and non-mu...

The topic of covert acoustical communication in air has produced public attention, lately. In 2013, we presented the fact that infected drones (e.g. laptops) might form covert acoustical mesh networks in air, only utilizing the built-in speakers and microphones. In this article, we aim to present the current state of covert acoustical communication in air. We discuss future forms of covert acou...

Marine diesel engine is essential on a ship, but emits extremely loud noise harmful to human hearing. Therefore, it mandatory use silencers reduce the venting of marine engine. An advanced silencer with new acoustical element curved tube, along perforated holes, presented suppress wave. To predict silencer's performance for high-order waves, finite model was built using COMSOL. The influence re...