Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Coupled guided acoustic modes in water-filled thin-walled tubes

Abstract: Recent results [J. D. N. Cheeke et al., J. Acoust. Soc. Am. 104, 3678 (1998)] reported a 20% decrease in group velocity for flexural mode circumferential waves propagating around water-filled thin-walled stainless-steel tubes. In the present work, the full theory of such modes is developed to explain the structure modes which originates from the coupling between the water filler and stainless tube. Calculated values of the group velocity for the first two coupled modes are in excellent agreement with experiment. The results are of interest for the physics of acoustic waves in fluid-loaded structures and have potential application for liquid level detection.

Conversion of an Acoustic Surface Pulse Into Bulk Waves at a Surface Discontinuity

Abstract: A numerical finite difference analysis is presented of the scattering of a surface acoustic pulse by a groove. From initial analytical solutions, corresponding to a particularly shaped pulse, the wavelet scattering is simulated. The evolution of displacement fields with time is shown on a set of graphic maps, which aives an easy characterization of bulk radiated modes, and an estimation of magnitude with angle. The study is completed by a spectral a nalysis of motions, wh

Passive radar apparatus

Abstract: PROBLEM TO BE SOLVED: To solve such problems that, in a conventional radar apparatus, the position of an own station is searched by radio waves in a monostatic radar apparatus whose transmission-reception is performed by the same antenna and that direct waves and reflected waves must be received respectively by separate antennas in order to receive faint reflected waves from a target in the case of a bistatic radar apparatus using radio waves whose transmission factor is unclear. SOLUTION: The direction of the direct waves and that of the reflected waves are estimated by using an ultraresolution algorithm such as MUSIC or the like for a received signal. After that, the direct waves and the reflected waves are separated and extracted from the received signal. Even when transmitted waves are used as the direct waves and even when the direct waves and the reflected waves are received by the same antenna, the distance and the direction of the target can be found, and the position of the own station can not be searched.

Ultra high frequency acoustic waves

Abstract: Two different experimental techniques are available for making ultra-high-frequency acoustic measurements. These are (i) the study of light-scattering (for solids and liquids), and (ii) the use of microwaves (so far mainly restricted to solids). The first method does not require an acoustic source or generator, but makes use of the natural Debye waves; the results show that for someliquids it is possible to observe the effects of non-elastic molecular collisions. The second method has so far been applied chiefly to quartz, but is already yielding some information on the nature of the anharmonic interactions between atoms in a crystal.

Precise measurement of phase velocity of surface acoustic waves using parallel comb filters

Abstract: An improved technique for measuring SAW velocity using parallel comb filters is reported. The measured velocity on the free surface of 36° ST-cut quartz is 3151.9 m/s. The relative standard deviation of ±57ppm means that this is currently the most precise technique to measure SAW velocity.