Acoustic interferometer

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

Boundary-reflected waves and ultrasonic coda waves in rock physics experiments

Abstract: Ultrasonic coda waves are widely used to study high-frequency scattering. However, ultrasonic coda waves are strongly affected by interference from by boundary-reflected waves. To understand the effect of boundary-reflected waves, we performed ultrasonic experiments using aluminum and shale samples, and the rotating staggered-mesh finite-difference method to simulate the wavefield. We analyzed the wavefield characteristics at the different receiving points and the interference characteristics of the boundary-reflected waves with the ultrasonic coda wave, and the effect of sample geometry on the ultrasonic coda waves. The increase in the aspect ratio of the samples delays the interference effect of the laterally reflected waves and reduces the effect on the ultrasonic coda waves. The main waves interfering with the ultrasonic coda waves are laterally reflected PP-, PS-, PPP-, and PPS-waves. The scattering and attenuation of the high-frequency energy in actual rocks can weaken the interference of laterally reflected waves with the ultrasonic coda waves.

Acoustic impedance estimation using calibration curve for scanning acoustic impedance microscope

Abstract: Ultrasonic has been used since several decades ago. One of ultrasonic application is used in medical field to observe mechanical properties of target, such as speed of sound, density, acoustic impedance, attenuation, etc. Several methods are also available to estimate mechanical property of target. In the previous research, we developed Scanning Acoustic Microscope (SAM). On that research, we proposed a method to estimated acoustic impedance by utilizing calibration curve. A calibration curve is established based on echo intensity obtained from calculation of acoustic propagation. The highest amplitude of a single frequency component is chosen and taken into calculation. The other frequency components are neglected. In this paper, authors propose a method to estimate acoustic impedance of target. The acoustic impedance is estimated based on calibration curve by considering all frequency components of acoustic wave. This calculation is then compared to previous research. As a result, acoustic impedance of cerebellar tissue of rat are presented by utilizing two calibration curves.

Manipulation of acoustic waves using a functionally graded material and process for making the same

Abstract: A device for manipulation of acoustic waves is provided, comprising a functionally-graded material for interposing between a source of the acoustic waves and a target, which may be a detector of manipulated acoustic waves. The functionally-graded material has a gradient in acoustic wave velocity which is obtained by the generation of a gradient in at least one of the following properties: elastic modulus, Poisson's ratio, and density, that is perpendicular to a direction of propagation of the acoustic waves. The gradient is axial. Biaxial acoustic velocity gradients may be used for focusing/waveguiding (high-low-high) or dispersing (low-high-low), while monoaxial acoustic velocity gradients may be used for wave steering. Also in accordance with the present invention, a method of making the device is provided, comprising: (a) providing the source of acoustic waves; (b) providing the target for acoustic waves, e.g., detector of manipulated acoustic waves; (c) providing the functionally-graded material having a gradient in at least one material property; and (d) interposing the functionally-graded material between the source of acoustic waves and the target for acoustic waves such that the gradient is perpendicular to a direction of propagation of the acoustic waves. The functionally-graded material so provided can be used to manipulate, i.e., focus, disperse, steer, waveguide acoustic waves for applications such as, acoustoelectronics, acoustooptics, SONAR, ultrasonic imaging, non-destructive testing (NDT), etc.

Brillouin scattering measurements of the temperature dependence of sound velocity and acoustic absorption in simple alcohols

Abstract: A scanning Fabry–Perot interferometer was used to measure Brillouin spectra of methanol, isopropanol and a 95% ethanol–water mixture for temperatures ranging between 285 K and 320 K. The Brillouin frequency shifts and linewidths were used to calculate the velocities and absorption coefficients of hypersonic acoustic waves in these liquids. The temperature dependence of sound speed and acoustic attenuation was determined. For all three materials, both sound velocity and absorption coefficient decreased with temperature.