We have developed a technique in ultrasonic correlation spectroscopy called diffusing acoustic wave spectroscopy (DAWS). In this technique, the motion of the scatterers (e.g., particles or inclusions) is determined from the temporal fluctuations of multiply scattered sound. In DAWS, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the auto...

AR = cavity aspect ratio a = speed of sound b = cavity half-width ~ C = dynamic compressibility c = phase speed cp = specific heat at constant pressure f = frequency H = cavity depth k = wave number m = propagation constant P = pressure Pr = Prandtl number R = reflection coefficient p = acoustic pressure pi = initial pulse amplitude Re = acoustic Reynolds number s = cavity spacing T = temperatu...

Scientific objective of this research is to understand acoustic wave propagation in a dynamic environment in two different frequency bands: (a) Low frequency band (50 Hz to 500 Hz). The subject of interest in this band is to assess the effect of environment anisotropy on acoustic wave propagation, with an emphasis on the separation of different effects due to horizontal refraction and mode coup...

from the early 1950s, estimating the autocorrelations of polynomials with coefficients on the unit circle has found applications in ising spin systems and in surface acoustic wave designs. in this paper, a technique is introduced that not only estimates the autocorrelations, but for some special types of such polynomials, it locates the frequencies at which maximum autocorrelation occurs.

Flow disturbances are generated inside a duct via pulsed injection of helium into a flow of air. This leads to the generation of an acoustic pulse (direct noise), as well as the production of entropic and compositional inhomogeneities which are convected with the mean flow. As these inhomogeneities are convected through a choked nozzle, they generate indirect noise. The resulting acoustic press...

We demonstrate that the tunable potential introduced by a surface acoustic wave on a homogeneous polariton condensate leads to fragmentation of the condensate into an array of wires which move with the acoustic velocity. Reduction of the spatial coherence of the condensate emission along the surface acoustic wave direction is attributed to the suppression of coupling between the spatially modul...

Four thin-film adhesion characterization methods are proposed. Two of them are surface acoustic wave based and the two others emphasize the complementary nature between acoustic microscopy, scratch test and tensile experiments. A continuous wave scanning acoustic microscope was used to propagate surface modes in the specimen and to measure the surface acoustic wave velocity as a function of the...

Human voice production is studied as an acoustic process inside the vocal tract using the wave equation for air, and compared with large-scale databases of simultaneously acquired microphone and electroglottograph signals. The following theories are confirmed: For voiced sounds, the process starts at glottal closures. Immediately before a glottal closure, there is a continuous airflow in the vo...