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Acoustic interferometer

About: Acoustic interferometer is a(n) research topic. Over the lifetime, 1493 publication(s) have been published within this topic receiving 19355 citation(s).

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Abstract: Negative refraction of acoustic waves in two-dimensional phononic crystals has been demonstrated through both analysis and exact numerical simulation. The methods to achieve this behavior have been discussed. A microsuperlens for acoustic waves has also been designed. It is shown that refractive devices based on phononic crystals behave in a manner similar to that of optical systems. Therefore, a negative square root of the effective density or negative refraction index for acoustic waves can be introduced to describe this phenomena very well as the case of electromagnetic waves in the photonic crystals.

365 citations

Journal ArticleDOI
Abstract: Radiofrequency waves at 15 and 45 Mc are transduced into pressure waves at the same frequencies, and are applied to a CdS crystal. The waves are then converted by a second transducer into a r-f output wave. The signal amplification is found as a function of the illumination intensity on the crystal, and the electric field parallel to the pressure waves. Positive gain may be attained for suitable values of the electric field. (T.F.H.)

341 citations

Journal ArticleDOI
01 Aug 1979
Abstract: Acoustic waves in liquids are known to have wavelengths comparable to that of visible light if the frequency is in the gigahertz range. The phenomena of Brillouin scattering in liquids is based on such waves. In helium near 2 K acoustic waves with a wavelength of 2000 A were studied some ten years ago at UCLA. It follows from these observations that an imaging system based on acoustic radiation with a resolving power competitive with the optical microscope is within reach if an ideal lens free from aberrations could be found. Such a lens, which was so elusive at the beginning, is now a simple device and it is the basic component in the acoustic microscope that forms the basis for this review. In this article we will establish the characteristic properties of this new instrument. We will review some of the simple properties of acoustic waves and show how a single spherical surface formed at a solid liquid interface can serve as this ideal lens free from aberrations and capable of producing diffraction limited beams. When this is incorporated into a mechanical scanning system and excited with acoustic frequencies in the microwave range images can be recorded with acoustic wavelengths equal to the wavelength of visible light. We will present images that show the elastic properties of specimens selected from the fields of material science, integrated circuits, and cell biology. The information content in these images will often exceed that of the optical micrographs. In the reflection mode we illuminate the smooth surface of a crystalline material with a highly convergent acoustic beam. The reflected field is perturbed in a unique way that is determined by the elastic properties of the reflecting surface and it shows up in the phase of the reflected acoustic field. There is a distinct and characteristic response at the output when the spacing between the object and the lens is varied. This behavior in the acoustic ieflection microscope provides a rather simple and direct means for monitoring the elastic parameters of a solid surface. It is easy to distinguish between different materials, to determine the layer thickness, and to display variations in the elastic constants on a microscopic scale. These features lead us to believe there is a promising future for the field of acoustic microscopy.

290 citations

Journal ArticleDOI
TL;DR: The simplified results of several theoretical derivations are presented and employed in illustrative calculations and plots to ascertain the importance of nonlinear effects in applications involving plane waves, spherically diverging waves, and spheric converging waves.
Abstract: Some fundamentals of nonlinear acoustics are reviewed to facilitate their consideration in biomedical ultrasound. The phenomena described include acoustic nonlinearity, finite amplitude distortion, shock formation, harmonic components, nonlinearly induced absorption, saturation, and the influence of these effects on ultrasonic beams. The simplified results of several theoretical derivations are presented and employed in illustrative calculations and plots. These maybe used to ascertain the importance of nonlinear effects in applications involving plane waves, spherically diverging waves, and spherically converging (focused) waves. A discussion of relevant experiments is given, along with some comments on possible consequences in diagnostic, surgical, and theraputic applications.

272 citations

Abstract: The transit time of acoustic waves between a generator and a receiver positioned across a fluid chamber is determined by generating acoustic waves using a self-purging pneumatic sound generator, a transducer adjacent the outlet of the sound generator, and a receiving transducer positioned away from the sound generator outlet so that the acoustic waves received by the receiving transducer pass through a portion of the fluid. The electrical signals generated by the transmitting transducer and the receiving transducer are processed to obtain the impulse response of these electrical signals, and the point of maximum value is determined. This point of maximum value corresponds to the arrival time of the acoustic waves at the receiving location. The transit time determination may be used to calculate the fluid temperature or other parameters. The pneumatic sound generator is driven by a compressed air source so that the generator is automatically purged of any contaminants in the process of generating the random acoustic noise.

259 citations

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