Broadband acoustic focusing by symmetric Airy beams with phased arrays comprised of different numbers of cavity structures

We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth（about 1.4 kHz）, high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.

Changes in Coupled Vibration Frequencies and Modes of Wall-Cavity Systems Induced by Stiffness Variation in the Structure

Problems of fluid structure interactions are governed by a set of fundamental parameters. This work aims at showing through simple examples the changes in natural vibration frequencies and mode shapes for wall-cavity systems when the structural rigidity is modified. Numerical results are constructed using ANSYS software with triangular finite elements for both the fluid （2D acoustic elements） and the solid （plane stress） domains. These former results are compared to proposed analytical expressions, showing an alternative benchmark tool for the analyst. Very rigid wall structures imply in frequencies and mode shapes almost identical to those achieved for an acoustic cavity with Neumann boundary condition at the interface. In this case, the wall behaves as rigid and fluid-structure system mode shapes are similar to those achieved for the uncoupled reservoir case.

Outer cavity Janus-Helmholtz underwater acoustic transducer

The outer cavity Janus-Helmholtz with sound insulation layer is presented for ob- taining the capacity of high-power non-directional transmitting. The radiation efficiency and directivity in the 0 degrees direction can be improved when the radiation mode is changed by laying sound insulation layer. The operating bandwidth can be expanded effectively by the dual mode coupling between the cavity vibration and longitudinal vibration of Janus transducer. A prototype is designed by finite element method. Test results show that the results are in good agreement with the design results. Compared with inner cavity Janus-Helmholtz transducer, acoustic radiation performance of outer cavity Janus-Helmholtz underwater acoustic transducer in the 0 degrees direction has been significantly improved.

Acoustic transfer function of cavity and its application to rapid evaluation of sound field at low frequency band

A new method to obtain numerical solution of Acoustic Transfer Function (ATF) by BEM is presented. For a simply supported panel backed by a rectangular cavity at low frequency band (0-200 Hz), the frequency property of ATF is analyzed. The relation between the accuracy of the rapid evaluation of sound field and the discretization schemes of the vibrational panel is discussed. The result shows that the method to obtain ATF and the rapid evaluation of sound field using the ATF is suitable to low frequency band. If an appropriate discretization scheme is choosed based on the frequency involved and the effort to obtain ATF, the accuracy of the rapid evaluation of sound field is acceptable.

Whole-blood sorting,enrichment and in situ immunolabeling of cellular subsets using acoustic microstreaming

Analyzing undiluted whole human blood is a challenge due to its complex composition of hematopoietic cellular populations,nucleic acids,metabolites,and proteins.We present a novel multi-functional microfluidic acoustic streaming platform that enables sorting,enrichment and in situ identification of cellular subsets from whole blood.This single device platform,based on lateral cavity acoustic transducers(LCAT),enables(1)the sorting of undiluted donor whole blood into its cellular subsets(platelets,RBCs,and WBCs),(2)the enrichment and retrieval of breast cancer cells(MCF-7)spiked in donor whole blood at rare cell relevant concentrations(10 mL^(−1)),and(3)on-chip immunofluorescent labeling for the detection of specific target cellular populations by their known marker expression patterns.Our approach thus demonstrates a compact system that integrates upstream sample processing with downstream separation/enrichment,to carry out multi-parametric cell analysis for blood-based diagnosis and liquid biopsy blood sampling.

On acoustic performance for viscoelastic coating containing axisymmetric cavities using the multiple scattering method

A semi-analytical/numerical model based on the multiple scattering （MS） method has been established for analyzing the effect of acoustic performance on main energy attenua- tion mechanism in viscoelastic coating containing axisymmetric cavities. The basic functions of stress and displacement of the axisymmetric cavity surface are derived in the system of spheri- cal coordinates. The transition matrix between the incident wave and the scattering wave are obtained by the numerical integral of the basic functions of the cavity surface. The reflection, transmission and absorption performance of viscoelastic materials containing periodic cavities are calculated using the MS method and the wave propagating theory of the multi-layered medium. The results indicate that low frequency energy is mainly attenuated through cavity resonance. The resonant properties are found to be very sensitive to the boundary conditions. The coupling of the double-cavity is capable of extending the absorption to even lower fre- quencies. The absorption performance of the viscoelastic coating in the high frequency range is independent of the backing material. Its energy attenuation depends mainly on acoustic properties of cavity scattering and mode conversion.