Mcneilcummings6202

This letter investigates an acoustic metamaterial exhibiting a unique sound pressure amplification mechanism for ultra-low frequency sound attenuation. see more The system is constructed by integrating a flexible panel into the side-branch duct of a Herschel-Quincke (HQ) tube. A new peak emerges in the Sound Transmission Loss (STL) at a frequency far lower than the frequencies of the HQ tube-induced STL peaks. It cannot, after careful comparisons, be attributed to any local resonances, including structural resonances of the flexible panel or air resonances inside the side-branch cavities. To explain the underlying physics, several numerical simulations are performed. The results reveal that analog to a mechanical inerter, a "push-pull" force is created by the sound pressure difference between the sub-cavities in which a pressure amplification mechanism is generated at the interface of the embedded panel. This force is large enough to activate an out-of-plane motion of the flexible panel, trapping the incident sound power in a circular flow around the duct-branch loop. The unique phenomenon is successfully reproduced in experiment, where the flexible panel is made of carbon fiber. The proposed acoustic metamaterial can be used as silencing components for ultra-low frequency noise control in duct.The three-dimensional acoustic intensimetry employing multiple probe-modules are implemented for estimating the source distance by calculating the nearest intersection points of the vectors. The probe spacing, source localization error, and source distance affect the estimation error. It is found that the intensity vectors indicating the source location diverge in some directions due to the geometric singularity. Numerical and experimental tests are conducted with three probe-modules configured as an equilateral triangle on a plane. The result reveals that the large error due to geometric singularity can be significantly reduced by only excluding the corresponding vectors that cause the divergence.A two-degrees-of-freedom nonlinear cochlear model [Sisto, Shera, Altoè, and Moleti (2019). J. Acoust. Soc. Am. 146, 1685-1695] correctly predicts that the reticular lamina response is nonlinear over a wide basal region. Numerical simulations of suppression tuning curves agree with a recent experiment [Dewey, Applegate, and Oghalai (2019). J. Neurosci. 39, 1805-1816], supporting the idea that the strong susceptibility of the reticular lamina response to suppression by high-frequency tones does not imply that the total traveling wave energy builds-up in correspondingly basal regions. This happens because the reticular lamina is the lightest element of a coupled-oscillators system, only indirectly coupled to the differential pressure.Burst wave lithotripsy (BWL) is a technology for comminuting urinary stones. A BWL transducer's requirements of high-pressure output, limited acoustic window, specific focal depth, and frequency to produce fragments of passable size constrain focal beamwidth. However, BWL is most effective with a beam wider than the stone. To produce a broad-beam, an iterative angular spectrum approach was used to calculate a phase screen that was realized with a rapid prototyped lens. The technique did not accurately replicate a target beam profile when an axisymmetric profile was chosen. Adding asymmetric weighting functions to the target profile achieved appropriate beamwidth. Lenses were designed to create a spherically focused narrow-beam (6 mm) and a broad-beam (11 mm) with a 350-kHz transducer and 84-mm focal depth. Both lenses were used to fragment artificial stones (11 mm long) in a water bath, and fragmentation rates were compared. The linearly simulated and measured broad beamwidths that were 12 mm and 11 mm, respectively, with a 2-mm-wide null at center. The broad-beam and the narrow-beam lenses fragmented 44 ± 9% and 16 ± 4% (p = 0.007, N = 3) of a stone by weight, respectively, in the same duration at the same peak negative pressure. The method broadened the focus and improved the BWL rate of fragmentation of large stones.A fully three-dimensional (3D) omnidirectional numerical coupled mode model of acoustic propagation is detailed. A combination of normal mode and finite element computational methods is applied to produce the numerical results. The technique is tested in a strongly range-dependent ocean environment modeled after the Hudson Canyon. Modeled sound from three source locations selected over different bathymetric depths is examined to determine capabilities and difficulties associated with varying numbers of propagating vertical modes across the horizontal domain, and variable amounts of mode coupling. Model results are compared to those from a unidirectional Cartesian 3D parabolic equation simulation, and from adiabatic (uncoupled) simulations to illustrate the capabilities of the techniques to study the influences of coupling, strong refraction, and reflection.A cellular stimulation device utilizing an AT-cut quartz coverslip mounted on an ultrasonic live imaging chamber is developed to investigate the effect of piezoelectric stimulation. Two types of chambers deliver ultrasound at intensities ranging from 1 to 20 mW/cm2 to mesenchymal stem cells (MSCs) seeded on the quartz coverslip. The quartz coverslip imposes additionally localized electric charges as it vibrates with the stimulation. The device was applied to explore whether piezoelectric stimulation can facilitate chondrogenesis of MSCs. The results suggest piezoelectric stimulation drove clustering of MSCs and consequently facilitated chondrogenesis of MSCs without the use of differentiation media.A vertical line array can be deployed in deep water below the critical depth, the depth where the sound speed equals the sound speed at the surface, to take advantage of the lower ambient noise level (compared with above the critical depth) for target detection. To differentiate a submerged source from a surface source, a Fourier transform based method [McCargar and Zurk, J. Acoust. Soc. Am. 133, EL320-325 (2013)] was proposed for a narrowband signal that exploits the depth-related harmonic (oscillation) feature of the beam power time series associated with the target arrival. In this paper, incoherent matched beam processing is used to estimate the target depth. Where the replica (calculated) beam intensity or amplitude time series best matches that of the data is used to estimate the source depth. This method is shown, based on simulated data, to provide a better depth resolution in general and better ability to estimate the depth of a very shallow source (say at 10 m) and can be used to complement the Fourier transform based method.