3D Acoustic Field Research Articles

Morphological diversity in the sensory system of phyllostomid bats: Implications for acoustic and dietary ecology

Abstract Sensory systems perform fitness‐relevant functions, and specialized sensory structures allow organisms to accomplish challenging tasks. However, broad comparative analyses of sensory morphologies and their performance are lacking for diverse mammalian radiations. Neotropical leaf‐nosed bats (Phyllostomidae) are one of the most ecologically diverse mammal groups; including a wide range of diets and foraging behaviours, and extreme morphological variation in external sensory structures used in echolocation (nose leaf and pinnae). We coupled 3D geometric morphometrics and acoustic field recordings under a phylogenetic framework to investigate the mechanisms underlying the diversification of external sensory morphologies in phyllostomids, and explored the potential implications of sensory morphological diversity to functional outputs and dietary ecology. We found that the nose leaf consists of two evolutionary modules—spear and horseshoe—suggesting that modularity enabled morphological and functional diversification of this structure. We found a significant association between some aspects of nose leaf shape and maximum frequency and bandwidth of echolocation calls, but not between pinnae shape and echolocation call parameters. This may be explained by the use of multiple sensory modes across phyllostomids and plasticity of some echolocation call parameters. Species with different diets significantly differed in nose leaf shape, specifically in spear breadth, presence of a midrib, and cupping and anterior rotation of the horseshoe. This may relate to different levels of prey type specificity within each diet. Pinnae shape significantly differed between species that consume non‐mobile, non‐evasive prey (broad rounded, cupped pinnae) and mobile, evasive prey (flattened pinnae with a sharp tapering apex). This may reflect the use of different sound cues to detect prey. Our results give insight into the morphological evolution of external sensory structures in bats, and highlight new links between morphological diversity and ecology. A free Plain Language Summary can be found within the Supporting Information of this article.

Blood-brain barrier disruption in humans using an implantable ultrasound device: quantification with MR images and correlation with local acoustic pressure.

One of the goals in this study was to set up a semiautomatic method to estimate blood-brain barrier disruption obtained in patients with glioblastoma by using an implantable, unfocused, ultrasound device. Another goal was to correlate the probability of significant ultrasound-induced signal enhancement (SUISE) with local acoustic pressure in the brain. Gd-enhanced MR images acquired before and after ultrasound treatments were analyzed prospectively. The image sets were segmented, normalized, and coregistered to evaluate contrast enhancement. The volume of SUISE was calculated with voxels labeled as gray or white matter, in a cylindrical region of interest, and with enhancement above a given threshold. To validate the method, the resulting volumes of SUISE were compared to qualitative grades previously assigned by 3 clinicians for 40 ultrasound treatments in 15 patients. A parametric study was performed to optimize the algorithm prediction of the qualitative grades. The 3D acoustic field in the brain was estimated from measurements in water combined with simulations accounting for ultrasound attenuation in brain and overlaid on each MR image to correlate local acoustic pressure with the probability of SUISE (defined as enhancement > 10%). The algorithm predicted grade 2 or 3 and grade 3 openings with areas under the receiver operating characteristic curve of 0.831 and 0.995, respectively. The probability of SUISE was correlated with local acoustic pressure (R2 = 0.98) and was 3.33 times higher for gray matter than for white matter. An algorithm for evaluating blood-brain barrier disruption was validated and can be used for future clinical trials to further understand and quantify this technique in humans.Clinical trial registration no.: NCT02253212 (clinicaltrials.gov).

Controlled removal of micro/nanoscale particles in submillimeter-diameter area on a substrate.

In this paper, a removal method of micro/nanoscale particles in a submillimeter-diameter area at the interface between an aqueous suspension droplet and silicon substrate surface around a selectable point is proposed and demonstrated. It employs the acoustic streaming generated by an ultrasonically vibrating micro manipulating probe (MMP). The operating frequency of the device is 124.5 kHz, at which the micro manipulating probe oscillates approximately linearly. The experiments show that microscale particles with a diameter of 3-5 μm and nanoscale particles with a diameter of 300-500 nm in submillimeter-diameter areas can be removed in about 1.5 min. The principle of the cleaning method is analyzed by measuring the device's vibration mode and computing the 3D acoustic streaming field around the MMP. The diameter of cleaned area versus sonication time is clarified by experiments as well as the stable diameter of cleaned area versus vibration velocity. The dependency of the acoustic streaming field on the working parameters, which include the distance between the MMP's tip and substrate, the angle between the MMP and substrate, and the ratio of the normal vibration components of the MMP, is also investigated by the FEM (finite element method) computation. To the best of our knowledge, this is the first time to report a method for the removal of micro/nanoscale particles in a submillimeter range around a selectable point.

3D Acoustic Field Intensity Probe Design and Measurements

Abstract The aim of this paper is two-fold. First, some basic notions on acoustic field intensity and its measurement are shortly recalled. Then, the equipment and the measurement procedure used in the sound intensity in the performed research study are described. The second goal is to present details of the design of the engineered 3D intensity probe, as well as the algorithms developed and applied for that purpose. Results of the intensity probe measurements along with the calibration procedure are then contained and discussed. Comparison between the engineered and the reference commercial probe confirms that the designed construction is applicable to the sound field intensity measurements with a sufficient effectiveness.

Acoustic field measurement of high-intensity ultrasound source system using acoustic waveguide for calibration of hydrophone

In recent years, high-intensity ultrasound equipments have been used. It is expected that nonlinear calibration and evaluation will be needed more often. It is necessary to develop a high-intensity ultrasound source that transmit a plane wave in far-field for calibration of hydrophone in order to evaluate high intensity acoustic field. We proposed an ultrasound source system using a cylindrical type acoustic waveguide and a concave type piezoelectric transducer. The focused ultrasound wave is emitted from the concave type transducer, propagated through the acoustic waveguide, and the output from that forms high-intensity acoustic beam. We simulated the output acoustic pressure of the proposed source system using axisymmetric 3D acoustic field simulation based finite element method, compared with that of a flat disk type transducer with the same aperture size as the acoustic waveguide, and the simulated data showed the acoustic pressure of our proposed system was higher than that of the flat disk type transducer with the same main beam width. We fabricated the experimental source system using the concave type piezoelectric transducer and the acoustic waveguide using closed cell sponge, and measured acoustic pressure distribution. The obtained results were nearly coincident with the simulated data

Effects of seabed curvature on the scattered acoustic field

Knowledge of the acoustic properties of the sea bottom provides valuable input into the development and performance of information processing algorithms designed to detect and identify, e.g., man-made objects near to, or embedded in, the seabed. This information is also useful for improving modeling and simulation results in reverberation-limited environments. A critical challenge in this area is in allowing for range dependent bathymetry as it can affect the propagating acoustic field in ways that are difficult to predict. Typical approaches to modeling variable bathymetry assume either piecewise flat or tilted (linear) geometry; however, this only serves as a discrete approximation to reality. This study investigates the effects of mild curvature on the 3D acoustic field in frequency and angle space via finite difference time domain simulations. We present results and discuss the implications on forward modeling of the acoustic interaction with the seabed. [Work supported by the Strategic Environmental Research and Development Program (SERDP).]

Analyses of acoustic streaming field in the probe-liquid-substrate system for nanotrapping

The probe-liquid-substrate system, in which a micro-manipulation probe (MMP) is inserted into a liquid film of nanosuspension on a substrate, is very useful in nanomanipulations. With the MMP’s vibration, a three-dimensional (3D) acoustic streaming field around the MMP is generated, which has been used to trap, transfer and rotate nanoentities in the liquid film. However, research on the details of the 3D acoustic streaming field in the probe-liquid-substrate system has been scarce. In this work, the 3D acoustic streaming field in a probe-liquid-substrate system for the contact-type trapping of individual nanowires is numerically investigated by the finite element method. The computational results show that the MMP root’s elliptical vibration can generate an acoustic streaming field capable of trapping a single nanowire in the contact mode. This conclusion can well explain the experimental phenomena that the MMP can trap a single nanowire at some frequencies and cannot at others. The computational results clarify the effect of the distance between the MMP and substrate, the MMP’s radius and length, and the water film’s thickness on the acoustic streaming field.

Exact solution of three-dimensional acoustic field in a wedge with perfectly reflecting boundaries

An exact approach is presented to compute the three-dimensional (3D) acoustic field in a homogeneous wedge-shaped ocean with perfectly reflecting boundaries. This approach applies the Fourier synthesis technique, which reduces a 3D point-source ideal wedge problem into a sequence of two-dimensional (2D) line-source ideal wedge problems, whose analytical solution is well established. A comparison of numerical efficiency is provided between this solution and the solution proposed by Buckingham, which is obtained by a sequence of integral transforms. The details of numerical implementation of these two solutions are also given. To validate the present approach and at the same time compare numerical efficiency between this approach and Buckingham’s analytical solution, two numerical examples are considered. One is the Acoustical Society of America (ASA) benchmark wedge problem and the other is a wide-angle wedge problem. Numerical results indicate that the present approach is efficient and capable of providing accurate 3D acoustic field results for arbitrary receiver locations, and hence can serve as a benchmark model for sound propagation in a homogeneous wedge-shaped ocean.

Analytical and numerical prediction of harmonic sound power in the inlet of aero-engines with emphasis on transonic rotation speeds

Tone noise radiated through the inlet of a turbofan is mainly due to rotor-stator interactions at subsonic regimes (approach flight), and to the shock waves attached to each blade at supersonic helical tip speeds (takeoff). The axial compressor of a helicopter turboshaft engine is transonic as well and can be studied like turbofans at takeoff. The objective of the paper is to predict the sound power at the inlet radiating into the free field, with a focus on transonic conditions because sound levels are much higher. Direct numerical computation of tone acoustic power is based on a RANS (Reynolds averaged Navier–Stokes) solver followed by an integration of acoustic intensity over specified inlet cross-sections, derived from Cantrell and Hart equations (valid in irrotational flows). In transonic regimes, sound power decreases along the intake because of nonlinear propagation, which must be discriminated from numerical dissipation. This is one of the reasons why an analytical approach is also suggested. It is based on three steps: (i) appraisal of the initial pressure jump of the shock waves; (ii) 2D nonlinear propagation model of Morfey and Fisher; (iii) calculation of the sound power of the 3D ducted acoustic field. In this model, all the blades are assumed to be identical such that only the blade passing frequency and its harmonics are predicted (like in the present numerical simulations). However, transfer from blade passing frequency to multiple pure tones can be evaluated in a fourth step through a statistical analysis of irregularities between blades. Interest of the analytical method is to provide a good estimate of nonlinear acoustic propagation in the upstream duct while being easy and fast to compute. The various methods are applied to two turbofan models, respectively in approach (subsonic) and takeoff (transonic) conditions, and to a Turbomeca turboshaft engine (transonic case). The analytical method in transonic appears to be quite reliable by comparison with the numerical solution and with available experimental data.

2B23 超音波2次元アレイを用いた微小気泡の局所的動態制御のための時間変化を伴う音場の設計と形成(OS7-1:次世代超音波診断・治療技術(1))

2B23 超音波2次元アレイを用いた微小気泡の局所的動態制御のための時間変化を伴う音場の設計と形成(OS7-1:次世代超音波診断・治療技術(1))

An Experimental Methodology for the Reconstruction of Three-Dimensional Acoustic Pressure Fields in Ducts

The claim for low emission engines, imposed by strict environmental legislation, has prompted the aeronautical industry to reduce both noise emission and pollution by using lean combustion technology. These engines are often affected by acoustic instabilities that can compromise their correct functioning. A 3D acoustic wave field investigation is increasingly relevant for a correct design and comprehension of this kind of phenomena. Numerical codes are widely used for this type of analysis but an experimental validation is still required due to the complexity of the real phenomena involved in acoustic generation and propagation. While the wall acoustic pressure can be easily measured, very few examples of radial measurement for a 3D analysis can be found in research on this subject. This paper presents an example of a radial measurement of a 3D acoustic pressure field by means of a waveguide probe based on a 1/4" pressure microphone. In particular, several probe geometries were designed and calibrated on a specialized test rig. In order to verify the adopted methodology, the acoustic 3D pressure fields of two simplified geometries were measured and compared with those from a theoretical model describing the actual conditions of the test rig.

A New Modified SVD Method Applied in 3D Acoustic Temperature Field Reconstruction

In order to solve the ill-posed problem in 3D acoustic temperature field reconstruction, the paper proposed a new modified singular value decomposition (SVD) method.According to their reliability ,singular values were divided into three parts and got various degree of modification respectively. To verify the performance of the new algorithm based on the modified SVD method,two model temperature fields were reconstructed when the signal-to-noise ratio (SNR) of sound flight-time data was 50dB , 40dB and 30dB respectively.And the results were compared with those based on routine Truncated singular value decomposition (TSVD) and Tikhonov methods. Simulation results show that the new algorithm has higher precision, better anti-noise ability than the routine methods and it is more suitable for the complex temperature fields reconstruction, thus it is expected to be used for temperature field reconstruction on-line.

Optical Phase Contrast Mapping of Highly Focused Ultrasonic Fields

The most common method of measuring an ultrasonic pressure field is a hydrophone scan. However, this method has a long scanning time and disturbs the acoustic field. In this study, we used an optical phase contrast method for the measurement. Because this method uses light, fast and noninvasive measurement can be performed. The projections of an ultrasonic pressure field were obtained with a charge-coupled device (CCD) camera, and the three-dimensional (3D) acoustic pressure field was reconstructed using a computed tomography (CT) algorithm from these projections. The result was compared with that of hydrophone measurement and demonstrated the successful reconstruction of a focal ultrasonic pressure field.

Comparison of two-dimensional axial-symmetric and two-in-one-half dimensional Green's function methods for three-dimensional shallow water acoustic propagation using finite element methods

In shallow water acoustic propagation, performing a fully three-dimensional finite element model is currently unfeasible due to difficulty in implementation and limits in computational power. Therefore, alternative representations of the 3D acoustic field are sought. Two promising methods to represent the 3D field are a locally invariant, 2.5D Green’s Function kernel, and a 2D axial-symmetric reduction of the 3D Helmholtz equation. When a spherical source is used, azimuthal symmetry of the acoustic propagation is assumed, and these two methods can be compared in 2D planes of the 3D field. Because the 2.5D method takes more computational time than the axial-symmetric method, the accuracy of the pressure field are compared to see if the axial-symmetric method can be used in place of the 2.5D method. First, the two methods are compared for a flat ocean surface with stratified media. Then, a wedge-shaped ocean surface is considered, and the two methods are compared with 2D PE solutions. These comparisons will show if the axial-symmetric method produces similar results to the 2.5D method, and if so, under which geometrical and physical situations the axial-symmetric method can be used in place of the 2.5D method. [Work sponsored by the Office of Naval Research, Ocean Acoustics.]

On the use of tailored functional bases for space launcher noise sources localization and reconstruction

A source localization and inverse reconstruction methodology is applied to analyze wall pressure signals measured on the surface of a space launcher mock-up. The methodology is based on the use of elementary acoustic solutions tailored to the space launcher geometry as functional basis. Two classes of functional bases are considered: plane waves impinging on the surface of an infinite cylinder computed analytically through a literature formula, and plane waves impinging on the real space launcher computed numerically through a FEM computational acoustic technique. In both cases, the 3D acoustic field resulting from the impingement of an arbitrarily oriented plane wave is obtained by a truncated series summation of elementary axial-symmetric solutions. These two classes of functional bases are proven to provide consistent results in the addressed frequency range. However, although the analytical basis enables a faster localization of the noise sources that take place during the rocket firing, the numerical basis is expected to enable, at an acceptable computational cost, a more reliable reconstruction of the acoustic loads on the space launcher surface in a higher frequency range. The proposed FEM-based beam-forming and source reconstruction technique is therefore a useful tool for the vibro-acoustic design of future launch vehicles.

Parallel Finite Difference Modeling of Acoustic Fields in Nonaxisymmetric Cased Hole

AbstractUsing finite difference time domain (FDTD) method with nonsplitting perfectly matched layer absorbing boundary condition, a parallel computation scheme based on Message Passing Interface on computer‐based cluster, is proposed to simulate high frequency (100 kHz) 3D transient acoustic field of Segmented Bond Tool logging in nonaxisymmetric cased hole. Average parameters of difference equations on the internal interfaces are proposed to improve the computational stability. This method is verified by the good agreement of the simulated waveforms with those obtained from the real‐axis integration method for axisymmetric cased hole. The waveforms of 8‐sector SBT logging in nonaxisymmetric cased hole with cement groove of various size and azimuth are simulated using the parallel FD algorithm, and the amplitude characteristics of casing wave versus included angle between cement groove and transducer are studied. New wave phenomena in nonaxisymmetric cased hole are presented. An idea to determine the size and azimuth of the cement groove is proposed.

A Spectral Coupled-Mode Formulation for Sound Propagation around Axisymmetric Seamounts

A spectral coupled-mode solution of the three-dimensional (3D) acoustic field generated by a point source in the presence of an axisymmetric seamount is developed. Based on the same theoretical foundation as the formulation presented by Taroudakis [J. Comput. Acoust. 4 (1996) 101], the present approach combines a spectral decomposition in azimuth with a coupled-mode theory for two-way range-dependent propagation. However, the earlier formulations are severely limited in terms of frequency, size and geometry of the seamount, the seabed composition, and the distance between the source and the seamount, and are therefore severely limited in regard to realistic seamount problems. Without changing the fundamental theoretical foundation, the present approach applies a number of modifications to the formulation, leading to orders of magnitude improvement in numerical efficiency for realistic problems. Therefore, realistic propagation and scattering scenarios can be modeled, including effects of seamount roughness and realistic sedimentary structure.

Scaled model experiment of long-range across-slope pulse propagation in a penetrable wedge

In this paper, laboratory scale measurements of long-range across-slope propagation of broadband pulses in a shallow-water wedge-shaped environment with a sandy bottom are reported. The scaled model was designed to study the three-dimensional (3D) acoustic field in the presence of only a few propagating modes. The recorded time series exhibit prominent 3D effects such as mode shadow zones and multiple mode arrivals. Inspection of the spectral content of the time signals gives evidence of intra-mode interference and frequency dependence of the mode cut-off range in the across-slope direction.

Fricative synthesis investigations using the transmission line matrix method

We investigate the potential of properly applying the Transmission Line Matrix method to simulate the 3D acoustic field in the vocal tract especially for the synthesis of fricatives. For fricatives, we are mainly interested in the higher end of the spectrum where the planar wave propagation assumption that is accepted in the one‐dimensional simulation cannot provide accurate results. This is the main reason why we explore 3D acoustic field simulation. Proper incorporation of noise sources is considered to account for frication. Their placement and acoustic properties are investigated. Motivated by measurements of the airflow during fricative production, we also explore the influence of mean flow to acoustics in the tract. Sound propagation in moving medium is considered for this purpose. The applied vocal tract geometry is determined from 3D MRI images. We present computational considerations for the analyzed framework in parallel to potential benefits compared to the one‐dimensional vocal tract simulation.

Effects of solitons on acoustic energy flow in three dimensions

The impact of a train of nonlinear solitons on the propagation of acoustic energy in shallow water is examined. The soliton perturbations are based on an analytic formulation that produces a train of five soliton waves. Each wave front is parallel and has infinite extent in the horizontal direction. The acoustic field is modeled using a three-dimensional (3D) split-step Fourier parabolic equation (SSF/PE) approach defined in Cartesian coordinates. The standard PE approximation is employed in both depth and cross-range directions. Both pressure and particle velocity fields are computed in a self-consistent manner, allowing a full description of the 3D acoustic intensity field which describes the flow of energy in the presence of the solitons. Individual, low-order modes are extracted from the propagating field so that the impact on specific modes may be examined. The analysis is performed at various frequencies and for various source-receiver geometries relative to the soliton train. Emphasis is placed on the focusing and defocusing of acoustic energy between the various soliton waves. The impact of such soliton perturbations on signal variability and bearing resolution at the receiver will be quantified. [Work supported by ONR 321OA.]