Physical Acoustics Research Articles

National Center for Physical Acoustics Aeroacoustics Group

The Aeroacoustics Group at the National Center for Physical Acoustics (NCPA) was formed in 1999 to open a new avenue of research at the center. Since its inception, the group has strived to study fundamental problems of flow-generated pressure fluctuations (both acoustic and hydrodynamic) and transition them to applied problems predominantly in the aerospace field. Over the years these problems have included vibrations in bodies traveling at supersonic speeds, jet noise associated with supersonic and subsonic exit conditions, and flow over open cavities to name a few. As part of these efforts, the group has added substantial unique infrastructure to the NCPA expanded the capabilities of the research done in house. The presentation will highlight key features of the problems, which have been studied by the group along with the key personnel.

Current research thrusts at NCPA

Over the 30 year history of the National Center for Physical Acoustics, the technologies have advanced and research has evolved; however, the mission has remained the same: to pursue solutions to practical problems using a fundamental physics approach, to educate the next generation of physical acousticians, and to serve as a translational bridge between basic research generated by our academic communities and the private sector. In this talk, I will discuss major research thrusts and accomplishments of NCPA in the last 5–8 years. Topical areas covered will be infrasound and long range propagation, aeroacoustics, structural health monitoring, physical ultrasound, and acoustics in porous media. I'll include some discussion of prominent scientists driving this research along with a few funny stories.

Before there was a National Center for Physical Acoustics: Memories of the first employee

New laboratories, like newborn babies, usually come into the world along with a mix of excitement, joy, anxiety, and pain. Most of these feelings were present in the Ole Miss physics department when I arrived on the campus in August of 1985. Over the next few years, I watched what started as an attempt to obtain a metal building for acoustics research, evolve into what is today the National Center for Physical Acoustics (NCPA). In this presentation, I will tell some stories about the birth and early days of the NCPA as seen by a newly arrived outsider. Some of the stories are funny and others are not. I hope to convey what it was like to know something important was happening even though no one, especially me, seemed to know exactly where things were headed.

Finite element models of crystallized white dwarf cores: A gateway to undergraduate physical acoustics and computational modeling of complex systems

In this work we present details of several finite element (FE) models of white dwarf stars with cores composed of layered crystalline carbon, oxygen and neon. The FE models, produced by undergraduate physics majors, are constructed using a commercially available software package Femap with NX Nastran. These models can be used to understand the effect of stellar composition and crystallization ratios on white dwarf behavior including vibrational modes, surface velocity and variation in luminosity. While the nature of these ultra-dense stellar remnants can appear quite exotic, the physical acoustic principles required to build and analyze the FE models are directly related to those commonly utilized by research acousticians. This gateway project was designed for undergraduate physics majors in order to illustrate this connection and to encourage interest in applied physical acoustics. The inherent interdisciplinary nature of the project also provides an opportunity for undergraduate physics majors to explore fields that are often considered disparate while improving their computational modeling skills.

Design of homework problems in physical acoustics

A variety of methods exist to help students master material in their acoustics courses. The method chosen depends a great deal on the course. In the graduate acoustics courses at UT Austin the methods include system identification and design projects in the course on acoustical transducers, measurements, and data analysis in the courses on architectural acoustics and ultrasonics, development of computer codes based on the sonar equation in the course on underwater acoustics, and a project usually requiring literature review in the course on nonlinear acoustics. Homework problems is the method of choice for the two-semester basic course on physical acoustics, because mastery of the fundamental principles of acoustics requires students to immerse themselves in the details specific to each particular topic. Learning basic acoustics is a lot like learning calculus: one learns by doing. This presentation discusses the philosophy behind creation of the homework problems that appear in the textbook Fundamentals of Physical Acoustics by Blackstock [Wiley 2000]. The problems do not require use of a computer. They do require judgment over plugging and chugging. The student must decide what section of a chapter applies to the problem assigned and also what approximations are permissible to simplify the work.

Nonlinear acoustic spectroscopy of carbonate rocks

The paper presents the results of experimental research into the nonlinear acoustic properties of carbonate rocks depending on saturation. The linear acoustic properties of the same sample depending on saturation were presented earlier in Physical Acoustics. The previously obtained data point to the isotropy of the material, which makes it possible to restrict analysis to only two vibration modes. Responses for finite deformations were measured for the longitudinal and shear modes of an isotropic sample, which made it possible to analyze the nonlinear properties of macroscopic deformations with a change in volume and pure displacement. A heretofore unknown feature of the response was revealed for finite deformation values; it is related to the occurrence of a jumplike transition from classical nonlinearity to a hysteresis type of nonlinearity. As well, the deformation amplitude corresponding to the transition depends on fluid saturation. We studied the slow relaxation that occurs after long-term excitation of a sample with a deformation amplitude on the order of 10−6. Data are presented on relaxation for deformation from pure displacement and deformation with a change in volume, which made it possible to isolate features related to the type of deformation and to compare the obtained data with the earlier published theoretical model. These data are compared with the results of other research groups.

Ed Carstensen, advisor and mentor to the shockwave lithotripsy program project group

In the 1980s shockwave lithotripsy emerged as a revolutionary advancement for the treatment of kidney stones. Initial studies with patients showed SWL to be highly effective. The technology was elegant, outcomes exceptionally positive and early tests suggested treatment was safe. As experience with SWL grew, limitations surfaced. A key finding was that SWs have the potential to induce significant trauma to the kidney. Our group convinced the NIH it was time to conduct a rigorous assessment to characterize the adverse effects of SWL and determine the mechanisms of SW action in stone breakage and tissue injury. The NIH Program Project Grant mechanism mandated we establish a panel of external advisors to help guide our work. We needed expertise in physical acoustics, cavitation and animal models of ultrasound exposure. We wanted a leading expert. We were extremely fortunate to land Ed Carstensen. Ed worked with us for nearly 15 years, well into our third renewal cycle. He was a brilliant scientist, a man ded...

Exploring the physical theory of diffraction for solutions of wedge fields in room-acoustic simulation

The need of developing accurate and cost-effective room-acoustic simulations has prompted recent investigations on edge diffractions with some progresses on solving multiple-order diffractions of finite wedges. This work explores an alternative approach based on the physical theory of diffraction [P. Ya. Ufimtsev, J. Acoust. Soc. Am. 120, 631-635 (2006)] which is well suited for solving acoustic scattering problems from reflecting objects for room-simulation purposes. Although the approaches based on the principle of geometrical acoustics (GA) are widely applied, they are less suitable for geometrical shadow boundaries. The physical theory of diffraction still relies on both geometrical and physical principles, yet emphasizes the physical one. One of the important features of this physical acoustics (PA) approach is the ability to calculate the sound field more accurately in shadow boundaries. To this end, exact and asymptotic solutions of wedge fields are discussed for secondary edge sources induced by the incident wave. This paper will discuss implemented results of several canonical cases with emphasis on Neumann boundary condition.

The Physical Acoustics Research Program at the University of Louisiana at Lafayette

The Department of Physics at UL Lafayette has a strong history of acoustics research. Recently, the program has expanded considerably as a result of renewed interest in acoustics-related research. Tied into the current rethinking of the Department's multiple physics tracks, the Physical Acoustics Research Program offers ample opportunities for students—both undergraduate and graduate—to be involved in wide-spectrum research in acoustics. This program, unique in Louisiana, involves acoustic sensing of alien environments, atmospheric and underwater acoustics, ultrasonics in the solid state, ultrasonic materials characterization and structural health monitoring, seismology and geodynamics. In parallel to research projects, the faculty offer a variety of acoustics-related courses on topics such as Matlab- and Python-based computational acoustics, solid state acoustics, experimental techniques in acoustics, room acoustics, as well as machine learning techniques for wave propagation.

NCPAprop—A software package for infrasound propagation modeling

Developed by the infrasound group at the National Center of Physical Acoustics, University of Mississippi, and a few collaborators, NCPAprop is an open source software package aiming at providing a comprehensive set of tested and validated numerical models for simulating the long range propagation of infrasonic signals through the earth's atmosphere. The algorithms implemented in NCPAprop are designed for frequencies large enough that the effects of buoyancy can be neglected and small enough that propagation to ranges of hundreds to thousands of kilometers is possible without significant signal attenuation. Nominally, NCPAprop can, without modification, be used to efficiently model narrowband propagation from 0.1 to 10 Hz and broadband propagation from 0.05 Hz to 2 or 3 Hz. NCPAprop provides both geometrical acoustic and full wave models which will be presented. The geometrical acoustics part consists of 2-d and 3-d ray tracing programs as well as a non-linear ray theory model. The full wave models consist of a suite of normal mode models of increasing complexity and a Parabolic Equation (PE) model.

Reciprocity calibration for infrasound sensors

Frequency response is a key parameter in understanding the impact of a transducer on a measurement. A single volts-per-pascal value is often cited as an acoustic transducer’s response; however, the magnitude and phase of this ratio over the entire frequency range of interest is required to understand the effects of that transducer on input waveforms. While this ratio can be determined by comparison to a reference transducer, any reference must itself be calibrated in some fashion. The National Center for Physical Acoustics has built two calibration chambers designed for evaluation of infrasound microbarometers. The large interior volume (about 1.5 cubic meters) allows simultaneous testing of several microbarometers and reference transducers. These chambers are also equipped with two drivers—10-in. subwoofers—so that two-tone linearity testing can be done. The incorporation of two drivers opens the possibility for implementing reciprocity calibration, a well-established primary calibration methodology. This paper describes development, evaluation, and uncertainties of a reciprocity-based calibration procedure designed expressly for measuring the complex frequency response of infrasound sensors in the 0.005 to 10 Hz frequency range.

Constellation: A hybrid active accoustic system

Constellation is a hybrid active acoustic system that has been used in rooms ranging in size from a virtual reality cave to a sports arena. Constellation has been shown to control both the effective absorption of a room as well as the effective cubic volume. This paper will review how early reflections, effective absorption, and effective cubic volume have been controlled in rooms of various sizes. Recently, there has been a trend of larger classical ensembles performing in smaller venues. If the strength of the room is held constant, but the cubic volume is cut in half, the reverberation time is also cut in half. If a room has exclusively physical acoustics, it is impossible to replicate both the strength and reverberation time of a symphony hall in a space that is considerably smaller (such as a rehearsal room). A special emphasis will be made on how Constellation is uniquely suited to address this challenge.

46th Winter School on Wave and Quantum Acoustics XLVth Jubilee Winter School on Environmental Acoustics and Vibroacoustics Szczyrk, Poland, February 27 – March 2, 2017

46th Winter School on Wave and Quantum Acoustics constitutes a platform for sharing the results and achievements obtained in different branches of physical acoustics. During the Conference Workshop on Acoustoelectronics and Workshop on Molecular Acoustics, Relaxation and Calorimetric Methods will be held. XLVth Jubilee Winter School on Environmental Acoustics and Vibroacoustics is the forum for all environmental and vibroacoustics fields. Particularly it concerns traffic noise, vibroacoustics of machines, room acoustics, building acoustics, noise protection and similar problems. During the Conference in association with SVANTEK there will be organised seminars on “Measurement of noise and vibration at the workplace”, “Enivironmental noise monitoring” combined with measurement workshops.

Generating arbitrary ultrasound fields with tailored optoacoustic surface profiles

Acoustic fields with multiple foci have many applications in physical acoustics ranging from particle manipulation to neural modulation. However, the generation of multiple foci at arbitrary locations in three-dimensional is challenging using conventional transducer technology. In this work, the optical generation of acoustic fields focused at multiple points using a single optical pulse is demonstrated. This is achieved using optically absorbing surface profiles designed to generate specific, user-defined, wavefields. An optimisation approach for the design of these tailored surface profiles is developed. This searches for a smoothly varying surface that will generate a high peak pressure at a set of target focal points. The designed surface profiles are then realised via a combination of additive manufacturing and absorber deposition techniques. Acoustic field measurements from a sample designed to generate the numeral “7” are used to demonstrate the design method.

15th Anglo-French Physical Acoustics Conference (AFPAC 2016)

The 15th Anglo-French Physical Acoustics Conference (AFPAC) was held at Selsdon Park Hotel, near London, United Kingdom, on 13-15 January 2016. The venue was an excellent location to exchange ideas, regardless whether this took place in the conference room, over lunch, at the drinks reception, or in the bar after the conference dinner. A total of 65 papers were presented at the conference. There were over 80 delegates from institutions covering five countries.On the first day of AFPAC, the Institute of Physics joined forces with the National Physical Laboratory (UK) to host a special session on cavitation. The Cavitation User Forum, a bi-annual event specifically dedicated to applications of high power ultrasound, brought together experts from academia and from the cleaning, processing and medical industries. This session was kicked off with an invited talk by Dr David Fernandez Rivas (University of Twente, The Netherlands), on the reproducibility of sonochemistry and ultrasonic cleaning.The Cavitation User Forum was followed by a special session on biomedical ultrasound, co-sponsored by the Medical Physics Group of the Institute of Physics, which featured a keynote talk by Prof Robin Cleveland (University of Oxford) on ultrasonic surgery. The session included talks on acoustic microscopy of live cells, histotripsy, phase-insensitive ultrasound computed tomography for the diagnosis of breast cancer, high-intensity focused ultrasound and the biomedical applications of solitary wave impulses generated by granular chainsThe second day featured an invited presentation by Prof Tim Leighton (University of Southampton, UK) on the acoustic bubble, which discussed ocean, cetacean and extra-terrestrial acoustics, and cold water cleaning. Prof Christ Glorieux (KU Leuven, Belgium) discussed the applications of photothermal and photoacoustic methods using different spatiotemporal excitation patterns. A broad range of physical acoustics topics was reviewed that day. Work was presented on phononic crystals, high resolution imaging of in-depth rough interfaces, shear wave reconversion in nano-fluids and the prediction of radiation by finite-sized sources in semi-infinite isotropic plates. The field of non-destructive evaluation was well represented, with a presence from institutions such as Imperial College London, University of Nottingham and Université de Montpellier.During the Conference Dinner, the 2015 Bob Chivers prize was awarded to Dr Bo Lan for his paper entitled “Experimental and computational studies of ultrasound wave propagation in hexagonal close-packed polycrystals for texture detection”.On the final day of the conference, Prof Olivier Dazel (Université du Maine, Le Mans, France) gave an invited talk discussing the past present and future of the modelling of sound absorbing materials.The UK organising committee was particularly happy to welcome the many French contributors that travelled to Selsdon Park and would like to thank Alain Lhémery and the Société Française d’Acoustique (SFA) for publicising the event in France. We are happy to announce that many of the presented papers will be published in the conference proceedings in Journal of Physics: Conference Series. We would also like to draw the reader’s attention to the upcoming 16th AFPAC conference that is scheduled to take place on 23-25 of January 2017 at the Laboratoire de Mécanique et d’Acoustique, Marseille, France.Pierre Gélat (UCL, United Kingdom), Theodosia Stratoudaki (University of Nottingham, United Kingdom), Rachel Edwards (University of Warwick, United Kingdom), Robert Malkin (University of Bristol), Nader Saffari (UCL, United Kingdom) and Alain Lhémery (CEA, France)

Thévenin acoustics.

Thévenin's theorem is commonly used in the analysis of acoustic transducers to provide a simplified representation of a transducer or its environment. The method may be extended to the analyses of other acoustic systems, without limitation to systems that have been reduced to analogous circuit models, and is particularly convenient in the analysis of acoustic scattering when the scattering object is mobile. In this paper, the method is illustrated through an alternative derivation of the well-known "mass law" for transmission through a partition, and is also applied to the case of acoustic scattering from a rigid, mobile cylinder of arbitrary size in an ideal plane progressive wave. Differences between the conventional solution approach for such problems and the Thévenin-inspired method are discussed, along with the potential benefits of taking such an approach for the simplification of other problems in physical acoustics.

Teaching Mathematica® based computer computations for support of laboratory experiments, special projects, and research for undergraduates taking acoustics and for mentorship students

Undergraduate senior level physics majors taking Acoustics and oceanography majors taking Underwater Acoustics and Sonar learn how to use Mathematica® for doing standard laboratory experiments, special projects, solving homework problems requiring detailed computations or graphics. Students in electrical engineering, economics, mechanical engineering and ocean engineering (along with physics majors) have enrolled in a one credit course—Mathematica® 10 for Scientists and Techies. The feedback from students using a computer language in their course work for the first time is very encouraging and the teaching experience quite rewarding. High school mentorships volunteering to do research after school use Mathematica® for doing projects in the Physical Acoustics Laboratory. Some undergraduate lab projects involve Fourier analysis, measuring sound speed vs. temperature in water, and plotting theoretical and experimental Bessel mode shapes (or cosine shapes) for standing wave resonance in a cylindrical cavity. Here, a long slender tube mounted on the microphone probe translates along the radial or axial directions. Students enjoy generating their own data on a spectrum analyzer, transferring files to Mathematica® and plotting tuning curves vs. frequency in Helmholtz resonators. One student got involved in nonlinear drum vibration while another became interested in synthetic aperture imaging, for senior research projects.

Flow-Control Optimization Maximizes Accuracy of Multiphase-Flow Rate Allocation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173873, “Flow-Control Optimization To Maximize the Accuracy of Multiphase-Flow Rate Allocation,” by Reza Malakooti, Khafiz Muradov, and David Davies, Heriot-Watt University, and Alexander Kuznetsov, Weatherford, prepared for the 2015 SPE Bergen One Day Seminar, Bergen, Norway, 22 April. The paper has not been peer reviewed. The value added by intelligent wells (I-wells) derives from real-time reservoir and production-performance monitoring together with zonal downhole flow control. Unfortunately, downhole sensors that directly measure the flow rates and phase cuts required for optimal control of the well’s producing zones are not typically installed. This paper describes an “active” monitoring technique that uses a direct search method to optimize the sequence of interval-control-valve (ICV) positions during a routine multirate test in an I-well. Introduction I-well completions include both downhole flow-control tools and monitoring sensors. Reservoir inflow is controlled by means of passive devices [inflow- control devices (ICDs)], active valves (ICVs), and self-adjusting devices ( autonomous ICDs and autonomous ICVs). Reservoir and well-performance properties should be monitored regularly to support flow- control decisions efficiently. Various physical quantities, including temperature, pressure, flow rate, acoustics, strain, and seismic, are currently measured by electronic, radioactive, and fiber-optic sensors to assist the multiphase-flow rate allocation in I-wells. Producing from only a single well or zone during a test is a common practice. This delivers a single flow-rate value measured at a particular time. However, this approach is inefficient, resulting in lost production and possible difficulties when trying to restart the closed-in wells or zones. A costly production-logging well intervention is a possible alternative; it does provide an inflow rate and a phase-cut profile, but only at a specific time without the possibility of delivering the current phase cut and production rate continuously. The alternative is to use (continuous) passive indirect measurements. Such soft-sensing techniques are used widely in (surface) facilities and process plants where extensive, complex networks of sensors can be implemented relatively easily. They are now being introduced for reservoir and well applications. A multiphase soft sensor consists of (1) an estimation technique, (2) a multiphase-flow model, and (3) the measurements. The multiphase-flow model relates the measurements to the parameters required for the estimation of downhole flow rates. The estimation technique is used to compute these parameters by minimization of the mismatch between measured information and predicted values. Published soft sensors have used both stochastically and deterministically based optimization methods as the estimation technique. The complete paper provides a review of recent research and developments in this field. Soft-sensing techniques are subjected to multiphase-flow-model errors and measurement uncertainties. The latter refers to variance of the values attributed to a measured quantity. For this reason, a new approach is required to overcome the limitation of the passive soft- sensing techniques used to allocate downhole flow rates. To accomplish this goal, an active multiphase-flow-rate soft-sensing method has been developed to design an optimum series of flow tests. The soft sensor obtains the most accurate estimate of the zonal properties by use of the deformed-configuration (DC) method to optimize the flow-test conditions (the ICV flow area in multizone I-wells or the wellhead-choke position for multiple conventional wells). To the authors’ knowledge, this work is the first publication to demonstrate the applicability of the DC optimization method in well soft-sensing problems.

Acoustical Society of America Helmholtz-Rayleigh Interdisciplinary Silver Medal in Physical Acoustics, Biomedical Acoustics, and Engineering Acoustics: Armen Sarvazyan

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

Introduction to the Technical Committee on Physical Acoustics

The Technical Committee on Physical Acoustics (TCPA) of the Acoustical Society of America (ASA) includes scientists and engineers with an interest in the underlying physics of acoustical phenomenon. What unifies the members of TCPA is the approach to answering a particular question. The types of phenomena of interest to the physical acoustics community are fundamental acoustic wave propagation, including transmission, reflection, refraction, interference, diffraction, scattering, absorption, and dispersion of sound covering the entire frequency range from infrasound to ultrasound. There is also interest in the use of acoustics to study physical properties of matter, and to produce changes in these properties. TCPA currently has about 575 members with a primary interest in physical acoustics with 75–125 typically attending open TCPA meetings.