Physical Acoustics Research Articles

On the Applicability of Kramers–Kronig Dispersion Relations to Guided and Surface Waves

In unbounded media, the acoustic attenuation as function of frequency is related to the frequency-dependent sound velocity (dispersion) via Kramers–Kronig dispersion relations. These relations are fundamentally important for better understanding of the nature of attenuation and dispersion and as a tool in physical acoustics measurements, where they can be used for control purposes. However, physical acoustic measurements are frequently carried out not in unbounded media but in acoustic waveguides, e.g., inside liquid-filled pipes. Surface acoustic waves are also often used for physical acoustics measurements. In the present work, the applicability of Kramers–Kronig relations to guided and surface waves is investigated using the approach based on the theory of functions of complex variables. It is demonstrated that Kramers–Kronig relations have limited applicability to guided and surface waves. In particular, they are not applicable to waves propagating in waveguides characterised by the possibility of wave energy leakage from the waveguides into the surrounding medium. For waveguides without leakages, e.g., those formed by rigid walls, Kramers–Kronig relations remain valid for both ideal and viscous liquids. Examples of numerical calculations of wave dispersion and attenuation using Kramers–Kronig relations, where applicable, are presented for unbounded media and for waveguides formed by two rigid walls.

Preface

20th Anglo-French Physical Acoustics Conference (AFPAC 2023) FOREWORD After two successive postponements due to a well-known malicious virus, the twentieth AFPAC was organized in France in Fréjus at the Villa Clythia, from January 24 to 27, 2023. To celebrate this twentieth edition by something special to be remembered, a picnic on the beach followed by a magnificent walk in the Estérel massif were organized, in very favorable weather (as shown by the picture below).This year again, the bet was successful! During the five half-days of conferences, 33 oral presentations including four invited talks were given, on very varied themes, all in the area of physical acoustics.The four high quality invited talks concerned subjects as varied as “The cochlea seen as an active metamaterial” by Fabrice Lemoult, “Guided wave testing of pipelines” by Mike Lowe, “Miniature ultrasonic surgical devices for integration with surgical robots” by Margaret Lucas and “Ultrasound backscattering by aggregating red blood cells for hematopathology” by Émilie Franceschini. The number of questions at the end of each of the 33 presentations was only a reflection of their high quality, sparking interest and cross-disciplinary scientific discussions, entirely in line with what the AFAPC wishes to promote.The two Rocard 2022 prizes (prize of the Société Française d’Acoustique to distinguish promising young researchers after their PhD) were awarded to Xinxin Guo and Matthieu Malléjac during this edition.Alain Lhémery (CEA-LIST, France), Samuel Raetz (Le Mans Université, France), SFA / GAPSUS, Nader Saffari (UCL, UK), Theodosia Stratoudaki (University of Strathclyde, UK), IOP / PAG.

Research in the Department of Music Technology and Acoustics of the Hellenic Mediterranean University: An Overview and Prospects

The Department of Music Technology and Acoustics of the Hellenic Mediterranean University offers a unique higher education program in Greece, addressing the growing demand for specialists in music technology, sound technology, and acoustics. It aims to educate specialized professionals in the rapidly advancing scientific fields of music technology and acoustics, mainly driven by the swift progress in electronic technology. The Department aims to address a gap in the professional market by producing highly skilled graduates, capable not only of keeping up with the latest scientific and technological developments but also of leading the way by introducing innovative approaches and methods. The Department combines art, science, and technology, focusing on sound recording, analysis, synthesis, and music production. Music technology encompasses various cutting-edge fields such as network music performance, artificial intelligence in music, and music embodiment. Acoustics refers to fundamental aspects of sound as well as its generation, transmission, and related phenomena. It includes research fields such as physical acoustics, optoacoustics, and vibroacoustics. This overview presents the research activities, methodologies, and results. A discussion of future research works and pointers to future technological evolution towards real-world music and acoustics applications is also provided.

Helmholtz-Rayleigh Interdisciplinary Silver Medal in Computational Acoustics, Physical Acoustics, and Engineering Acoustics 2024: D. Keith Wilson

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.

Large-chamber reciprocity calibration for microbarometers

The Penn State Applied Research Laboratory (PSU) and Sandia National Laboratories (SNL) have implemented a reciprocity-based primary calibration technique in SNL’s infrasound calibration chamber. The goal in this work is primary calibration of microbarometers from 0.01 to 10.0 Hz. The National Center for Physical Acoustics at the University of Mississippi designed and built the chamber, which SNL has modified and currently operates. This chamber incorporates two moving coil loudspeakers capable of operating in receive and transmit mode. PSU developed the calibration technique and the required electronics to take advantage of these two reciprocal loudspeakers, while SNL installed this hardware and made the required test measurements. Because the chamber is large (1400 l), the chamber volume dominates the acoustical admittance thereby reducing the dependence of the calibration on the physical characteristics of the loudspeakers and reducing calibration uncertainty. However, laboratory tests have found increased uncertainty at very low frequencies ( < 0.05 Hz). This is due to reduced loudspeaker response and increasing noise within the chamber at these frequencies. This talk will discuss the large-chamber reciprocity method, important considerations for reducing uncertainty in this implementation, and limitations of this method.

Настройка функции временной регулировки чувствительности ультразвуковой аппаратуры по боковому цилиндрическому отражателю при диагностировании деталей подвижного состава

To increase the efficiency of the use of rolling stock, methods and means of technical diagnostics have been developed, which are used during maintenance and repairs, as well as an independent technological process. Diagnosis makes it possible to increase the availability coefficient, the probability of trouble-free operation, repair and control suitability of rolling stock, reduce the cost of its operation and the complexity of technological processes. The complex of test diagnostic measures includes operations of ultrasonic non-destructive testing of railway rolling stock parts and assemblies for the absence of internal unacceptable irregularities. Pulse-echo method, which refers to reflection methods, has become the most wide-spread among ultrasonic control methods. One of the most important operations in the process of ultrasonic testing is to adjust the sensitivity of ultrasonic equipment. The article focuses on the results of a study on the development of a non-etalon method for adjusting the function of temporary sensitivity ultrasonic equipment setting when diagnosing rolling stock parts, taking into account the attenuation of ultrasound along a lateral cylindrical reflector. To implement the method, a new mathematical apparatus has been developed, which is based on the key laws of physical acoustics, as well as the methods of mathematical and physical modeling. The non-standard adjustment of the temporary sensitivity setting function allows to get rid of the disadvantages when using tuning samples with artificial reflectors. A program NDTRT TSA SCR F-BCR has been developed to automate calculations when diagnosing railway rolling stock parts using the ultrasonic method and taking into account the attenuation of the ultrasonic wave along a lateral cylindrical reflector.

48th Winter School on Wave and Quantum Acoustics XLVIIth Winter School on Environmental Acoustics and Vibroacoustics Szczyrk, Poland, February 25 – March 1, 2019

48th Winter School on Wave and Quantum Acoustics constituted platforms for sharing the results and achievements obtained in different branches of physical acoustics (e.g. molecular acoustics, quantum acoustics, acousto-optics, magnetoacoustics, photoacoustics, acoustics of solid state, acoustic emission etc.). Moreover, researches in some selected topics related to those mentioned above (e.g. optoelectronics, relaxation processes) were presented during the school. Conference consisted of 15th Workshop on Acoustoelectronics and 15th Workshop on Molecular Acoustics, Relaxation and Calorimetric Methods. However, there is a possibility of organizing workshops on other subjects in the future. We would like to invite scientific centers and groups to cooperate in organizing workshops on the subjects of their interests. XLVIIth Winter School on Environmental Acoustics and Vibroacoustics was the forum for all environmental and vibroacoustics fields. Particularly it concerned traffic noise, vibroacoustics of machines, room acoustics, building acoustics, noise protection and similar problems.

49th Winter School on Wave and Quantum Acoustics XLVIIIth Winter School on Environmental Acoustics and Vibroacoustics Szczyrk, Poland, February 24–27, 2020

49th Winter School on Wave and Quantum Acoustics constituted platforms for sharing the results and achievements obtained in different branches of physical acoustics, as molecular acoustics, quantum acoustics, acousto-optics, magnetoacoustics, photoacoustics, acoustics of solid state, acoustic emission, and others. Moreover, researches in some selected topics related to those mentioned above (e.g. optoelectronics, relaxation processes) were presented during the school. The conference consisted of the 16th Workshop on Acoustoelectronics and the 16th Workshop on Molecular Acoustics, Relaxation and Calorimetric Methods. However, the organizers are opened to organizing workshops on other subjects in future. We would like to invite scientific centers and other professional groups to cooperate in organizing workshops on the subjects of their interests. XLVIIIth Winter School on Environmental Acoustics and Vibroacoustics was a forum for all environmental and vibroacoustics fields. Particularly it was concerned with traffic noise, vibroacoustics of machines, room acoustics, building acoustics, noise protection and similar problems. During the Conference, seminars on “Measurement of noise and vibration at the workplace” and Environmental noise monitoring”, combined with measurement workshops, were organised in association with SVANTEK. The Conferences began with the special, joined session dedicated to celebration of the 15th Jubilee Conference Integrated Optics – Sensors, Sensing Structures and Methods. In summary, 48 people participated in Conferences and seminars, presenting 37 lectures, reports and posters. In this issue one can find abstracts of some lectures and posters, which were presented during the Conferences.

Time-domain simulation of acoustic wave scattering and internal propagation from a gas bubble of various shapes.

Acoustic scattering and resonances of gas bubbles are computed using a time-domain simulation based on numerical solutions of the conservation laws. The time histories of scattered pressure and fluid velocity, outside and inside the bubble, are obtained simultaneously from an immersed-boundary method allowing for the investigation of exterior and interior fields for non-spherical geometries. The acoustic resonances of the bubble are investigated for various bubble sizes, shapes, and inner gas parameters and compared in limiting cases to the partial wave scattering solutions for spherical bubbles. The dynamics of the gas motion and its associated contribution to resonance response has received little attention in previous analytical and numerical formulations. In this study, the acoustic propagation and motion inside the interior gas is investigated with respect to the monopole resonance with the combined time-domain simulation and immersed-boundary method. For the non-spherical prolate and oblate shapes, the scattering and resonance behaviors are compared with the approximate analytical results based on the shape factor method. The simulation method can be extended to less-understood shapes relevant to underwater and physical acoustics, such as "pancake-shaped" or "cigar-shaped" bubbles, as well as to spatial and time-dependent forcing.

Loudness in rooms and the sound strength parameter: Linking perception and physical acoustics

Loudness as a perceptual phenomenon has been extensively studied within psychoacoustics. In room acoustics, however, the psychoacoustical factors influencing loudness have yet to be incorporated into standard parameters such as sound strength (G). G is the decibel ratio of the integrated energy of a room impulse response (RIR) compared to the same source located 10m away in a free field. The purpose of this study was to determine how the physical RIR properties measured by G relate to perceived loudness in the same room. Listeners were asked to match pink noise presented anechoically to the perceived loudness of the same noise in a simulated room. Listeners could continuously adjust the level of the anechoic reference. Room simulations were rendered over a 36-channel loudspeaker array in an anechoic chamber. Loudness matches were performed for different room types, source-receiver distances, and source powers, which produced received sound levels between 35 and 85 dBA. Results show a relatively linear relationship between loudness and G. However, it is clear that G underpredicts loudness ratings at higher sound levels. This demonstrates a more complex relationship between G and loudness. Effects of room type and source-receiver distance appear to introduce additional complexity not represented by G.

Tailoring nonlinear ultrasound beams using acoustic lenses

Acoustic holographic lenses, i.e., acoustic holograms, can tailor ultrasound beams to precisely construct elaborate focal patterns. Due to their valuable capabilities, acoustic holograms are being rapidly investigated for a wide range of applications in physical acoustics and biomedical ultrasound. Modeling and demonstrating acoustic holograms in linear regimes is well documented in the literature. However, Acoustic holograms have the potential to improve the precision and affordability of therapeutic high-intensity focused ultrasound (HIFU). In this work, we will show the effects of nonlinear propagation on ultrasound fields tailored by acoustic holograms. The intensity-dependent effects of harmonic generation, diffraction, and nonlinear gain on the constructed pressure pattern are discussed. In addition, an accelerated method for simulating high-intensity 3D holographic ultrasound is introduced. We will show how the proposed algorithm greatly reduces the computational load for designing and predicting high-intensity holographic ultrasound patterns. This expedites the procedure of designing the acoustic lens, which allows for a more rapid and seamless implementation, especially in medical settings.

Detection and estimation of rainfall from broadband acoustic signals

Jeff Nystuen contributed major advances in our understanding of the physical acoustics of rain falling on the ocean, culminating in his pioneering work quantifying rainfall from the shape of the acoustic spectrum. Ma and Nystuen [JAOT (2005)] exploited Vagle’s wind spectrum to self-calibrate hydrophones for long deployments as acoustic rain gauges. Their algorithm predominantly relied on 3 narrowband frequencies to detect rainfall, and correlated the rainfall amount with the power spectral density (PSD) at 5kHz. Recent research at UMass Dartmouth built upon the foundational work of Nystuen, Ma and others to examine how much additional information can be gleaned from broadband acoustic spectra. These algorithms exploit Principal Component Analysis and Linear Discriminant Analysis for rainfall detection, coupled with Error-Correcting Output Codes (ECOC) for quantizing rainfall estimation. Testing on 5 months of 3-minute PSDs from a noisy cove found a detection probability of 78 ± 5% with a 1.1 ± 0.3% false alarm rate. Moreover, ECOC-based hourly rainfall estimates achieved 0.97 ± 0.01 correlation with rainfall measurements at a co-located meteorological station. This talk plans to present results from a recent 6 week coastal deployment in deeper water. [Work supported by ONR/UMassD MUST program]

Acoustics demonstration extravaganza

The Education in Acoustics and Physical Acoustics committees are pleased to present an Acoustics Demonstration Extravaganza - a showcase of demonstrations and apparatus to inspire and challenge your understanding of acoustics and vibration phenomena. In the spirit of the “Circus of Acoustics” demonstration show from the June 2002 ASA 143 Pittsburgh meeting [J. Acoust. Soc., Am., 111, 5, Pt2, p. 2451, (2002) session 4pPAb] this session will consist of several short demonstrations covering a wide variety of acoustics and vibration topics. Among the demonstrations intended to be shown are the following (there may be some last-minute additions or substitutions depending on equipment and presenter availability): Simple Sound Sources: Directory patterns and frequency spectrum characteristics of monopole, dipole, and quadrupole sources, the pressure doubling effect of a baffle, and a beam-forming array. Radiation of Sound from Plates: Demonstration of the radiated intensity from various vibrational modes of a simply supported thin plate. Strings of Pearls: Modes of vibration for a N-DOF mass-spring system and standing waves on a compound string comprised of a two string segments with different densities. Burning Wire of Death: Standing waves on a nichrome wire carrying a high current so it glows red at nodes. The Song of the Singing Rod: The singing rod demonstration is commonly used to describe longitudinal waves in a free-free rod. However, if the length of the rod is adjusted just right, a nonlinear pulsating effect is observed resulting from modal coupling of transverse bending modes and either subharmonic longitudinal modes or torsional modes. Nonlinear Oscillations in a Membrane: A membrane is driven with a large amplitude, so the vibration becomes nonlinear. As the frequency sweeps up and then down, the amplitude jumps and follows a hysteresis loop characteristic of a stiffening nonlinear spring. Demonstration apparatus of the Cochlea (designed by Robert Keolian): A mechanical hydrodynamic analog model of the basilar membrane in the cochlea illustrating von Békésy's classical passive tonotopic traveling wave as an explanation of how the ear responds to different frequencies. Acoustic Resonator Rockets: A pair of lightweight Helmholtz Resonators, balanced on a pivot, will rotate when exposed to a loud amplitude sound at their resonance frequency. Acoustic Filters: An audible and visual demonstration of low-pass, high-pass, and band-stop acoustic filters using PVC pipes. Vocal Tract Models: A collection of short pipes with varying cross-sectional areas (designed by Takayuki Arai) that produce vowel sounds and may be used to model the acoustics of speech. Speed of Sound: A series of short demonstrations that illustrate the effect of temperature on the speed of sound in air, sound speed dependence on gas composition, and the effect of bubbles on the speed of sound in water. Fluid Loading of a Plate: A comparison of the vibration response of a vibrating plate, and the audibly radiated sound, when the plate is in air versus submerged in water. Rectangular Waveguide: Plane waves will propagate down a waveguide without decay at all frequencies, but non-plane wave modes will propagate only if driven above the cut-on frequency. When driven below the cut-on frequency, non-plane modes become evanescent and decay exponentially. Baseball Bat Piano: The hollow cylindrical barrels of metal and composite softball bats exhibit cylindrical shell vibrational modes. A collection of softball bats with hoop-mode frequencies corresponding to a musical scale may be played like a xylophone.

Helmholtz-Rayleigh Interdisciplinary Silver Medal in Biomedical Acoustics and Physical Acoustics 2023: Vera A. Khokhlova

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.

A simulation method on target strength and circular SAS imaging of X-rudder UUV including multiple acoustic scattering

Target strength (TS) and circular synthetic aperture sonar (CSAS) images provide essential information for active acoustic detection and recognition of non-cooperative unmanned undersea vehicles (UUVs), which pose a significant threat to underwater preset facilities. To access them, we propose an iterative physical acoustics (IPA)-based method to simulate the multiple acoustic scattered fields on rigid surfaces in high-frequency cases. It uses the Helmholtz integral equation with an appropriate Green's function in terms of the Neumann series, and then incorporates the ideas of triangulation and iteration into a numerical implementation. Then two approximate analytic formulae with precise physical meanings are derived to predict the TS and CSAS images of concave targets, respectively. There are no restrictions on the surface's curvature and the order of multiple scattering. The method is validated against the finite element method (FEM) for acoustic scattering from a sphere segment and against an experiment involving an X-rudder UUV's stern. On this basis, we simulate and analyze the TS and CSAS images of an X-rudder UUV. In addition, the influence of the angle of adjacent rudders on the multiple scattering characteristics is discussed. Results show that this method can potentially predict accurate UUV features, especially the multiple scattered features.

Effect of Face Masks on Speech Intelligibility

With the advent of COVID, the wearing of face covering has been obligatory in both medical and everyday life. This paper describes three experiments undertaken to establish the effect of face coverings on speech sound power, speech directivity and speech intelligibility. The experiments used two different approaches acoustic measurements and word scores. The face coverings assessed were a 'standard blue' surgical mask, a typical fabric mask, and a plastic transparent visor. The results showed that non-native English speakers had by far the most difficulty in comprehending the English language speech when face coverings were worn in speech intelligibility tests, as measured using phonetically balanced word lists. All the masks were found to noticeably affect speech intelligibility, with the surgical mask having the least detrimental effect. The results are also compared to objective measurements of their physical acoustics characteristics to establish their performance.

Physical Acoustics Methods for Assessing Hydrogen Embrittlement in PT-7M Grade Titanium Alloy

Physical Acoustics Methods for Assessing Hydrogen Embrittlement in PT-7M Grade Titanium Alloy

Multimodal antireflective coatings for perfecting anomalous reflection from arbitrary periodic structures

Metasurfaces possess vast wave-manipulation capabilities, including reflection and refraction of a plane wave into non-standard directions. This requires meticulously-designed sub-wavelength meta-atoms in each period of the metasurface which guarantee unitary coupling to the desired Floquet-Bloch mode or, equivalently, suppression of the coupling to other modes. Herein, we propose an entirely different scheme to achieve such suppression, alleviating the need to devise and realize such dense scrupulously-engineered polarizable particles. Extending the concept of anti-reflective coatings to enable simultaneous manipulation of multiple modes, we show theoretically and experimentally that a simple superstrate consisting of only several uniform dielectric layers can be modularly applied to \textit{aribtrary} periodic structures to yield perfect anomalous reflection. This multimodal anti-reflective coating (MARC), designed based on an analytical model, presents a conceptually and practically simpler paradigm for wave-control across a wide range of physical branches, from electromagnetics and acoustics to seismics and beyond.

Acoustic Shooting and Bounce Ray Method for Calculating Echoes of Complex Underwater Targets

The acoustic scattering characteristics of a target are of great significance to the design of underwater acoustic detection systems. With the improvement in underwater weapon detection ability, the precision and accuracy of underwater target echo characteristic simulations are required to be higher and higher. The traditional underwater target simulation based on bright spot can no longer meet the needs of an underwater acoustic detection system for targeting fine feature recognition. This paper proposes a calculation using the fine complex underwater target echo bounce beam line method, in addition to the establishment of a bandwidth signal time domain calculation model and the integral dimension reduction to accelerate the algorithm on the basis of thorough target subspace division, combined with the geometrical acoustics method (GA) and physical acoustics (PA) for the pipeline space beam propagation tracking and aperture sound field to solve and realize the acoustic scattering characteristic calculation of a complex underwater target. Finally, the proposed method was verified by the Benchmark standard submarine. The accuracy and computational efficiency of the PA acceleration method are given, and the integrity of the target information calculated by the method is verified by acoustic ISAR imaging analysis. The simulation results show that the pipeline method of bouncing an acoustic beam is suitable for the simulation of complex underwater, target-wide band fine echoes.

Graphical acoustic computing method incorporated with the shooting and bouncing ray: application to target strength prediction of concave objects with second-order reflection effects

The acoustic backscattering prediction of underwater targets has been drawing concerns from underwater vehicle designers. A graphical acoustic computing method combined with the shooting bouncing ray method (GRACO-SBR) is introduced to solve the acoustic target strength of complex underwater target with concave surfaces. The graphical acoustic computing (GRACO) is an asymptotic method based on physical acoustics. Aided with OpenGL 3D graphical rendering pipeline, this method can process the acoustic integration parallelly and efficiently. Since the traditional GRACO only considers the first-order scattering, the shooting and bouncing ray (SBR) is compounded with the GRACO to cope with the higher-order scattering of concave structures. The target strength of an impedance sphere is solved with several different methods including the GRACO. The results show that the GRACO has an outstanding advantage of the efficiency over the finite element method (FEM) and the traditional Kirchhoff approximation at minor cost of the accuracy in high frequency range. Besides, the prediction of the backscattering of a dihedral corner reflector tells that the GRACO-SBR which considers the second-order scattering can acquire much more accurate solutions than the traditional GRACO method. Further, a stern with cross rudders is considered by both GRACO and GRACO-SBR, and the solutions show that the second-order scattering cannot be overlook when predicting the backscattering of concave structures.