Use Of Sound Research Articles

Multifunctional Asymmetric Sound Manipulations by a Passive Phased Array Prism

Asymmetric acoustic manipulations (AAMs) attract increasing attention for applications in integrated and architectural acoustics. However, because a planar phased array system has the same phase distribution on both sides, designing a monolayer device with asymmetric phase modulation is a real challenge. This work experimentally realizes four types of phased array prisms with different AAM effects arising from asymmetric phase distributions, created by different exit interfaces on either side of a prism. With broad bandwidth, multifunctional AAMs, passive structure, and easy fabrication, these prisms offer a fresh approach to creating $e.g.$ multifunctional acoustic rectifiers and diodes.

Three-dimensional large-scale acoustic invisibility cloak with layered metamaterials for underwater operation

A class of three-dimensional acoustic cloak for underwater operation is designed by using a multi-area coordinate transformation method. To overcome the difficulty of achieving materials with the ideal parameters of the cloak in nature, layered metamaterials consisting of mercury and water are designed based on effective medium theory. The acoustic properties of the layered metamaterials can be characterized by the anisotropic densities and isotropic modulus, which can satisfy the material requirements of the cloak shell. This design has many advantages over previous designs of acoustic cloak, including a large cloaking area, omnidirectional invisibility, broad working frequency and easier design methodology. Our transformation strategy and method of metamaterials design offer a cost-effective way and efficient technique for fabricating a large-scale cloak. Excellent invisibility is achieved by using simulations based on the finite element method. The good cloaking performances have demonstrated great potential in the promotion of the practical applications of a large-scale acoustic cloak, especially for low-frequency sound manipulation underwater.

Reflected acoustic wavefront manipulation by an ultrathin metasurface based on three-dimensional generalized Snell’s law

We theoretically derive three-dimensional (3D) generalized Snell’s law which is demonstrated by reflected wavefront manipulations based on ultrathin quasi-3D acoustic metasurfaces. Acoustic metasurfaces with a deep subwavelength thickness of λ/10 are constructed with 16 unit cells composed of a straight pipe and two ring-like Helmholtz resonators. Based on the 3D generalized Snell’s law, many fascinating reflected wavefront manipulations in 3D space are realized separately, including anomalous reflections, point focusing, line focusing in two perpendicular directions, non-diffracting Bessel beam and self-bending beam. Our results provide a new design methodology for 3D sound wavefront manipulations and practical applications of 3D sound devices.

The Present and Future Role of Acoustic Metamaterials for Architectural and Urban Noise Mitigations

Owing to a steep rise in urban population, there has been a continuous growth in construction of buildings, public or private transport like cars, motorbikes, trains, and planes at a global level. Hence, urban noise has become a major issue affecting the health and quality of human life. In the current environmental scenario, architectural acoustics has been directed towards controlling and manipulating sound waves at a desired level. Structural engineers and designers are moving towards green technologies, which may help improve the overall comfort level of residents. A variety of conventional sound absorbing materials are being used to reduce noise, but attenuation of low-frequency noise still remains a challenge. Recently, acoustic metamaterials that enable low-frequency sound manipulation, mitigation, and control have been widely used for architectural acoustics and traffic noise mitigation. This review article provides an overview of the role of acoustic metamaterials for architectural acoustics and road noise mitigation applications. The current challenges and prominent future directions in the field are also highlighted.

Análise de oportunidades de desenvolvimento de consciência de abertura de vogais orais do português brasileiro em cinco manuais de português língua estrangeira

Este artigo tem por objetivo investigar as oportunidades de desenvolvimento de consciência fonológica das vogais médias-baixas do português /ε/ e /ͻ/ em cinco materiais didáticos voltados ao ensino do português brasileiro para aprendizes estrangeiros. Para a realização desta pesquisa, foram consultados os seguintes materiais didáticos: Brasil Intercultural 1 e 2; Brasil Intercultural 3 e 4; Novo Avenida Brasil 1; Diálogo Brasil - Curso Intensivo de Português para Estrangeiros e Passagens - Português do Brasil para estrangeiros. Buscamos avaliar, nos materiais analisados, as oportunidades de desenvolvimento de habilidades de consciência fonológica, como reconhecimento e manipulação (ALVES, 2012). Para a análise das vogais, recorremos aos pressupostos teóricos da Fonologia Autossegmental (CLEMENTS; HUME, 1995). Ao analisar os materiais didáticos, verificamos que os exercícios propostos nos cinco livros selecionados são, basicamente, de discriminação auditiva, de classificação e de pronúncia em repetição e que não oportunizam o desenvolvimento de consciência de abertura das vogais orais do português brasileiro, uma vez que não estimulam a percepção de regularidades do sistema fonológico e a manipulação de seus constituintes. Propomos, após a análise, atividades para o nível A1.

Sample-level sound synthesis with recurrent neural networks and conceptors.

Conceptors are a recent development in the field of reservoir computing; they can be used to influence the dynamics of recurrent neural networks (RNNs), enabling generation of arbitrary patterns based on training data. Conceptors allow interpolation and extrapolation between patterns, and also provide a system of boolean logic for combining patterns together. Generation and manipulation of arbitrary patterns using conceptors has significant potential as a sound synthesis method for applications in computer music but has yet to be explored. Conceptors are untested with the generation of multi-timbre audio patterns, and little testing has been done on scalability to longer patterns required for audio. A novel method of sound synthesis based on conceptors is introduced. Conceptular Synthesis is based on granular synthesis; sets of conceptors are trained to recall varying patterns from a single RNN, then a runtime mechanism switches between them, generating short patterns which are recombined into a longer sound. The quality of sound resynthesis using this technique is experimentally evaluated. Conceptor models are shown to resynthesise audio with a comparable quality to a close equivalent technique using echo state networks with stored patterns and output feedback. Conceptor models are also shown to excel in their malleability and potential for creative sound manipulation, in comparison to echo state network models which tend to fail when the same manipulations are applied. Examples are given demonstrating creative sonic possibilities, by exploiting conceptor pattern morphing, boolean conceptor logic and manipulation of RNN dynamics. Limitations of conceptor models are revealed with regards to reproduction quality, and pragmatic limitations are also shown, where rises in computation and memory requirements preclude the use of these models for training with longer sound samples. The techniques presented here represent an initial exploration of the sound synthesis potential of conceptors, demonstrating possible creative applications in sound design; future possibilities and research questions are outlined.

Real-time separation of non-stationary sound fields on spheres.

The sound field separation methods can separate the target field from the interfering noises, facilitating the study of the acoustic characteristics of the target source, which is placed in a noisy environment. However, most of the existing sound field separation methods are derived in the frequency-domain, thus they are best suited for separating stationary sound fields. In this paper, a time-domain sound field separation method is developed that can separate the non-stationary sound field generated by the target source over a sphere in real-time. A spherical array sets up a boundary between the target source and the interfering sources, such that the outgoing field on the array is only generated by the target source. The proposed method decomposes the pressure and the radial particle velocity measured by the array into spherical harmonic coefficients, and recovers the target outgoing field based on the time-domain relationship between the decomposition coefficients and the theoretically derived spatial filter responses. Simulations show the proposed method can separate non-stationary sound fields both in free field and room environments, and over a longer duration with small errors. The proposed method could serve as a foundation for developing future time-domain spatial sound field manipulation algorithms.

Predicting population change from models based on habitat availability and utilization.

The need to understand the impacts of land management for conservation, agriculture and disease prevention are driving demand for new predictive ecology approaches that can reliably forecast future changes in population size. Currently, although the link between habitat composition and animal population dynamics is undisputed, its function has not been quantified in a way that enables accurate prediction of population change in nature. Here, using 12 house sparrow colonies as a proof-of-concept, we apply recent theoretical advances to predict population growth or decline from detailed data on habitat composition and habitat selection. We show, for the first time, that statistical population models using derived covariates constructed from parametric descriptions of habitat composition and habitat selection can explain an impressive 92% of observed population variation. More importantly, they provide excellent predictive power under cross-validation, anticipating 81% of variability in population change. These models may be embedded in readily available generalized linear modelling frameworks, allowing their rapid application to field systems. Furthermore, we use optimization on our sample of sparrow colonies to demonstrate how such models, linking populations to their habitats, permit the design of practical and environmentally sound habitat manipulations for managing populations.

Active times for acoustic metamaterials

Abstract Initially proposed to achieve strong noise isolation levels beyond the mass-density law, acoustic metamaterials (AMMs) have now overturned the conventional views in all aspects of sound propagation and manipulation. In fact, within the last two decades, these artificial materials have enabled improved control over the propagation of sound waves by allowing one to engineer macroscopic effective properties well beyond what is naturally available. In this review, we first trace the development of passive AMMs from their initial realizations based on locally resonant structures to their more advanced versions, like space-coiling, holey and labyrinthine metamaterials, Willis materials, and subwavelength crystalline metamaterials, highlighting their basic working principles and applications. We then survey more recent research topics, including non-Hermitian, non-reciprocal, and topological acoustic metamaterials. Altogether, this paper provides a comprehensive overview of research on acoustic metamaterials, and highlights prominent future directions in the field, including topological and active metamaterials.

Acoustic accelerating beam based on a curved metasurface

General relativity directly relates the curvature of spacetime to the energy and momentum whatever matter and radiation are present. In this letter, the different curved shapes of acoustic metasurfaces are used to mimic various curved spacetimes, while the different phase shift distributions are used to mimic different movements in the curved spacetime. Consequently, a new degree of freedom is attained by introducing the curved geometry of the metasurface, which is fully different from the straight geometrical structures in conventional acoustic metasurfaces. We have experimentally implemented multi-directional transmission by a curved metasurface. Furthermore, as the general relativity is constructed using tensors, it exhibits general covariance: its laws share the same form in all coordinate systems. With the general covariance, covariant structures can produce an identical acoustic field by the covariant transformation between different curved metasurfaces, such as Rindler-analogous transformation, which has been experimentally realized with different curved metasurfaces. This general covariant design method can be extended to many other sound manipulations.

Surface acoustic waves over bianisotropic metasurfaces

Metasurfaces are the two-dimensional planarized analogues of metamaterials, yielding unique sound manipulation along a surface. Our group recently proposed the concept of bianisotropic metasurfaces achieved by exploiting the strong nonlocal coupling between neighboring vibrating units, yielding anisotropic impedance in airborne acoustics, and we have applied this property to realize acoustic hyperbolic metasurfaces, which require extreme impedance anisotropy. In this talk, we investigate the wave propagation properties of bianisotropic metasurfaces and report all-angle backward-wave propagation on the surface. By carefully designing the coupling between unit cells, both negative phase index and energy index for surface acoustic waves are observed above the metasurface for all propagation directions, hence realizing converging waves for a radiating point source. Since in bianisotropic metasurfaces the energy can be transmitted not only through surface waves, but also through the coupling units, negative energy index for surface waves does not violate energy conservation laws, as it can be sustained by a positive energy flow within the connected unit cells composing the metasurface.

Conformally Mapped Multifunctional Acoustic Metamaterial Lens for Spectral Sound Guiding and Talbot Effect.

We demonstrate a conformally mapped multifunctional acoustic metamaterial Mikaelian lens. Mikaelian lens is a gradient medium with a hyperbolic secant refractive index profile that can realize functions like beam self-focusing. Unlike the conventional design approaches, with a conformal transformation method, only isotropic material parameters with gradient refractive index profiles are required for the construction of such lens. To realize desired gradient index distribution, we carefully design a new type of cross-channel-shaped acoustic metamaterial, whose refractive index can be effectively modulated by simply changing the slit opening size. The distinct capabilities of the metamaterial Mikaelian lens in manipulating acoustic waves are experimentally verified with the fabricated sample. Simultaneous sound guiding and Talbot effects, which normally require respective geometrical and wave acoustic approximations, are observed in simulations and experiments. Furthermore, those effects of shaping acoustic wave propagations were validated within a relatively wide frequency range. Our study reveals how the conformal transformation method can help to bridge the ray acoustics with wave acoustics. It offers opportunities to the development of novel multifunctional acoustic devices for various applications, such as sound and particle manipulations.

Topological acoustic transports in chiral sonic crystals

<sec>Topological sound has enriched the way of implementing the sound manipulation, which can effectively suppress the backscattering due to topological protection. As an inherent longitudinal wave, sound wave has no " spin” and only supports longitudinal vibration. Creating the " pseudospin” degree of freedom is crucial to topological state for acoustic wave. In previous studies, a circulating fluid flow in the background field is introduced to break the reciprocity of wave propagation in an acoustic system, which still faces technically a challenge. On the other hand, acoustic analogues of quantum spin Hall state and valley Hall state are realized by relying on the Kramers doublet in the lattices with <i>C</i><sub>6</sub> symmetry and the broken mirror symmetry or inversion symmetry, respectively. In these cases, the distributions of acoustic energy flux in the unit cells emulate the pseudospins. Based on the band inversion, the topological sound carrying pseudospin is implemented at the interface between topologically trivial and non-trivial sonic crystal. Because of the close relevance to the lattice symmetry, these pseudospin-based topological state in the time-reversal invariant system is sensitive to structural defects. </sec><sec>In this work, we investigate the topological sound in chiral sonic crystal consisting of resonant air tubes. The counterclockwise and clockwise length variation of air tube correspond to different topological phases. A defect meta-molecule is created at the symmetric interface, which supports resonant state in the band gap. The interface state occurs at the boundary between two opposite chiral sonic crystals. Owing to the resonant structure, we realize subwavelength topological sound transport with a subwavelength-transverse confinement. For the state carrying monopolar-mode symmetry, it is expected to preserve the mode symmetry under randomly introduced defects. As anticipated, the numerical results show that the topological sound has very strong robustness against various defects, such as the variation of positions and length of air tube. Finally, we utilize the field symmetry of topological sound in chiral sonic crystal to realize robust edge transport along soft or rigid boundary. Through the mirror symmetry operation of soft or rigid boundary, we construct an interface between the real lattice and its virtual image. The approach greatly reduces the dimension of sonic crystal device. Our work may conduce to the advances in topological acoustics, since the subwavelength-scale topological state promotes the applications of miniaturized acoustic devices.</sec>

Deepening subwavelength acoustic resonance via metamaterials with universal broadband elliptical microstructure

Slow sound is a frequently exploited phenomenon that metamaterials can induce in order to permit wave energy compression, redirection, imaging, sound absorption, and other special functionalities. Generally, however, such slow sound structures have a poor impedance match to air, particularly at low frequencies and consequently exhibit strong transmission only in narrow frequency ranges. This therefore strongly restricts their application in wave manipulation devices. In this work, we design a slow sound medium that halves the effective speed of sound in air over a wide range of low frequencies (hence our referral to the microstructure as “broadband”), whilst simultaneously maintaining a near impedance match to air. This is achieved with a rectangular array of acoustically rigid cylinders of elliptical cross section, a microstructure that is motivated by combining transformation acoustics with homogenization. Microstructural parameters are optimized in order to provide the required anisotropic material properties as well as near impedance matching. We then employ this microstructure in order to halve the size of a quarter-wavelength resonator (QWR) or equivalently to halve the resonant frequency of a QWR of a given size. This provides significant space savings in the context of low-frequency tonal noise attenuation in confined environments where the absorbing material is adjacent to the region in which sound propagates, such as in a duct. We employ the term “universal” since we envisage that this microstructure may be employed in a number of diverse applications involving sound manipulation.

VJ Vertov: from the compositing interface to the use of the projection space

Once digitization had been standardized in the process of audiovisual creation, there has been an improvement over the last decades in the efficiency of storage, coding and transfer systems, an integration of editing and compositing procedures, an increased potential for real-time image and sound manipulation and an increase in the mediation of software and its interface in creative processes. On the basis of both a representative work – Chelovek S Kino-Apparatom ( Man with a Movie Camera, Dziga Vertov, 1929) − and the considerations of Lev Manovich, one of the leading theorists on the subject, this essay is intended as a starting point for addressing issues related to the mutations produced in the traditional concept of film editing as a consequence of the digitization process described above. For this purpose, the authors summarize the results of practical research based on the real-time filmic reinterpretation of the film’s editing.

Fine manipulation of sound via lossy metamaterials with independent and arbitrary reflection amplitude and phase

The fine manipulation of sound fields is critical in acoustics yet is restricted by the coupled amplitude and phase modulations in existing wave-steering metamaterials. Commonly, unavoidable losses make it difficult to control coupling, thereby limiting device performance. Here we show the possibility of tailoring the loss in metamaterials to realize fine control of sound in three-dimensional (3D) space. Quantitative studies on the parameter dependence of reflection amplitude and phase identify quasi-decoupled points in the structural parameter space, allowing arbitrary amplitude-phase combinations for reflected sound. We further demonstrate the significance of our approach for sound manipulation by producing self-bending beams, multifocal focusing, and a single-plane two-dimensional hologram, as well as a multi-plane 3D hologram with quality better than the previous phase-controlled approach. Our work provides a route for harnessing sound via engineering the loss, enabling promising device applications in acoustics and related fields.

Does material matter in designing better acoustic metasurfaces?

Finite element simulations reveal important features of the materials used for sound manipulation and their impact on performance.

Home use of binocular dichoptic video content device for treatment of amblyopia: a pilot study

To evaluate the efficacy of the BinoVision home system as measured by improvement of visual acuity in the patient's amblyopic eye. An open-label prospective pilot-trial of the system was conducted with amblyopic children aged 4-8years at the pediatric ophthalmology unit, Tel-Aviv Medical Center, January 2014 to October 2015. Participants were assigned to the study or sham group for treatment with BinoVision for 8 or 12weeks. Patients were instructed to watch animated television shows and videos at home using the BinoVision device for 60minutes, 6days a week. The BinoVision program incorporates elements at different contrast and brightness levels for both eyes, weak eye tracking training by superimposed screen images, and weak eye flicker stimuli with alerting sound manipulations. Patients were examined at 4, 8, 12, 24, and 36weeks. A total of 27 children were recruited (14 boys), with 19 in the treatment group. Median age was 5years (range, 4-8years). Mean visual acuity improved by 0.26 logMAR lines in the treatment group from baseline to 12weeks. Visual acuity was improved compared to baseline during all study and follow-up appointments (P<0.01), with stabilization of visual acuity after cessation of treatment. The sham group completed 4weeks of sham protocol with no change in visual acuity (P=0.285). The average compliance rate was 88%±16% (50% to 100%) in treatment group. This pilot trial of 12weeks of amblyopia treatment with the BinoVision home system demonstrated significant improvement in patients' visual acuity.

Extraordinary wave phenomena in active acoustic metamaterials

Non-Hermitian sonic metamaterials are artifical acoustic media that exploit gain and loss as an extra degree of freedom to induce novel physical effects that cannot be obtained with lossless or trivial lossy systems. In this talk, we will review our recent theoretical and experimental results about one-dimensional non-Hermitian acoustics, highlighting the ability of active metamaterials to overcome limitations of passive metamaterials by engineering the acoustic power flow at the microscopic scale. We will discuss various experiments employing a set of electroacoustic resonators in a pipe, engineered to provide tailored distributions of acoustic gain or loss, and discuss the potentials of such systems in terms of sound manipulation. Altogether, our work points out the large potential and rich physics of non-Hermitian acoustic metamaterials.

Breaking the barriers: advances in acoustic functional materials

Abstract Acoustics is a classical field of study that has witnessed tremendous developments over the past 25 years. Driven by the novel acoustic effects underpinned by phononic crystals with periodic modulation of elastic building blocks in wavelength scale and acoustic metamaterials with localized resonant units in subwavelength scale, researchers in diverse disciplines of physics, mathematics, and engineering have pushed the boundary of possibilities beyond those long held as unbreakable limits. More recently, structure designs guided by the physics of graphene and topological electronic states of matter have further broadened the whole field of acoustic metamaterials by phenomena that reproduce the quantum effects classically. Use of active energy-gain components, directed by the parity–time reversal symmetry principle, has led to some previously unexpected wave characteristics. It is the intention of this review to trace historically these exciting developments, substantiated by brief accounts of the salient milestones. The latter can include, but are not limited to, zero/negative refraction, subwavelength imaging, sound cloaking, total sound absorption, metasurface and phase engineering, Dirac physics and topology-inspired acoustic engineering, non-Hermitian parity–time synthetic active metamaterials, and one-way propagation of sound waves. These developments may underpin the next generation of acoustic materials and devices, and offer new methods for sound manipulation, leading to exciting applications in noise reduction, imaging, sensing and navigation, as well as communications.