The present article is on pulsatile hemodynamics‐induced sound‐based diagnosis of stenosis in compliant arteries of three types: Coronary, carotid, and femoral. Considering axisymmetric stenosis in straight arteries along with clinically observed dimensions of the arteries and enveloping tissue, the present numerical study considers blood as a Newtonian fluid and both artery and tissue as isotropic and geometrically nonlinear (materialistically linear) solid. For the physiological fluid flexible‐structure acoustic interaction (FfSAI) study, an in‐house multiphysics solver is used for a parametric study—using various stenosis level S$$ S $$ (60%, 70%, and 80%) and stenosis length Lst$$ {L}_{\mathrm{st}} $$ (2D and 4D); for each of the arteries. With increasing S$$ S $$ , an increase in acoustic acceleration's FFT spectrum‐based cut‐off frequency fc$$ {f}_c $$ is found—indicating possibility of quantitative phonoangiographic diagnosis. The variation of this frequency fc$$ {f}_c $$ with S$$ S $$ follows similar trend as that of frequency calculated by pressure fluctuation's FFT spectrum, thus correlating the hemodynamics as the cause for generation of the sound/bruits. Also, a flow‐visualization‐based frequency, which is calculated using vortex length and velocity during vortex dissipation stage, matches reasonably (≤ 15% difference) with the cut‐off frequency of pressure fluctuation. For the first time in the literature, our sound velocity level‐based study shows over‐prediction of stenosis by neglecting flow‐induced tissue deformations. This implies the importance of modeling structural flexibility, along with flow and acoustics while developing a computational Point‐of‐Care diagnostic tool. Finally, using analytical method for acoustics, a computationally efficient semi‐analytical FfSAI approach is proposed. The present work is significant since an accurate and computationally efficient framework and flow‐physics‐based analysis are presented for phonoangiographic diagnosis of stenosed arteries of three types.
Agreed Fair and Equitable Dispersion of aircraft is an aspirational objective by many airports to alleviate the burden of noise from aircraft/airspace changes on affected communities and a hot topic in aviation generally. A workable definition of Fair and Equitable Dispersion would, in theory, enable airspace managers and aircraft operators to design solutions to deliver quicker, quieter and cleaner journeys and more capacity for the benefit of those who use and are affected by airspace. However, reaching consensus amongst stakeholders on an agreed definition of Fair and Equitable Dispersion is highly challenging and not just a technical issue due to the substantial acoustic, health, quality of life and non-acoustic factors affecting the human perceptual response to sound in context. This paper presents findings from an independent study in the United Kingdom aimed at developing a definition of an airport’s Fair and Equitable Distribution of traffic and recommendations to inform stakeholder discussions as a stage process. To the best of the authors’ knowledge, this was the first study of its kind in the UK with this aim. Using a mix of descriptive and exploratory qualitative research techniques, the study compiles findings from reviews of aviation noise metrics, policy and technology options; an updated evidence review of health effects of aircraft noise; and an overview of the impact of non-acoustic factors. The study proposed a transdisciplinary Sound, Noise and Health Conceptual Framework and recommendations for implementation as a stage process comprised of: i locally salient non-acoustic factors derived and mapped through stakeholder engagement, ii a Health Dashboard incorporating agreed combined environmental and health metrics, iii acoustic and psychoacoustic metrics building upon a perception-based engineering approach, iv operational indicators to be agreed with local and national stakeholders, within the international context. The study posits important considerations for future air transport policy and sound, noise and health research and sets a foundation for further ongoing studies to apply the proposed Sound, Noise and Health Conceptual Framework .
This presentation introduces a novel computational model designed to simulate both sensorineural and hidden hearing loss, providing a powerful tool for architects, acousticians, and researchers to better understand and address hearing disabilities. Developed using Max/MSP, the model employs a multiband downward expander to simulate sensorineural hearing loss, with thresholds adjustable based on age and common noise-induced patterns. Hidden hearing loss, an increasingly prevalent yet under-recognized condition, is modeled through the innovative manipulation of temporal envelope (ENV) and temporal fine structure (TFS) components. By allowing users to experience these hearing impairments firsthand, the model bridges the gap between audiological data and practical application in building design and acoustic engineering. This interdisciplinary approach not only enhances our understanding of hearing loss but also has potential implications for public health, incentivizing proper ear protection, and care. The model serves as a valuable educational resource, fostering empathy and driving more inclusive design practices in architecture and acoustics.
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.
With unlimited topological modes in mathematics, the fractional orbital angular momentum (FOAM) demonstrates the potential to infinitely increase the channel capacity in acoustic-vortex (AV) communications. However, the accuracy and stability of FOAM recognition are still limited by the nonorthogonality and poor anti-interference of fractional AV beams. The popular machine learning, widely used in optics based on large datasets of images, does not work in acoustics because of the huge engineering of the 2-dimensional point-by-point measurement. Here, we report a strategy of phase-dislocation-mediated high-dimensional fractional AV communication based on pair-FOAM multiplexing, circular sparse sampling, and machine learning. The unique phase dislocation corresponding to the topological charge provides important physical guidance to recognize FOAMs and reduce sampling points from theory to practice. A straightforward convolutional neural network considering turbulence and misalignment is further constructed to achieve the stable and accurate communication without involving experimental data. We experimentally present that the 32-point dual-ring sampling can realize the 10-bit information transmission in a limited topological charge scope from ±0.6 to ±2.4 with the FOAM resolution of 0.2, which greatly reduce the divergence in AV communications. The infinitely expanded channel capacity is further verified by the improved FOAM resolution of 0.025. Compared with other milestone works, our strategy reaches 3-fold OAM utilization, 4-fold information level, and 5-fold OAM resolution. Because of the extra advantages of high dimension, high speed, and low divergence, this technology may shed light on the next-generation AV communication.
Stimulated Brillouin scattering (SBS), a coherent nonlinear effect coupling acoustics and optics, can be used in a wide range of applications such as Brillouin lasers and tunable narrowband RF filtering. Wide adoption of such technologies however, would need a balance of strong Brillouin interaction and low optical loss in a structure compatible with large scale fabrication. Achieving these characteristics in scalable platforms such as silicon and silicon nitride remains a challenge. Here, we investigate a scalable Brillouin platform combining low loss Si$_3$N$_4$ and tellurium oxide (TeO$_2$) exhibiting strong Brillouin response and enhanced acoustic confinement. In this platform we measure a Brillouin gain coefficient of 8.5~m$^{-1}$W$^{-1}$, exhibiting a twenty fold improvement over the largest previously reported Brillouin gain in a Si$_3$N$_4$ platform. Further, we demonstrate cladding engineering to control the strength of the Brillouin interaction. We utilized the Brillouin gain and loss resonances in this waveguide for an RF photonic filter with more than 15 dB rejection and 250 MHz linewidth. Finally, we present a pathway by geometric optimization and cladding engineering to a further enhancement of the gain coefficient to 155~m$^{-1}$W$^{-1}$, a potential 400 times increase in the Brillouin gain coefficient.
Controlling audible sound requires inherently broadband and subwavelength acoustic solutions, which are to date, crucially missing. This includes current noise absorption methods, such as porous materials or acoustic resonators, which are typically inefficient below 1 kHz, or fundamentally narrowband. Here, we solve this vexing issue by introducing the concept of plasmacoustic metalayers. We demonstrate that the dynamics of small layers of air plasma can be controlled to interact with sound in an ultrabroadband way and over deep-subwavelength distances. Exploiting the unique physics of plasmacoustic metalayers, we experimentally demonstrate perfect sound absorption and tunable acoustic reflection over two frequency decades, from several Hz to the kHz range, with transparent plasma layers of thicknesses down to λ/1000. Such bandwidth and compactness are required in a variety of applications, including noise control, audio-engineering, room acoustics, imaging and metamaterial design.
The boundary element method (BEM) is a powerful tool in computational acoustics, because the analysis is conducted only on structural surfaces, compared to the finite element method (FEM) which resorts to special techniques to truncate infinite domains. The isogeometric boundary element method (IGABEM) is a recent progress in the category of boundary element approaches, which is inspired by the concept of isogeometric analysis (IGA) and employs the spline functions of CAD as basis functions to discretize unknown physical fields. As a boundary representation approach, IGABEM is naturally compatible with CAD and thus can directly perform numerical analysis on CAD models, avoiding the cumbersome meshing procedure in conventional FEM/BEM and eliminating the difficulty of volume parameterization in isogeometric finite element methods. The advantage of tight integration of CAD and numerical analysis in IGABEM renders it particularly attractive in the application of structural shape optimization because (1) the geometry and the analysis can be interacted, (2) remeshing with shape morphing can be avoided, and (3) an optimized solution returns a CAD geometry directly without postprocessing steps. In the present paper, we apply the IGABEM to structural shape optimization of three dimensional exterior acoustic problems, fully exploiting the strength of IGABEM in addressing infinite domain problems and integrating CAD and numerical analysis. We employ the Burton–Miller formulation to overcome fictitious frequency problems, in which hyper-singular integrals are evaluated explicitly. The gradient-based optimizer is adopted and shape sensitivity analysis is conducted with implicit differentiation methods. The design variables are set to be the positions of control points which directly determine the shape of structures. Finally, numerical examples are provided to verify the algorithm.
The concept of creating all-mechanical soft microrobotic systems has great potential to address outstanding challenges in biomedical applications, and introduce more sustainable and multifunctional products. To this end, magnetic fields and light have been extensively studied as potential energy sources. On the other hand, coupling the response of materials to pressure waves has been overlooked despite the abundant use of acoustics in nature and engineering solutions. In this study, we show that programmed commands can be contained on 3D nanoprinted polymer systems with the introduction of selectively excited air bubbles and rationally designed compliant mechanisms. A repertoire of micromechanical systems is engineered using experimentally validated computational models that consider the effects of primary and secondary pressure fields on entrapped air bubbles and the surrounding fluid. Coupling the dynamics of bubble oscillators reveals rich acoustofluidic interactions that can be programmed in space and time. We prescribe kinematics by harnessing the forces generated through these interactions to deform structural elements, which can be remotely reconfigured on demand with the incorporation of mechanical switches. These basic actuation and analog control modules will serve as the building blocks for the development of a novel class of micromechanical systems powered and programmed by acoustic signals.
Abstract Compared to the traditional synthetic fibrous materials, natural fibres represent sustainable solution to be used either in building construction and noise control engineering and acoustic treatments. Natural fibres are mainly employed in the building industry for their hygrothermal properties, however the possibility to also use them for acoustic purposes would greatly increase their appeal to the market. While synthetic fibres have been studied for almost fifty years, the knowledge of natural fibres is still limited and needs to be expanded. Natural fibres are affected by a large variability of the physical properties, which consequently causes great uncertainty in numerical modelling and difficulties during the design process of acoustics treatments. This study highlights the possibility to enhance the acoustic performance of hemp fibrous materials through the manufacturing process, investigating how each treatments affects the material’s physical characteristics and its sound absorption coefficient. Moreover, a simplified model to evaluate the acoustic performance of hemp fibrous materials as a function of their density is proposed, in order to provide a practical tool to investigate and compare different solutions. The physical parameters numerically evaluated for a varying compression rate have been compared with the experimental results, measured at each stage of the production process on samples with a different density and thickness. The global reliability of the proposed approach is finally investigated by comparing the experimental sound absorption for normal incidence with the results obtained from the Johnson-Champoux-Allard model.
The design of low-frequency sound absorbers with broadband absorption characteristics and optimized dimensions is a pressing research problem in engineering acoustics. In this work, a deep neural network based inverse prediction mechanism is proposed to geometrically design a Helmholtz resonator (HR) based acoustic absorber for low-frequency absorption. Analytically obtained frequency response from electro-acoustic theory is deployed to create the large dataset required for training and testing the deep neural network. The trained convolutional neural network inversely speculates optimum design parameters corresponding to the desired absorption characteristics with high fidelity. To validate, the inverse design procedure is initially implemented on a standard HR based sound absorber model with high accuracy. Thereafter, the inverse design strategy is extended to forecast the optimum geometric parameters of an absorber with complex features, which is realized using HRs and a micro-perforated panel. Subsequently, a quasi-perfect low-frequency acoustic absorber having minimum thickness and broadband characteristics is deduced. Importantly, it is demonstrated that the proposed absorber, comprising four parallel HRs and a microperforated panel, absorbed more than 90% sound in the frequency band of 347–630 Hz. The introduced design process reveals a wide variety of applications in engineering acoustics as it is suitable for tailoring any sound absorber model with desirable features.
Acoustic metamaterial science is an emerging field at the frontier of modern acoustics. It provides a prominent platform for acoustic wave control in subwavelength-sized metadevices or metasystems. However, most of the metamaterials can only work in a narrow frequency band once fabricated, which limits the practical application of acoustic metamaterials. This paper highlights some recent progress in tunable acoustic metamaterials based on various modulation techniques. Acoustic metamaterials have been designed to control the attenuation of acoustic waves, invisibility cloaking, and acoustic wavefront engineering, such as focusing via manipulating the acoustic impedance of metamaterials. The reviewed techniques are promising in extending the novel acoustics response into wider frequency bands, in that tunable acoustic metamaterials may be exploited for unusual applications compared to conventional acoustic devices.
In the historical period, different mosques were built in the Anatolian side; the differences in size, typology and style were affected by the climate conditions, cultural and social aspects, availability of materials and the construction techniques of the region they were built in. The ceiling structure, which is the most influencing factor for mosque acoustics, is designed with either curvilinear elements or a flat ceiling for mosques. In the context of our case study, the eight historical mosques in Turkey, with different materials and types of ceiling structures, are investigated in terms of acoustical characteristics in the main prayer hall. Acoustical data are collected by measurements to reveal how the formal differences and material change in ceiling structures affect the acoustic environments of mosques with similar volume. Distribution of acoustical parameters and the suitability of the values obtained through measurements are compared to reflect the effect of architectural features on the acoustical characteristics of the prayer hall.
The control of acoustic waves have critical applications across many fields, including ocean geology, [1] marine biology, [2] and biomedical engineering. [3] Controlling the direction and dissipation of acoustics waves plays a critical role in noise cancellation [4,5], ultrasonic imaging, [6] and many other applications. Acoustic metamaterials play a significant role in the development of technology used to control acoustic waves. Acoustic metamaterials have interesting properties that interact with incoming pressure waves in unique ways. In particular, these metamaterials are able to exhibit a negative bulk modulus. [7] Contradictory to our natural intuition (nature materials with positive bulk modulus), a negative bulk modulus refers to an increase in volume from an external compressive force [8]. This negative bulk modulus phenomenon occurs at some particular frequency range near monopolar resonance. When acoustic metamaterials are subjected to an oscillating signal near the resonance frequency too fast for the medium to respond in time, a phase shift can be observed. This phase shift impliesπ that the response signal is the negative of the incoming signal. Due to this phase delay, the volume of the metamaterial unit cells responds in a negative manner in respect to the oscillating pressure field, resulting in negative bulk modulus [8]. Similar effects can be observed for mass density subjected to dipolar resonance in which the delay in response causes the center of mass of each unit cell to decelerate when pushed by the oscillating pressure field. In the frequency range where the monopolar and dipolar frequency ranges overlap, the metamaterial exhibits both negative bulk modulus and negative density. The effects of these two negative material properties result in a negative phase velocity with a negative refractive index. Foundational Research