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        <title>Frontiers in Acoustics | New and Recent Articles</title>
        <link>https://www.frontiersin.org/journals/acoustics</link>
        <description>RSS Feed for Frontiers in Acoustics | New and Recent Articles</description>
        <language>en-us</language>
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        <pubDate>2026-04-12T00:52:50.388+00:00</pubDate>
        <ttl>60</ttl>
        <item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2026.1802446</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2026.1802446</link>
        <title><![CDATA[Editorial: perception-driven acoustic engineering]]></title>
        <pubdate>2026-02-16T00:00:00Z</pubdate>
        <category>Editorial</category>
        <author>Antonio J. Torija</author><author>Siddhartha Krishnamurthy</author><author>Roberto Merino-Martinez</author>
        <description></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1653659</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1653659</link>
        <title><![CDATA[Modeling elastic wave mode conversion within zero-phase-difference ultrathin anisotropic medium]]></title>
        <pubdate>2026-01-07T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Xinyue Bi</author><author>Yucheng Gao</author>
        <description><![CDATA[We investigate a novel mechanism for elastic wave mode conversion in structured media composed of periodic resonant scatterers. Traditional models typically rely on phase accumulation between longitudinal and transverse wave components as they propagate through an anisotropic layer. This limits their effectiveness in the low-frequency or thin-layer regime. In contrast, we propose a new model based on oblique resonance within a homogenized anisotropic block, which generates oblique displacements and introduces tangential motion at the interface. It is carried out under the limiting condition where the scatterer thickness approaches zero. Previous studies did not consider this zero-thickness limit. If one directly substitutes d = 0 into their formulations, the result becomes a trivial solution.This fundamentally differs from existing literature that derive methods for finite-thickness structures. We derive the boundary conditions and establish a coupled system of equations to describe the transmission and reflection behavior. Effective parameters, including mass density and impedance, are extracted from field quantities within the computational region and are shown to be angle-dependent. The conversion rates predicted by our model show excellent agreement with simulations, confirming both the physical assumptions and the analytical formulation. The proposed approach provides a new pathway for low-frequency, compact, and efficient control of elastic wave modes.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1621355</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1621355</link>
        <title><![CDATA[Developing a Sound, Noise and Health Conceptual Framework for fair and equitable dispersion of aircraft]]></title>
        <pubdate>2025-11-25T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Lisa R. Lavia</author><author>Charlotte Clark</author><author>Antonio J. Torija</author>
        <description><![CDATA[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.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1615210</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1615210</link>
        <title><![CDATA[The acoustic Dirac equation as a model of topological insulators]]></title>
        <pubdate>2025-09-29T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Abhirup Basu</author><author>Keith Runge</author><author>Pierre A. Deymier</author>
        <description><![CDATA[The dynamical equations of motion for a discrete, one-dimensional harmonic chain with side restoring forces are analogous to the relativistic Klein–Gordon equation. Dirac factorization of the discrete Klein–Gordon equation introduces two equations with time reversal (T) and parity (P) symmetry-breaking conditions. The Dirac-factored equations enable the exploration of the properties of the solutions of the dynamic equations under PT symmetry-breaking conditions. The spinor solutions of the Dirac factored equations describe two types of acoustic waves: one with a conventional topology (Berry phase equal to 0) and the other with a non-conventional topology (Berry phase of π). In the latter case, the acoustic wave is isomorphic to the quantum spin of an electron, also known as an “acoustic pseudospin,” which requires a closed path, corresponding to two Brillouin zones (BZs), to restore the original spinor. We also investigate the topology of evanescent waves supported by the Dirac-factored equations. The interface between topologically conventional and non-conventional chains exhibits topological surface states. The Dirac-factored equations of motion of the one-dimensional harmonic chain with side springs can serve as a model for the investigation of the properties of acoustic topological insulators.]]></description>
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        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1616297</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1616297</link>
        <title><![CDATA[Enhancing tumoricidal effects of radiation therapy with low-intensity focused ultrasound in murine breast cancers]]></title>
        <pubdate>2025-09-02T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Michelle Marie Schumacher</author><author>Claudia Gutierrez Chavez</author><author>Beata Malachowska</author><author>Sanjay Pandey</author><author>Tatyana Tchaikovskaya</author><author>Saurabh Singh</author><author>Steve Barry</author><author>Rodney Macedo</author><author>Chandan Guha</author>
        <description><![CDATA[IntroductionFocal cancer therapies fail to cure metastatic disease. Our prior studies indicated that Low Intensity Focused Ultrasound (LOFU) boosts antitumoral immunity in murine melanoma and prostate cancer. We hypothesized that LOFU, combined with radiation therapy (RT), could stimulate an immunogenic tumor microenvironment (TME) in murine breast cancers, potentially acting as an in-situ vaccine.MethodsWe evaluated LOFU ± RT in TSA and E0771 breast cancer models in BALB/c and C57BL/6 mice, respectively, and measured intra-tumoral temperatures and gene expression to assess acoustic thermal stress using quantitative RT-PCR.ResultsFlow cytometry and gene expression showed that LOFU induced unfolded protein response pathway and heat shock protein RNA. LOFU modified the immune contexture in the TME of both tumor models, notably by increasing CD8+ T cell infiltration, including anti-gp70 CD8+ T cells, and reducing the RT-induced regulatory T cell response in TSA tumors.DiscussionLOFU, as a non-ablative therapeutic, primes the TME and augments control of murine breast cancers by inducing tumor-specific adaptive immune responses.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1620233</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1620233</link>
        <title><![CDATA[Compensated orthogonal spread codes for full parallel usage of multi-transducer ultrasonic testing systems in NDE]]></title>
        <pubdate>2025-08-29T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Marius W. Schäfer</author><author>Giovanni Del Galdo</author><author>Sarah C. L. Fischer</author>
        <description><![CDATA[IntroductionThe use of multi-transducer methods and equipment is common in non- destructive testing. These systems and methods provide increased accuracy or even enable test cases that cannot be carried out with single transducer testing. On the downside, these systems significantly increase execution time when the evaluation of a single channel or evaluation of crosstalk to other channels is performed sequentially. As the number of individual channels increases, so does the execution time and the amount of data. This paper presents the theoretical integration and experimental validation of orthogonal spread code sequences for multi-transducer ultrasonic testing.MethodsThe custom-built, two-channel ultrasonic test system and the measurement setup using a 60 mm-wide rectangular specimen are shown. The cross-correlation properties of random binary, random Gaussian and Gold codes, known from GPS, are compared for the code selection.ResultsThe Gold codes, the most promising set of codes, are experimentally investigated for suitability. Based on the results, upscaling potential of the method is presented based on a simulation using 9 code sequences summed with a random offset to a single array to replicate a 9-transducer setup. After compensating for the transfer function of the ultrasonic testing system, a localisation accuracy of less than 4 ns is achieved using a polynomial fit and a sampling interval of 8 ns.DiscussionBy incorporating this method into ultrasonic testing, measurement speed can be increased while stability and accuracy are improved.While codes with an amplitude close to the cross-correlation ratio will be difficult to detect, this method can be extended beyond 9 transducers for higher amplitudes, as long as the total amplitude does not exceed the maximum voltage limit of the electronic system.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1624669</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1624669</link>
        <title><![CDATA[Human response to eVTOL drone sound: an online listening experiment exploring the effects of operational and contextual factors]]></title>
        <pubdate>2025-08-28T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>James Woodcock</author><author>Adam Thomas</author><author>David Hiller</author><author>Ana Luisa Pereira Maldonado</author><author>Laura McLeod</author><author>Calum Sharp</author><author>Fiona Smith</author>
        <description><![CDATA[IntroductionProject CAELUS is developing the United Kingdom's first national distribution network using drones to transport vital medical supplies throughout Scotland. Noise is a major barrier to public acceptance of drone networks, yet empirical data on the human response to drones used in a medical delivery context remains limited. This study addresses that gap by investigating the annoyance response to sounds from the eVTOL medical delivery drone used in Project CAELUS.MethodsAn online listening experiment was conducted to assess annoyance related to overflight (N – 425) and take-off (N – 278) operations. The experiment examined the effects of listener–drone distance, ambient soundscape (remote rural, rural village, urban), and contextual framing (medical delivery vs. no context) on annoyance. Data were analysed using aligned rank transform ANOVAs to test for main effects and interactions for each factor.ResultsAligned rank transform ANOVAs revealed significant effects of listener–drone distance, ambient soundscape, and contextual framing on annoyance (p < 0.01 for all three factors). Annoyance decreased with increasing distance from the drone and was higher in quieter ambient soundscapes. Providing contextual information about the medical use of the drone significantly reduced annoyance.DiscussionFindings indicate that both acoustic and non-acoustic factors influence perceived annoyance from drone operations. In particular, contextual information about medical use reduced annoyance, suggesting that effective community engagement may improve public acceptance of drone networks.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1616806</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1616806</link>
        <title><![CDATA[Study on the noise reduction effect of sound barriers on the aerodynamic noise of high-speed trains]]></title>
        <pubdate>2025-07-07T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Rui Zhang</author><author>Hui Li</author><author>Junquan Yang</author><author>Xiaoxiong Chen</author><author>Shengyou Yang</author>
        <description><![CDATA[In recent years, the continuous increase in the speed of high-speed trains has led to growing concern about noise generated by train operations. Currently, three types of sound barriers are commonly used: fully enclosed, semi-enclosed, and vertical. The effectiveness of noise reduction due to complex aerodynamics in higher-speed trains remains unclear and requires further research. This article employs ANSYS Fluent fluid software to establish a full-scale three-dimensional numerical model that simulates the wind tunnel test of a train traveling at a speed of 350 km/h. The noise distribution in the section with the largest noise source is analyzed in COMSOL using the method of line sound source comparison. Additionally, we investigate the noise reduction efficiency of various types and sealing degrees of sound barriers concerning aerodynamic noise. The results indicate that the fully enclosed sound barrier provides the best noise reduction across all frequency ranges, followed by the vertical sound barrier, which offers the second-best noise reduction effect. For high-frequency noise, a higher sealing degree of the sound barrier correlates with improved noise reduction. In highly sensitive areas, priority should be given to fully enclosed sound barriers, followed by vertical sound barriers.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1568083</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1568083</link>
        <title><![CDATA[Measurement of dynamic electrokinetic effects at the glass/electrolyte interface using a mega-Hertz-level mechanical wave]]></title>
        <pubdate>2025-06-05T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Sudeepthi Aremanda</author><author>Yifan Li</author><author>Gideon Onuh</author><author>Ofer Manor</author>
        <description><![CDATA[We measured the dynamic electrical properties of a spontaneously charged glass surface in an electrolyte solution by using a MHz-level surface acoustic wave (SAW) actuator to introduce a same-frequency mechanical wave into the glass substrate. The mechanical wave vibrated ions in the nanometer-thick electrical double layer (EDL) to appear at the glass/electrolyte interface. The out-of-equilibrium EDL leaked an electrical field, which was modulated by ion vibration frequency to reveal the presence of ions and their dynamic motion. A previous study excited EDLs on the piezoelectric lithium niobate substrate of a SAW actuator in contact with an electrolyte solution, but it remained unclear whether the mechanical or electrical components of the SAW in the piezoelectric substrate dominated the EDL excitation. Here, we isolated the SAW mechanical component in glass and showed that it introduces a similar ion electrokinetic vibration in the excited EDL at the glass/electrolyte interface using sodium nitrate and potassium chloride solutions as electrolytes. The measured electrical field leakage spectra were of similar magnitude to those measured in the previous study and exhibited similar non-monotonic behaviors, taking local maxima where the SAW period (the inverse of its frequency) was synchronized with the ion relaxation times in the EDL. At these frequencies, the synchronization maximized ion vibration displacement, thereby amplifying the electrical field leakage. Our findings may be used to study the electrokinetic properties of solid surfaces and ion dynamics in EDLs. Moreover, SAW-actuated fluidic platforms may support out-of-equilibrium EDLs relevant to ion-selective membranes and the film stability of electrolyte solutions.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1543456</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1543456</link>
        <title><![CDATA[Characterizations of acoustical porous media: standardized methods, current trends and challenges]]></title>
        <pubdate>2025-05-08T00:00:00Z</pubdate>
        <category>Review</category>
        <author>Luc Jaouen</author><author>François-Xavier Bécot</author><author>Fabien Chevillotte</author>
        <description><![CDATA[Understanding and predicting the vibro-acoustic behavior of acoustical porous materials (like foams, synthetic or natural fibers, metamaterials...) requires to determine the parameters of their solid and their fluid phases. This work presents an non-exhaustive overview of the methods commonly used to assess the visco-elastic and acoustic parameters of such acoustic porous media. A first part is dedicated to identify the parameters related to the dissipation in the fluid phase while a second part focuses on the identification of the parameters related to the solid phase (also called the skeleton). The perspectives related to the characterization of acoustical porous media are also depicted, particularly in the context of recent and ongoing standardization developments.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1545057</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1545057</link>
        <title><![CDATA[Characterizing random complex biological media by quantifying ultrasound multiple scattering]]></title>
        <pubdate>2025-04-09T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Omid Yousefian</author><author>Azadeh Dashti</author><author>Haley Geithner</author><author>Yasamin Karbalaeisadegh</author><author>Shanshan Yao</author><author>John Blackwell</author><author>Mir Ali</author><author>Stephanie Montgomery</author><author>Yong Zhu</author><author>Thomas Egan</author><author>Marie Muller</author>
        <description><![CDATA[Introduction: In this in silico, in vitro, and in vivo study, we propose metrics for the characterization of highly scattering media using backscattered acoustic waves in the MHz range, for application to the characterization of biological media.Methods: Multi-element array transducers are used to record the ultrasonic Inter element Response Matrix (IRM) of scattering phantoms and of lung tissue in rodent models of pulmonary fibrosis. The distribution of singular values of the IRM in the frequency domain is then studied to quantify the multiple scattering contribution. Numerical models of scattering media, as well as gelatin-glass bead and polydimethylsiloxane phantoms with different scatterer densities, are used as a first step to demonstrate the proof of concept.Results: The results show that changes in microstructure of a complex random medium affect parameters associated with the distribution of singular values. Two metrics are proposed: E(X), which is the expected value of the singular value distribution, and λmax, the maximum value of the probability density function of the singular value distribution, i.e., the most represented singular value. After validation of the methods in silico and in phantoms, we show that these metrics are relevant to evaluate pulmonary fibrosis in an in vivo rodent study on six control rats and eighteen rats with varying degrees of severity of pulmonary fibrosis. In rats, a moderate correlation was found between the severity of pulmonary fibrosis and metrics E(X) and λmax.Discussion: These results suggest that such parameters could be used as metrics to estimate the amount of multiple scattering in highly heterogeneous media, and that these parameters could contribute to the evaluation of structural changes in lung microstructure.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1529474</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1529474</link>
        <title><![CDATA[Inverse design of topological diatomic lattices based on complex phase locus]]></title>
        <pubdate>2025-04-02T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Hasan B. Al Ba’ba’a</author><author>Jihong A. Ma</author>
        <description><![CDATA[Topological phononics and acoustics have recently garnered significant attention due to their promise of a wide range of advanced wave-controlling applications, including mechanical computing, energy harvesting, and noise isolation. Topological states are vibrational modes emerging inside frequency bandgaps, and typically follow the bulk-boundary correspondence, meaning that the topological features observed at boundaries are determined by the bulk properties—the unit cell. Traditionally, topological states are characterized by analyzing the eigenvectors of the effective Hamiltonian of a given unit cell. However, this approach presents challenges when a rapid and accurate design is needed to achieve desirable topological characteristics as it often involves trial and error to obtain the ideal unit cell parameters. In this study, we propose a rigorous methodology to inversely design one-dimensional diatomic lattices based on the topological properties of complex phase loci, derived from the off-diagonal elements of the effective Hamiltonian. We discuss three representative shapes of complex phase loci: ellipse, epitrochoid, and hypotrochoid. Our methodology can be further expanded to higher dimensions, enabling more complex geometric designs for versatile topological phononic and acoustic features.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2025.1544464</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2025.1544464</link>
        <title><![CDATA[Sorting droplets beyond the Rayleigh limit under acoustic-gravity forces: a theoretical approach]]></title>
        <pubdate>2025-03-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Jeyapradhap Thirisangu</author><author>Karthick Subramani</author>
        <description><![CDATA[The physics of droplets beyond the Rayleigh limit offers a novel acoustic sorting method that is fundamentally different from the techniques applied to sort droplets within the Rayleigh limit. Using this “acoustic sorting beyond Rayleigh limit” method, we theoretically demonstrate that by controlling the frequency (f) and acoustic energy density (Eac), smaller droplets can be suspended while larger ones settle against gravity, or larger droplets can be suspended while smaller ones settle. Intriguingly, this method also enables the suspension of intermediate-sized droplets, allowing both smaller and larger droplets to settle simultaneously. Furthermore, acoustic sorting is demonstrated for droplets of identical size but with varying interfacial tensions.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1498722</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1498722</link>
        <title><![CDATA[Multi-objective optimization of structured material parameters for reducing broadband aircraft noise across various frequencies]]></title>
        <pubdate>2025-01-06T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Tenon Charly Kone</author><author>Sebastian Ghinet</author><author>Raymond Panneton</author><author>Anant Grewal</author>
        <description><![CDATA[IntroductionControlling broadband noise across the entire frequency spectrum, from low to high frequencies, remains a critical challenge in aerospace, transportation, and construction industries. Current acoustic metamaterials are effective primarily for low-frequency noise but suffer from narrow-band resonances that limit their application for broader-band noise attenuation.MethodsThis study introduces an innovative structured material system comprising a parallel assembly of structured materials and Helmholtz Resonators embedded within a fiberglass layer. A multi-objective optimization approach based on a surrogate model was employed to fine-tune the parameters of each structured material. The optimization process allowed precise grouping of individual resonant frequencies, thereby broadening the effective resonance frequency band to address low- and high-frequency noise.ResultsThe proposed structured material system demonstrated significant broadband noise attenuation across a wide frequency range. The optimized configuration achieved effective noise reduction while adhering to practical implementation constraints, providing a feasible solution for industrial applications.DiscussionThis study underscores the importance of optimization in advancing noise control technologies. By overcoming the limitations of narrow-band resonances, the proposed approach achieves effective broadband noise attenuation, addressing critical challenges in aerospace, transportation, and construction. The integration of structured materials and Helmholtz Resonators, optimized using a surrogate model, broadens the resonance frequency band while meeting practical implementation requirements. These results highlight a viable and impactful solution for noise control across diverse industries.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1512579</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1512579</link>
        <title><![CDATA[Direct observation of small scale capillary wave turbulence using high speed digital holographic microscopy]]></title>
        <pubdate>2024-12-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>William Connacher</author><author>Jeremy Orosco</author><author>Oliver T. Schmidt</author><author>James Friend</author>
        <description><![CDATA[IntroductionIt is now known that capillary waves driven upon a fluid interface by high frequency (>1 MHz) ultrasound exhibit capillary wave turbulence: the appearance of waves with phase and wavelength far removed from the excitation signal that drives them. These waves are responsible in significant part for atomization, a useful application for ultrasound, though the physics responsible for their appearance is poorly understood.MethodsWe use high-speed digital holographic microscopy to observe these capillary waves, an important step towards understanding their generation and atomization phenomena.ResultsWe observe Zakharov-Kolmogorov weak wave turbulence for a limited range of input power, and find broader turbulence phenomena outside this range. We see discrete thresholds as the input power is increased, where higher and higher frequency responses are driven in the capillary waves with sudden onset between regimes.DiscussionWe employed spatial analysis to find extensions of the capillary wave response to higher frequencies, suggesting there is additional information in the spatial distribution of the capillary wave that is rarely if ever measured. We verified via frequency modulation that nonlinear resonance broadening is present, which undermines the use of Faraday wave or parametric wave theories to characterize these waves, important in the context of atomization which is now, definitively, not a Faraday wave process.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1485372</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1485372</link>
        <title><![CDATA[Efficient Snell’s law solution for generating robust acoustic tweezers in dual-layered media]]></title>
        <pubdate>2024-12-02T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Huy Q. Pham</author><author>Nhung Nguyen</author><author>Quang Tran</author><author>Trung B. Le</author><author>Trung Q. Le</author>
        <description><![CDATA[Acoustic tweezers can trap and manipulate a target along a desired path without physical contact. Potential applications of this technology may require the propagation of acoustic waves through non-homogeneous media. It is typically assumed that the acoustic impedance of media is the same. However, this assumption leads to reduced efficiency in both the trapping accuracy and strength of the acoustic tweezers. In this study, we propose a method to derive phases driving an 8x8 array of ultrasonic transducers using generalized Snell’s law to account for the variation in the speed of sound between media layers of planar or non-planar interfaces. The results indicate that the tweezers formed with our approach maintain their patterns and trapping capability at selected trapping locations. In addition, our method significantly enhances the trapping accuracy and force, achieving up to ten times greater force and more accurate alignment with the selected trapping points compared to the previous method that assumes a uniform speed of sound.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1502136</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1502136</link>
        <title><![CDATA[Detaching cells in culture medium using forced vibration for removing a centrifugation from culture process]]></title>
        <pubdate>2024-11-29T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Hayato Shimoguchi</author><author>Chikahiro Imashiro</author><author>Kenjiro Takemura</author>
        <description><![CDATA[Recent advancements in cell culture have significantly impacted various fields, including drug discovery and regenerative medicine. Consequently, there is an increasing need to minimize the contamination risks and labor involved in cell culture processes. Traditional cell detachment methods typically employ proteolytic enzymes followed by centrifugation to remove these enzymes after cell detachment. This process often requires numerous manual interventions which can lead to potential contamination and deterioration of cell quality. In this study, we propose a novel cell detachment method that eliminates the need for centrifugation even with less trypsinization time. Our approach involves reducing the duration of trypsinization, collecting the trypsin before complete cell detachment, and subsequently detaching the cells using forced vibration within the culture medium. We conducted experiments to optimize the enzyme treatment time and vibration conditions. Our results demonstrated that this method achieved an 82.8% detachment rate of cells from the culture surface. These findings indicate that the proposed cell detachment technique is effective in removing cells from the culture substrate and the following subculture process without the need for centrifugation.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1483731</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1483731</link>
        <title><![CDATA[A meta-analysis of the effect of ultrasound activation parameters on phase-change nanodroplets in imaging and therapy]]></title>
        <pubdate>2024-11-19T00:00:00Z</pubdate>
        <category>Review</category>
        <author>Maryam Dorvashi</author><author>Owen J. Harrison</author><author>Hossam H. Sultan</author><author>Ge Zhang</author><author>Maya Thanou</author><author>Navid Ghavami</author><author>Gianluigi Tiberi</author><author>Mohammad Ghavami</author><author>Sevan Harput</author>
        <description><![CDATA[Phase-change nanodroplets (PCNDs) have been used in ultrasound imaging, targeted drug delivery, blood-brain-barrier (BBB) opening, sonothrombolysis and histotripsy for over a decade. For these ultrasound applications, PCNDs provide higher in vivo lifetime than microbubbles (MBs), the potential for extravasation inside tumour and on demand activation, which is the transition of the liquid-core of nanodroplets to gaseous microbubbles through acoustic droplet vaporisation (ADV). Operating above the ADV threshold can offer repeatable activation of PCNDs and the subsequent oscillation of acoustically activated PCNDs, which is advantageous in imaging and therapeutic applications. Efficient and repeatable activation of PCNDs require a good understanding of ultrasound parameters and nanodroplet composition for different biomedical applications. Therefore, this article presents a meta-analysis of the effect of ultrasound activation parameters on ADV for various PCNDs in different biomedical applications. About 7,500 articles were considered for this study, but only 45 articles were chosen and evaluated in the meta-analysis based on the following criteria: 1): activation parameters, including ultrasound frequency, peak negative pressure, transmit pulse length or duration have been clearly mentioned, 2), droplets range in nanometre size (<1 µm), 3), experiments are performed at a temperature of 37°C and 4) ADV threshold has been clearly mentioned and observations are not due to inertial cavitation (IC). From selected publications, we recorded the activation frequency (0.06–16 MHz), ultrasound pressure (0.18–14.9 MPa), activation pulse length (µs-ms range) and nanodroplet size for different types of perfluorocarbon PCNDs (C3F8, C4F10, C5F12 and C6F14) and evaluated the relation of these parameters to each other. Finally, a Root Mean Square (RMS)-like power metric, which is a combination of ultrasound peak negative pressure and square root of ultrasound pulse length, is proposed for identifying the ADV threshold behaviour instead of using pressure or mechanical index values.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1489401</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1489401</link>
        <title><![CDATA[Subwavelength topological interface modes in a multilayered vibroacoustic metamaterial]]></title>
        <pubdate>2024-11-11T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Majdi O. Gzal</author><author>Joshua R. Tempelman</author><author>Kathryn H. Matlack</author><author>Alexander F. Vakakis</author>
        <description><![CDATA[We present a systematic and rigorous analytical approach, based on the transfer matrix methodology, to study the existence, evolution, and robustness of subwavelength topological interface states in practical multilayered vibroacoustic phononic lattices. These lattices, composed of membrane-air cavity unit cells, exhibit complex band structures with various bandgaps, including Bragg, band-splitting induced, local resonance, and plasma bandgaps. Focusing on the challenging low-frequency range and assuming axisymmetric modes, we show that topological interface states are confined to Bragg-like band-splitting induced bandgaps. Unlike the Su-Schrieffer-Heeger model, the vibroacoustic lattice exhibits diverse topological phase transitions across infinite bands, enabling broadband, multi-frequency vibroacoustics in the subwavelength regime. We establish three criteria for the existence of these states: the Zak phase, surface impedance, and a new reflection coefficient concept, all derived from transfer matrix components. Notably, we provide an explicit expression for the exact location of topological interface states within the band structure, offering insight for their predictive implementation. We confirm the robustness of these states against structural variations and identify delocalization as bandgaps narrow. Our work provides a complete and exact analytical characterization of topological interface states, demonstrating the effectiveness of the transfer matrix method. Beyond its analytical depth, our approach provides a useful framework and design tool for topological phononic lattices, advancing applications such as efficient sound filters, waveguides, noise control, and acoustic sensors in the subwavelength regime. Its versatility extends beyond the vibroacoustic systems, encompassing a broader range of phononic and photonic crystals with repetitive inversion-symmetric unit cells.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/facou.2024.1478414</guid>
        <link>https://www.frontiersin.org/articles/10.3389/facou.2024.1478414</link>
        <title><![CDATA[Optimization of sound absorption of recycled Nylon fibrous materials]]></title>
        <pubdate>2024-11-08T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Julien Biboud</author><author>Saïd Elkoun</author><author>Raymond Panneton</author>
        <description><![CDATA[A semi-empirical model for the assessment and an optimization procedure of the sound absorption coefficient of compressed nonwoven fibrous materials made from recycled Nylon fibers (RNF) is developed. In general, the prediction of the sound absorption properties of materials requires the measurement of non-acoustic parameters by specialized characterization tools that are not always within reach of most laboratories. The objective of the proposed model is to establish empirical relationships between these non-acoustic parameters and the bulk density of RNF materials. These empirical relationships are then substituted into a conventional acoustic model for porous materials, namely, the model of Johnson-Champoux-Allard. The proposed model accurately predicts the sound absorption coefficients of compressed RNF materials based solely on bulk density, thickness, and frequency. This prediction is validated through impedance tube measurements. Moreover, the model is used with a proposed optimization producedure to identify the ideal density and thickness for maximum sound absorption at a specific frequency. Impedance tube measurements on optimized configurations confirm the effectiveness of this optimization process.]]></description>
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