Acoustic Materials Research Articles

Research on nonlinear ultrasonic method for evaluating the mechanical properties of 3D printing aluminum alloy

Micro defects, such as pore and inclusions, inevitably appear in the forming process of three-dimensional (3D) printed materials, which would affect the mechanical properties of materials. Therefore, a nondestructive testing method is urgently needed to evaluate the effect of these micro defects on the mechanical properties of materials. In the present work, by using a nonlinear ultrasonic testing technology, mechanical test and characterization of material microstructure, the relationship between the relative acoustic nonlinearity parameter (RANP), tensile strength and material defect ratio of 3D printed aluminum alloy specimens under different scanning powers is investigated. The analysis results show that the greater the material defect ratio is, the smaller the tensile strength is and the greater the RANP is, and the RANP could be used to evaluate the strength of materials. Moreover, fatigue damage induced by high cycle fatigue loading test in the first stage of early performance degradation, the results of nonlinear ultrasonic testing show that the RANP presents an increasing trend as the fatigue load increases. By observing changes in material microstructure, it is found that the increasing acoustic nonlinearity parameter is due to the directional coarsening degree of the precipitated phase increasing, which shows that RANP is very sensitive to the change of material microstructure. The above results show that, the nonlinear ultrasonic testing technology can quantitatively evaluate and predict the mechanical performance and early performance degradation of 3D printing aluminum alloy.

Research on the Performance of Sound Absorption Materials for Substations in Power Grid

As the environmental protection policies become increasingly strict, higher requirements will be proposed for low-frequency noise control problems, and research on control strategies for low-frequency noise in substations is imperative. In this work, principles of resistive acoustic absorption and resonance acoustic absorption materials were analyzed. Based on the measurement in acoustic impedance tubes, the sound absorption performances of two typical sound absorption materials, the glass wool and the micro-perforated panel, were tested. This study offers a new reference for power grid companies to select and combines suitable acoustic materials to realize the optimal application in substations based on noise reduction requirements of different frequencies.

Mitigating low-frequency broadband aircraft noise through a structured assembly of acoustic material and devices

Addressing the challenge of attenuating low-frequency broadband noise emerges as a critical concern within the fields of aeronautics, ground transportation, and construction industries, requires innovative solutions for enhanced acoustic control. Over the last few decades, the literature has seen an increase in low-frequency noise control solutions centered around acoustic metamaterial designs. These proposed technologies exhibit promising acoustic performance, especially proving superior to conventional sound insulation materials in constrained spaces, such as in aerospace applications. Despite the efficacy of typical metamaterials in attenuating tonal noise through narrow resonant frequency maxima, practical applications reveal some challenges, as even slight variations in tonal noise frequencies can compromise the overall effectiveness of such solutions. In response to this, the present paper introduces a novel thin acoustic metamaterial design aimed at improving broadband noise attenuation at low frequencies. This design uses carefully arranged structured metamaterials within a fiberglass layer to create optimal resonance frequency bands for maximum low-frequency noise attenuation. Performance assessment in the low-frequency domain employed COMSOL Multiphysics finite element methods, predicting sound absorption coefficient and transmission loss. Results confirm the effectiveness of the proposed metamaterial design, showcasing broad noise attenuation at low frequencies.

Sound absorption properties of additively manufactured porous materials with minimal surface pore geometries

This study explores the use of additive manufacturing, specifically stereolithography (SLA), to create porous acoustical materials with precise pore geometries for aircraft engine noise reduction. Unlike traditional methods like foaming and fiber-spinning, SLA allows for exact control over pore shapes. Three triply periodic minimal surface (TPMS) pore designs were investigated: split-P, lidinoid, and diamond. These structures were designed through implicit modeling and made from polymeric resin. Their sound absorption capabilities were tested under normal incidence in a two-microphone impedance tube to examine how porosity influences their acoustic performance. Findings revealed unique sound absorption profiles for each geometry, which can be modified by adjusting porosity. Additionally, the static flow resistivity was measured using a raylometer, where results showed that flow resistance is a key factor in their absorption efficiency. Among the three samples, the split-P geometry shows superior sound absorption. This preliminary research highlights the potential of using tailored TPMS geometries in acoustic liners for effective noise control in aerospace applications.

Fundamental acoustics concepts taught through the development of an impedance tube

As part of its mission to educate students, Applied Research Laboratories, The University of Texas at Austin (ARL:UT) employs student technicians to assist on a variety of ongoing research projects. Recently, an undergraduate student technician was tasked with the design and fabrication of a low-cost impedance tube for use in characterizing acoustic materials. To assist the student in developing a set of design requirements, and to determine whether preliminary data were being accurately collected and processed, a set of homework problems were developed to teach the student the fundamental concepts in acoustics necessary for impedance tube development. Homework problems required utilizing both travelling- and standing-wave solutions to the one-dimensional (1D) Helmholtz equation, as well as a basic understanding of the relationships between pressure, particle velocity, and acoustic impedance. Homework solutions were compared with 3D finite element simulations and with experimental data collected using the impedance tube. We felt that these homework problems were effective at conveying basic ideas in acoustics to a student with no prior knowledge in the subject, and how those concepts could be used to solve real-world problems.

Predicting sound transmission loss in particle-reinforced polymer composites using machine learning: A comparative study with experimental and theoretical results

In this study, the use of machine learning (ML) models to predict sound transmission loss (STL) in particle-reinforced polymer composites has been examined. The work included extensive literature research and data extraction for training various ML models, focusing on their effectiveness in accurately predicting STL, which is crucial for evaluating acoustic performance. The method involves processing data and applying it to different ML algorithms, with the models calibrated and tested for reliability. A key aspect is comparing these models' predictions with actual experimental results and theoretical models based on the mass law in acoustics. The findings reveal the potential and limitations of ML in materials science, showing their accuracy in predicting STL and comparing them with traditional theories. This research advances the use of data-driven methods in developing and assessing acoustic materials, significantly impacting materials science and machine learning.

Hydrostatic pressure effects in periodically structured polyurethane acoustic tiles

Traditional underwater acoustic materials commonly make use of periodic air voids to improve their ability to absorb or deflect sound through wave-mode conversion and scattering mechanisms. These air voids have the potential to deform or completely collapse under hydrostatic pressure loading, which may significantly affect the material’s acoustic performance. This study investigates the effects of hydrostatic pressure on the acoustic response of two different types of fabricated polyurethane samples. Developed numerical finite element simulations help identify the main factors associated with the acoustic pressure dependence of such tiles. The results of this work may aid in the development of pressure resistant materials that can better maintain acoustic performance at depth.

A Brief Analysis of The Production of Building Materials Utilizing Waste-Based Reinforcements and Recycled Textiles

The utilization of composite materials in construction has recently exerted a significant impact on society, particularly concerning ecological responsibility and environmental considerations. On a daily basis, proposals advocating the use of emerging materials crafted from discarded or repurposed items are put forth to transcend the limitations posed by conventional resources. One notable aspect of this movement revolves around textile components, encompassing fibres such as wool, cotton, cannabis, and flax. Over the past decade, there has been a heightened focus on worn clothing, as it represents an unprocessed product that holds both commercial viability and ecological benefits. Approximately 1.5 percent of the global waste generated daily comprises textile scraps, with blue jeans, crafted from cotton, standing out as the most prevalent type of apparel worldwide. Textile scraps find new life through recycling, serving various purposes such as the creation of electrical wires, the production of pulverized substances for temperature and acoustic insulation materials, and the incorporation as filler or reinforcement in concrete construction. This paper delves into multiple themes, covering (i) the adverse environmental impacts stemming from the extensive use of clothing; (ii) the recycling and reclamation of textile waste; and (iii) the utilization of waste and reclaimed materials from textiles as building components.

Effect of stacking order on the properties of hybrid palm sheath/polyester fiber felt‐reinforced polymer composite laminates

AbstractNatural fiber‐reinforced composites exhibit excellent mechanical properties. However, achieving a balance between excellent mechanical properties and optimal acoustic performance remains a challenge. In this study, four composite laminates with different stacking orders were fabricated using polyester fiber mats (WFs) and palm sheaths (WPs) through a hot‐press process. Moreover, the effects of different stacking orders on the mechanical and acoustic properties of the composite were investigated. The results revealed that the incorporation of polyester fiber felts and the modification of the layup sequence of WP and polyester fiber felts significantly improved the mechanical and acoustic properties of the composites. Scanning electron microscopy images revealed a strong bonding between palm fibers and polyester fibers at the epoxy resin interface. Compared with pure palm fiber composites, the alternately stacked palm fibers and polyester fibers (WP/WP/WF/WP/WF) exhibited the highest mechanical properties, with a significant enhancement of 142.67% and 16.90% in flexural and tensile strengths, respectively. Additionally, the peak absorption coefficient of polyester fiber felts, positioned in the surface layer of the composite material, within the 2580–3400 Hz frequency band significantly increased from 0.07 to 0.44. Therefore, this study indicates that modifying the stacking order improves the mechanical and acoustic properties of the composites, making them suitable for use in acoustic engineering materials for buildings and decorative panels for furniture, including perforated panels and acoustic screens.Highlights The fabric‐like textured structure significantly enhanced the overall performance of the composites. The stacking order significantly influenced the overall properties of the composite. Alternately stacked polyester fiber felts and palm fibers exhibited excellent mechanical performance. The polyester fiber felts positioned on the surface layer of the composites exhibited superior mechanical performance. A laminate with “green” attributes and good acoustic properties was fabricated.

The future of tire energy: a novel one-end cap structure for sustainable energy harvesting

Piezoelectric energy harvesting is gaining popularity as an eco-friendly solution to harvest energy from tire deformation for tire condition monitoring systems in vehicles. Traditional piezoelectric harvesters, such as cymbal and bridge structures, cannot be used inside tires due to their design limitations. The wider adoption of renewable energy sources into the energy system is increasing rapidly, reflecting a global attraction toward the utilization of sustainable power sources (Aljendy et al. in Int J Power Energy Convers 12(4): 314–337, 2021; Yesner et al. in Evaluation of a novel piezoelectric bridge transducer. In: 2017 Joint IEEE International Symposium on the Applications of Ferroelectric (ISAF)/International Workshop on Acoustic Transduction Materials and Devices (IWATMD)/Piezoresponse Force Microscopy (PFM). IEEE, 2017). The growing interest in capturing energy from tire deformation for Tire Pressure Monitoring Systems (TPMS) aligns with this trend, providing a promising and self-sustaining alternative to traditional battery-powered systems. This study presents a novel one-end cap tire strain piezoelectric energy harvester (TSPEH) that can be used efficiently and reliably inside a tire. The interaction between the tire and energy harvester was analyzed using a decoupled modeling approach, which showed that stress concentration occurred along the edge of the end cap. The TSPEH generated a maximum voltage of 768 V under 2 MPa of load, resulting in an energy output of 32.645 J/rev under 1 MPa. The computational findings of this study were consistent with previous experimental investigations, confirming the reliability of the numerical simulations. The results suggest that the one-end cap structure can be an effective energy harvester inside vehicle tires, providing a valuable solution for utilizing one-end cap structures in high-deformation environments such as vehicle tires.

Effects of Freeze-Drying Processes on the Acoustic Absorption Performance of Sustainable Cellulose Nanocrystal Aerogels.

Cellulose aerogels have great prospects for noise reduction applications due to their sustainable value and superior 3D interconnected porous structures. The drying principle is a crucial factor in the preparation process for developing high-performance aerogels, particularly with respect to achieving high acoustic absorption properties. In this study, multifunctional cellulose nanocrystal (CNC) aerogels were conveniently prepared using two distinct freeze-drying principles: refrigerator conventional freezing (RCF) and liquid nitrogen unidirectional freezing (LnUF). The results indicate that the rapid RCF process resulted in a denser CNC aerogel structure with disordered larger pores, causing a stronger compressive performance (Young's modulus of 40 kPa). On the contrary, the LnUF process constructed ordered structures of CNC aerogels with a lower bulk density (0.03 g/cm3) and smaller apertures, resulting in better thermal stability, higher diffuse reflection across visible light, and especially increased acoustic absorption performance at low-mid frequencies (600-3000 Hz). Moreover, the dissipation mechanism of sound energy in the fabricated CNC aerogels is predicted by a designed porous media model. This work not only paves the way for optimizing the performance of aerogels through structure control, but also provides a new perspective for developing sustainable and efficient acoustic absorptive materials for a wide range of applications.

Nanomaterials for Ultrasound Imaging- Guided Sonodynamic Therapy.

Ultrasound examination is becoming the most popular medical imaging modality because of its low cost and high safety profile. Ultrasound contrast agents enhance the scattering of sound waves, which can improve the clarity and resolution of images. Nanoparticle Ultrasound contrast agents have the characteristics of a large specific surface area and a modifiable surface, which can increase drug loading capacity, prolong circulation time, and enable drug enrichment in specific organs or tissues. This leads to improved therapeutic effects and reducing toxic and side effects. Compared with traditional ultrasound contrast agents, Nano-ultrasound contrast agents overcome the limitation of imaging solely within blood vessels and facilitate imaging within tumor tissues, thereby extending the duration of enhanced imaging. Sonodynamic therapy is an emerging treatment method that has been developed rapidly in recent years, which has the advantages of noninvasive, high spatial and temporal resolution, and low toxicity and side effects. Sonodynamic therapy utilizes a sonosensitizer that, when excited by ultrasound at the tumor site, produces toxic reactive oxygen species, inducing apoptosis or necrosis in tumor cells. Ultrasound-guided sonodynamic therapy allows for real-time observation of lesions, is convenient and flexible, and is free of radiation exposure. With the use of nanomaterials as carriers, ultrasound-guided sonodynamic therapy has made significant strides. This study categorizes and summarizes the current research on acoustic sensitizer carrier materials, including carbon-based, silicon-based, peptide-based, iron-based, metal-organic frameworks, polymers, and liposomes. It concludes by highlighting the current challenges in the integration of ultrasound imaging with sonodynamic therapy and suggests future directions for clinical application development.

Acoustic properties of underwater acoustic metamaterials based on multi-physical field coupling model

In this paper, according to the internal structure of underwater acoustic metamaterial, a multi-physical field coupling model of underwater acoustic metamaterial is established by using finite element analysis. Based on the model, the influence of typical underwater acoustic metamaterial structure and material parameters on sound absorption performance is studied. The results show that increasing the height or radius of the local resonance mass unit in the metamaterial is beneficial to improve the low frequency sound absorption performance. With the increase of the distance between mass elements and the thickness of elastic material, the acoustic absorption performance increases first and then decreases. Increasing the elastic modulus of elastic material of the local resonance unit or matrix will lead to the decrease of low frequency sound absorption performance of the material and the improvement of high frequency sound absorption performance. Increasing the loss factor of elastic material of the local resonance unit or matrix material can broaden the sound absorption band. These rules can provide guidance for the design of underwater acoustic metamaterials.

Stacked space-folded acoustic metasurfaces for the flexible control of sound absorption

Sound absorbing materials capable of working in harsh environments (e.g., fire resistance, moisture resistance, and pressure resistance) while having excellent low-frequency sound absorption properties are highly desirable for many practical applications. Recently, a new class of acoustic absorbers based on space coiling and folding metamaterials (SCFMs) has emerged. The SCFMs could be comprised of rigid plastics, ceramics, and metals and could be a good candidate for developing sound-absorbing devices capable of working in harsh environments. The SCFMs also enable flexible control of low-frequency sound with subwavelength structures, addressing the problem of poor absorption of low-frequency noise encountered by conventional acoustic materials. However, the current geometries of SCFM meta-atoms do not take full advantage of the configuration of three-dimensional space, limiting their ability for flexible control of sound absorption properties. Here, we propose an acoustic absorber based on stacked SCFMs with side openings, which could effectively absorb line-spectrum noise as well as broadband noise. The effects associated with the geometry and resonance modes of SCFMs are shown to significantly influence the sound absorption properties. To understand the sound-metamaterial interaction, an analytical model is obtained to study the acoustic response of SCFMs, which is further validated by numerical simulations. Further experiments have demonstrated the acoustic properties of our proposed metamaterial structure and confirmed the capability of stacked SCFMs for flexible control of the acoustic absorption spectrum. This work provides new possibilities for the development of novel sound absorption metamaterials desirable for many practical applications.

Numerical Equivalent Acoustic Material for Air-Filled Porous Absorption Simulations in Finite Different Time Domain Methods: Design and Comparison

Extracting the microscopic parameters of a porous material is a complex task, and attempts have been made to develop models that can simulate their characteristics, gathering the least amount of information possible. As a case in point, tests to evaluate macroscopic behaviors such as tortuosity, which depends directly on the microscopic fluid velocities, are highly susceptible to generate errors if the precision of the measurement devices is not correct, and the same goes for the other parameters. For this reason, in this paper, a sound propagation model in porous materials with a rigid frame is presented based on a local theory, which tries to simplify, even more, the way to obtain the basic characteristics of porous materials, such as their absorption coefficient at normal and random incidence, and their normal surface impedance. The proposed linearized equivalent fluid model presents four phenomenological coefficients, which characterize acoustic propagation trough the material. Their values are obtained from the material thickness and a measurement in an impedance tube following the ISO 10534 standard. Thus, what is only required is the measured absorption coefficient, either on one third or one octave bands, to fully represent the acoustic behavior in the finite different in time domain (FDTD) method. The model has been simulated with FDTD in porous and fibrous kernels, and the results show a strong agreement with the laboratory measurements and with the analytical results calculated with well-established semi-phenomenological models.

Periodic additive acoustic black holes to absorb vibrations from plates

This paper first suggests a composite structure with periodic additive acoustic black holes (ABH) to absorb vibrations from plates. Different from conventional embedded ABHs, this additive configuration no longer compromises structural integrity. The suggested periodic structure forms a compact acoustic functional material. To analyze the vibration behavior of this coupled structure, we establish a theoretical model employing the Gaussian expansion method (GEM) and the nullspace method (NSM), and it is validated through finite element simulations. Subsequently, we develop a two-dimensional wave and Rayleigh–Ritz method (WRRM) to compute complex dispersion curves, with the imaginary part predicting absorption capability. Our findings reveal that the local resonance eigenmodes of the ABH plate with high loss factors dominate the damping effect, overshadowing the role of Bragg scattering. Furthermore, the introduction of a damping layer proves highly effective in absorbing local vibrations across a wide frequency band. Moreover, we then conduct parametric analyses on various aspects, including ABH order, central thickness, ABH plate thickness, and ABH radius. Notably, the latter two parameters exert a significant influence on damping performance, primarily due to the added mass they introduce. Finally, we examine a finite plate consisting of a 4 × 4 cell arrangement. This composite structure demonstrates substantial modal loss factors when local modes are activated. Moreover, in forced vibration tests, the additive ABHs prove highly effective in mitigating vibrations within the host plate.

Low-frequency broadband sound absorption of the metastructure with extended tube resonators and porous materials

A composite acoustic metastructure consisting of double porous materials and resonators with extended tubes is proposed to seek low-frequency broadband sound absorption, considering the low-frequency absorption of resonators and medium–high frequency absorption of porous materials. Based on the double porosity theory and finite element simulation, the sound absorption performance of the composite metastructure is investigated, and the numerical results are verified by experiments. It has been demonstrated that the metastructure with porous materials arranged vertically or horizontally can exhibit a sound absorption coefficient greater than 0.5 at 265–2000 Hz and greater than 0.8 at 760–2000 Hz, which is significantly superior to the existing sound absorption structure with resonator and porous material with the same thickness. The dependence of the sound absorption performance on the geometric parameters of the extended tubes and the porous materials is revealed. On the premise of keeping the cross-section shape of the extended tube and the arrangement of the porous material unchanged, sound absorption performance at low frequencies depends on the diameter, length, and porosity of the extended tubes, whereas sound absorption performance at medium–high frequencies is primarily determined by the percentage of porous materials. Finally, an improved multiple population genetic algorithm (IMPGA), improved by introducing a weight factor function, is used to optimize the parameters of the composite metastructure in a finite space with a thickness of 50 mm, and the sound absorption coefficient was greater than 0.5 in even lower and broader frequency range of [225,2000] Hz. Additionally, the IMPGA can be adjusted to achieve broadband sound absorption within the target frequency range. It provides a new exploration for acoustic material design for low-frequency broadband sound absorption.

Research of Insertion Loss of Multilayered Construction with Devulcanized Waste Rubber

Abstract In this study, the insertion loss of devulcanized waste rubber baffles were evaluated. Acoustic baffles are suitable to reduce noise from the devices or machines by interfering with their emitting sound waves. Knowledge of the acoustic properties of the material used is of significant importance in ensuring the effectiveness of the acoustic properties of the baffle. Basic properties include airborne sound insulation, which is usually determined during laboratory tests. Baffles consists of sound absorbing and sound insulating materials. In this study, plasterboards were used as sound insulating material and devulcanized waste rubber as sound absorbing material. During the devulcanization process, porous granules are obtained, which can be used as an acoustic material. In this study, two types of rubber granules were devulcanized by grinding method and one other type was chemically devulcanized. Three types of rubber granules were mixed together in increasing 25 % proportion steps and glued with patented polyurethane glue. A total of 15 different composition devulcanized waste rubber granule boards were made. Rubber boards were attached together with the plasterboards. Insertion loss of the different composite baffles was measured in semi-anechoic chamber in a purposefully designed stand in 1/3rd octave bands. The results showed that the insertion loss of the baffles was mostly dependent on the rubber granule board density. When the density of the rubber board increased, the insertion loss also increased. The 5–6 dB insertion loss difference was measured between the most and least dense rubber granule board baffles.

Acoustic Materials in Automobiles

Automobile comfort and design has had an important impact on the world wide economy during the past century and millions of additional vehicles have been sold because of it. Much research work is being done on automobile interior design in comparison to other industrial designs. However, sound level inside the cabins affects the journey of millions of passengers to a great degree and comfort than many other subjects. Low noise level in the cabins is a comfort parameter of high importance. Therefore an attempt has been made in this paper to review the different acoustic materials being used in various automobiles and also their properties which have impact on noise reduction

Abaca Fiber as a Potential Reinforcer for Acoustic Absorption Material at Middle-High Frequencies

Abaca Fiber as a Potential Reinforcer for Acoustic Absorption Material at Middle-High Frequencies