Acoustic Properties Of Materials Research Articles

Development of thermal insulation panels bio-composite containing cardboard and date palm fibers

This study aims to determine the thermal, acoustic, and hygroscopic properties of materials designed for building thermal insulation. These materials are composed of cardboard reinforced with fibers sourced from date palm trees. The composite formulation involves a mixture of 40% date palm components, including pinnate leaves, clusters, trunk petioles, and palm fibers, along with 60% cellulose-based cardboard waste. Water is used as the binding agent, eliminating the need for additional chemicals or additives.For the assessment, thermal conductivity, thermal diffusivity, normal transmission loss (TL), and the acoustic absorption coefficient were measured using the hot plane method, flash method and acoustic impedance tube, respectively. The results indicate that the developed composites have thermal conductivity values ranging from 0.074 to 0.081 W/m.K for a density ranging from 226.6 to 312.8 kg/m³. Additionally, the sound transmission loss coefficients exceed 5 dB in the frequency range of 500–1400 Hz, and the acoustic absorption coefficient is greater than 0.4 across a wide range of frequencies from low to high frequencies (200 Hz–1400 Hz). Furthermore, after 6 h of water immersion, a minimal capillary water absorption coefficient of 203% is achieved. What sets this study apart is the comprehensive life cycle cost analysis performed, shedding light on the sustainability of these materials. The optimization of insulation thickness was also conducted, determining optimal values based on climate conditions and energy sources. Overall, this innovative approach offers environmentally friendly and sustainable insulation options for the construction industry, integrating thermal and acoustic properties, life cycle cost analysis, and insulation thickness optimization.

Stochastic modeling of porous sound absorbing materials using homogenization method and machine learning

This research introduces a novel approach to investigate porous sound absorbing materials using stochastic modeling techniques. The study employs the homogenization method and machine learning to predict the acoustic properties of porous materials. The homogenization method simplifies the analysis of microstructural properties in porous materials, while machine learning is a data analysis technique that utilizes algorithms to learn from data and make predictions. By integrating these methods, this study quantitatively assesses the impact of microscopic structural randomness on sound absorption properties. The study assumes that microstructural parameters are random variables and calculates the sound absorption coefficient through homogenization method. This dataset serves as input for machine learning. A Gaussian process regression model is developed using the dataset to evaluate the distribution of the sound absorption coefficient via the Gauss-Hermite quadrature method. The study implements Bayesian optimization, utilizing the variance of the resulting probability distribution as the acquisition function, to adaptively update the dataset. By iteratively performing these processes, the probability distribution of the sound absorption coefficient can be predicted efficiently and with high accuracy.

Optimal design of fibrous materials for sound absorption

Fibrous materials, which are typical porous materials, play a crucial role in noise control and improving sound quality in the building and automotive industries. Researchers have extensively investigated the acoustic properties of fibrous materials, including both natural and synthetic fibers. Additionally, various numerical and semi-phenomenological models have been employed to accurately predict their acoustic properties. Despite the existence of accurate models, most research on the acoustic properties of fibrous materials has been experiment-oriented. Furthermore, very few studies have focused on reliable and straightforward approaches to optimize these properties and guide the preparation process of fibrous materials. This work aims to develop a robust optimization approach for single-layer and multi-layer fibrous materials by combining numerical optimization methods with numerical and semi-phenomenological acoustic models. The ultimate goal of this optimization approach is to provide designed parameters for fabricating fibrous materials with excellent sound absorption properties. To validate and refine the optimization approach, the fabricated fibrous materials will be thoroughly measured.

Sound speed and attenuation of human pancreas and pancreatic tumors and their influence on focused ultrasound thermal and mechanical therapies.

There is increasing interest in using ultrasound for thermal ablation, histotripsy, and thermal or cavitational enhancement of drug delivery for the treatment of pancreatic cancer. Ultrasonic and thermal modelling conducted as part of the treatment planning process requires acoustic property values for all constituent tissues, but the literature contains no data for the human pancreas. This study presents the first acoustic property measurements of human pancreatic samples and provides examples of how these properties impact a broad range of ultrasound therapies. Data were collected on human pancreatic tissue samples at physiological temperature from 23 consented patients in cooperation with a hospital pathology laboratory. Propagation of ultrasound over the 2.1-4.5MHz frequency range through samples of various thicknesses and pathologies was measured using a set of custom-built ultrasonic calipers, with the data processed to estimate sound speed and attenuation. The results were used in acoustic and thermal simulations to illustrate the impacts on extracorporeal ultrasound therapies for mild hyperthermia, thermal ablation, and histotripsy implemented with a CE-marked clinical system operating at 0.96MHz. The mean sound speed and attenuation coefficient values for human samples were well below the range of values in the literature for non-human pancreata, while the human attenuation power law exponents were substantially higher. The simulated impacts on ultrasound mediated therapies for the pancreas indicated that when using the human data instead of the literature average, there was a 30% reduction in median temperature elevation in the treatment volume for mild hyperthermia and 43% smaller volume within a 60°C contour for thermal ablation, all driven by attenuation. By comparison, impacts on boiling and intrinsic threshold histotripsy were minor, with peak pressures changing by less than 15% (positive) and 1% (negative) as a consequence of the counteracting effects of attenuation and sound speed. This study provides the most complete set of speed of sound and attenuation data available for the human pancreas, and it reiterates the importance of acoustic material properties in the planning and conduct of ultrasound-mediated procedures, particularly thermal therapies.

Acoustic properties of composites materials based on bentonite and coconut or cactus (nopal) fibers

Materials made from natural fibers or waste have been studied to acquire a composite with good acoustical isolation properties, commercial materials used in this concern are polyurethane foam, fiberglass, Rockwool, and drywall. This work proposes using waste coconut and cactus ( Opuntia ficus-indica) fibers to synthesize bentonite composites and study their physicochemical and acoustic properties. Physicochemical properties of precursor and composites (75% wt. fiber) were determined by XRD, FTIR, N2 adsorption, optical, and SEM microscopies. The transmission, reflection, and absorption coefficients, 50 to 10,000 Hz, were obtained in an impedance tube and were compared with commercial materials. The composites were subjected to surface humidity and thermal (30, 50, and 70°C) tests to evaluate the stability of acoustic properties. The mechanical properties of the composites are improved with the addition of bentonite, hardness is increased by 6.7% and 0.9%, and the density is decreased by 73.6% and 45.5%, for coconut and nopal, respectively, porosity also changes. We corroborated the significant presence of montmorillonite in bentonite (XRD), while the nopal or coconut fibers are composed of hemicellulose, cellulose, and lignin (FTIR). Also, mucilage was identified in the nopal samples as adherent biopolymer that generates stability either thermally or in wetting conditions. Coconut fiber has a high absorption coefficient (similar to polyurethane), which is reduced with humidity. However, by adding bentonite, the reflection is more elevated, and transmission is lower than commercial materials. The bentonite and nopal (fiber and composite) presented stability in the acoustic coefficients as a function of humidity and temperature.

Planar Fourier optics for slab waveguides, surface plasmon polaritons, and 2D materials.

Recent experimental work has demonstrated the potential of combining the merits of diffractive and on-chip photonic information processing devices in a single chip by making use of planar (or slab) waveguides. Here, arguments are developed to show that diffraction formulas familiar from 3D Fourier optics can be adapted to 2D under certain mild conditions on the operating speeds of the devices in question. In addition to serving those working in on-chip photonics, this Letter provides analytical tools for the study of surface plasmon polaritons, surface waves, and the optical, acoustic, and crystallographic properties of 2D materials.

Wearable ultrasound bioelectronics for healthcare monitoring

Wearable ultrasound bioelectronics for healthcare monitoring

Three-Dimensional Printing Process for Musical Instruments: Sound Reflection Properties of Polymeric Materials for Enhanced Acoustical Performance.

Acoustical properties of various materials were analyzed in order to determine their potential for the utilization in the three-dimensional printing process of stringed musical instruments. Polylactic acid (PLA), polyethylene terephthalate with glycol modification (PET-G), and acrylonitrile styrene acrylate (ASA) filaments were studied in terms of sound reflection using the transfer function method. In addition, the surface geometry parameters (Sa, Sq, Sz, and Sdr) were measured, and their relation to the acoustic performance of three-dimensional-printed samples was investigated. It was found that a higher layer height, and thus a faster printing process, does not necessarily mean poor acoustical properties. The proposed methodology also proved to be a relatively easy and rapid way to test the acoustic performance of various materials and the effect of three-dimensional printing parameters to test such a combination at the very beginning of the production process.

An experimental transfer matrix method to characterize acoustic materials at high sound pressure levels in airflow environment

A transfer matrix method is proposed for experimental characterization of acoustic materials in the presence of airflow at high sound pressure levels. This method uses two experimental measurements with two different termination loads under flow to derive the transfer matrix coefficients of the tested material. The acoustic pressure and velocity fields upstream and downstream of the material are decomposed into forward and backward traveling waves. Complex models of the wavenumbers are used to account for the damping effect of acoustic waves in the presence of turbulent flow. The components of the transfer matrix of the material are given as function of the pressures and velocities at both faces of the material, which are obtained from the two measurements. The proposed method is validated by comparison with two-source method for different experimental measurements with airflow at high sound pressure levels up to 150 dB and good agreements are obtained. Thus, the proposed method can be used to estimate experimentally the acoustic properties of materials at higher sound pressure excitations in the presence of airflow.

Simulation of Acoustic Properties of Plaster Matrix Composite MATERIAL Reinforced with Corn Stem Fibers

Environmental sustainability and environmental protection are key to shaping the built environment. The use of environmentally sustainable materials in architecture is essential to transform urban centers into modern, sustainable cities, reducing the pollution of air and natural ecosystems, lowering gas emissions, and improving the energy efficiency of structures. In this study, corn processing waste was used as a reinforcing material to create a plaster matrix composite material for use as a sound absorption material. Specimens of two thicknesses were created, and the sound absorption coefficient (SAC) was measured by applying the normal incidence technique. Subsequently, a simulation model for predicting SAC using Artificial Neural Network (ANN) algorithms was utilized to compare the absorption performance of the specimens. The fibers extracted from the corn stem significantly improved the sound absorption performance of the gypsum matrix specimens. This is due to the increase in the porosity of the material caused by the adhesion between the fiber and the plaster which creates air pockets due to the roughness of the fiber. The simulation model appears to be effective in predicting the absorption properties of the material, as indicated by the results.

Thermoacoustic signals generated from pulsed microwave ablation in liver tissue

Microwave-induced thermoacoustic signals are generated when pulsed microwave energy is absorbed by tissue. Thermoacoustic signals contain information about the electromagnetic, thermal, and acoustic material properties of the tissue. Thus, we propose using microwave-induced thermoacoustic signals to monitor microwave ablation, a thermal therapy used to heat and kill malignant tissue, in real-time. Conventional microwave-induced thermoacoustic signals are excited using an external waveguide. Our approach excites thermoacoustic signals via pulsed microwave energy delivered by the already present interstitial microwave ablation antenna. In this talk, we will present the experimental investigation of the evolution of microwave-induced thermoacoustic signals generated during microwave ablation in bovine liver tissue. Pulsed microwave energy was delivered via a narrow-diameter coaxial ablation antenna to simultaneously ablate tissue and excite thermoacoustic signals. Trials were conducted in room-temperature fresh liver tissue as well as room-temperature boiled liver tissue to investigate the influence of ablative temperature rise and tissue coagulation on thermoacoustic signals. Our experimental results show thermoacoustic signal characteristics change throughout the course of microwave ablation that could potentially be used for monitoring the microwave ablation process.

Comparing Acoustic Measurements of Underwater Materials in Pressure Tanks Using a Calibration Panel

Researchers in the United Kingdom and the United States worked together to compare acoustic panel measurement methods and equipment using a calibration test panel. Underwater testing can be used to calibrate various transducers or to measure acoustic properties of materials, from which material properties can then be derived. The calibration panel used in this study consisted of a rubber material. Tests were initially conducted in the Acoustic Pressure Vessel (APV) at the National Physical Laboratory (NPL) in Teddington, UK and were subsequently performed in the Acoustic Pressure Tank Facility (APTF) at the Naval Undersea Warfare Center (NUWC) in Newport, Rhode Island, USA. The UK tank is a smaller-scale version of the US tank. However, the measurement approaches developed by the two groups of researchers differs. The UK utilized a parametric source with a baffle and a planar hydrophone array for reflection and transmission measurements. The US used a spherical source, a linear pseudo-array along with coherent subtraction for reflection, and a single hydrophone for transmission measurements. Early results indicated that the measurement methods showed significant discrepancies, but refurbishment of the US facility and subsequent re-testing of the panel delivered results that were in good agreement between the two groups.

Extended reacting boundary modeling of porous materials with thin coverings for time-domain room acoustic simulations

Modeling of acoustic boundary conditions has a significant impact on the accuracy of room acoustic simulations, which play an important role in the design phase of indoor built environments in order to improve the acoustical comfort. In this work, a numerical framework based on the discontinuous Galerkin (DG) method is presented for modeling extended reacting boundaries of porous absorbers covered by thin materials. The domain decomposition methodology is applied by treating the porous material as a subdomain. Equivalent fluid models are used to depict the acoustic properties of porous materials, whose effective density and compressibility as irrational functions are approximated by multipole rational functions in the frequency domain. By employing the auxiliary differential equation approach to calculate the time convolution, the augmented time-domain governing equations of porous materials can be expressed in the same unified hyperbolic form as the linear acoustic equations, which further enables a consistent upwind numerical flux formulation throughout the whole domain. The numerical coupling across the interface between propagation media is handled by solving the underlying Riemann problem. Compared to existing approaches with the DG method for extended reacting boundaries modeling for room acoustics, the derived upwind numerical flux formulation does not involve the computation of auxiliary variables. The presented framework yield a well-posed linear hyperbolic system with admissible boundary conditions as guided by the “uniform Kreiss condition” (Kreiss, 1970). Acoustic properties of the covering materials are illustrated by considering a limp permeable membrane model. A local time-stepping approach is utilized to improve computational efficiency. Numerical validations against analytical solutions in 1D are performed to verify the desired high-order convergence rate. A 3D case study on modeling spherical wave fronts demonstrates the broadband accuracy of the formulation.

Acoustic Properties Comparison of Ti6Al4V Produced by Conventional Method and AM Technology in the Aspect of Ultrasonic Structural Health Monitoring of Adhesive Joints

The article presents the results of ultrasonic testing of Ti6Al4V material produced by the conventional method and the laser bed fusion method. Modern manufacturing techniques, such as additive manufacturing, allow the production of parts with complex shapes. It is important to control the condition of such components throughout their lifetime. The purpose of this article was to determine the basic acoustic properties of Ti6Al4V material produced by two different methods—bar drawing and the additive manufacturing method. On this basis, an inspection scheme was developed for adhesive joints, the components of which are made by additive manufacturing technology. The decibel drops in the amplitudes of pulses reflected from the boundary of the adhesive-Ti6Al4V-AM and adhesive-Ti6Al4V joints were determined. The decibel drops for the connection of materials made with additive technology are higher than for the material made in a conventional way. The difference in decibel drop in the amplitudes of the additive manufactured material versus the drawn rod, depending on the ultrasonic head, can be up to 60%. The results of the study provide an important practical guideline for testing adhesive joints of parts made with additive manufacturing technology.

Acoustical and heat characterization of recycled fibre reinforced bricks

The present paper reports the acoustical and heat characterization of sheep wool in building units (bricks). In this paper, an attempt is made to rebuild traditional bricks by using wool as a natural admixture to improve heat and sound absorption attributes while also increasing structural strength. Recycling these leftovers creates long lasting building materials while also helping to safeguard the environment. Different specimens of bricks with varying proportions of wool had been prepared and were tested against disparate mechanical properties to highlight the difference between the traditional and adobe (predominantly derived from waste materials) bricks. The processes for specimen preparation and testing are described. Engineers and designers looking for eco- friendly methods should be interested in the utilization of waste materials in the construction sector. It is very crucial to experimentally determine the acoustic properties of building materials due to demand for materials suitable for constructions located in places with high level of noise, typically in urban areas and places close to the areas with heavy traffic researchers who are working to create methodical techniques to assessing, regulating, and analyzing the performance of waste material additives will find it useful. With the increase in quantity of wool, increase in density was observed. The 3.2WB specimen with 3.2% wool had a maximum compressive strength of 70 N/mm2. The property of water absorption gave 13.86% as minimum value of 1WB brick with 1% wool in it. When it comes down to initial rate of absorption of these kind of fiber bricks, it lies between 0.25 to 1.5 kg/m2/min. It drops around 15% of noise coming inside the room. Last, the conclusion part of this review gives an outlook regarding the utilization of the wool fiber by means of theoretical study, efficient and environmentally friendly experiments.

Ultrasound Propagation in Lithium‐Ion Battery Cell Materials: Basis for Developing Monitoring and Imaging Methods

State‐of‐the‐art methods to monitor the degree of wetting of lithium‐ion batteries during production, which are applicable at an industrial scale, are not capable of determining the spatial electrolyte distribution in the porous network of electrodes and separator. Ultrasound can bridge this gap as it has previously been proven to be a suitable method to monitor or evaluate the infiltration of porous structures, for example, epoxy resin in carbon fiber composite. Herein, the acoustic properties of different battery cell materials are evaluated over a wide frequency range in both the dry and wet states, for the first time. Furthermore, a collection of input parameters, from the experimental setup and the evaluation routine to the acoustic parameters of the battery materials themselves, are provided. These parameters are needed for the adaptation of ultrasonic nondestructive testing to the monitoring of the wetting process of a lithium‐ion battery. Most importantly, this work demonstrates that a large change in the sound velocity (up to 100%) is observed when the porous structure of a lithium‐ion battery is filled with electrolyte and thus can serve as an appropriate evaluation figure of merit.

Mechanical, Thermal, and Acoustic Properties of Hemp and Biocomposite Materials: A Review

Bio-based products are paving a promising path towards a greener future and helping win the fight against climate change and global warming mainly caused by fossil fuel consumption. This paper aims at highlighting the acoustic, thermal, and mechanical properties of hemp-based biocomposite materials. Change in sound absorption as a result of hemp fibers and hemp particle reinforcement are discussed in this paper. The thermal properties characterized by the thermal conductivity of the composites are also presented, followed by the mechanical properties and the current issues in biocomposite materials mainly containing hemp as a constituent element. Lastly, the effects of biofillers and biofibers on the various properties of the hemp-composite materials are discussed. This paper highlights the development of and issues in the field of hemp-based composite materials.

Elastic and acoustic properties of anisotropic materials with multiple cracks

Elastic and acoustic properties of anisotropic materials with multiple cracks

Experimental and numerical studies on the acoustic performance of simple cubic structure lattices fabricated by digital light processing

Sound absorption is one of the important properties of porous materials such as foams and lattices. Many mathematical models in the literature are capable of modeling the acoustic properties of lattices. However, appropriate models need to be chosen for specific lattice structures on a case-by-case basis and require significant experience in acoustic modeling. This work aims to provide simplified insights into different mathematical models for the simple cubic lattice. The strut lengths and radii of the unit cells were varied, and the sound absorption properties were measured using an impedance tube. The sound absorption coefficients of the lattices generally increased and exhibited more resonant-like behavior as the strut radius increased. The Delany-Bazley (DB) model and the multi-layered micropore-cavity (MMC) model were used to simulate the acoustic properties of the lattices. The correction factors in the MMC were calculated based on empirical relations fitted using experimental data of the design geometry parameters. Results show that the DB model was able to model the sound absorption coefficients for lattice samples with porosities as low as 0.7, while the MMC with resonator theory is a more appropriate acoustics approach for lattices with porosities lower than 0.7. This work will be highly useful for materials researchers who are studying the acoustic properties of novel porous materials, as well as manufacturers of acoustic materials interested in the additive manufacturing of lattice structures for sound absorption and insulation applications.

Analysis and Research on the Use of Bulk Recycled Materials for Sound Insulation Applications

The application of recycled materials from the automotive industry in the field of the construction industry is a suitable alternative application for these materials and the use of their acoustic and thermal insulation properties. The output of recycling is granular, or chopped materials that can be used as a substitute for conventional materials. One of the important features of building materials is their acoustic properties. The measurement and evaluation of acoustic properties is carried out using an impedance tube as equipment. Measuring compact materials is quite simple and requires the preparation of a sample. Measuring the acoustic properties of granular bulk materials is more complicated and requires the development and production of a special test cartridge. Recycled bulk materials from the automotive industry such as rubber granules and chopped textiles can be applied as fillings for dividing structures. The aim of this paper was to assess the acoustic properties of different fractions of recycled rubber granules and textile chopped material and to compare acoustic properties with compact rubber and textile panels. To evaluate and compare sound absorption coefficient (α) and sound transmission loss (R) parameters, we used basic statistical methods and hypothesis testing methods. The production of compact panels is quite expensive since it is necessary to use special synthetic binders in production, and the content of these substances can also have negative effects on the environment. Based on the results of measuring the acoustic properties of bulk recycled materials and comparing them with compact materials, we can conclude that bulk recycled rubber and textile materials have very good values for their acoustic properties, which enables them to be used in several areas of industry.