Acoustic Properties Of Materials Research Articles

Investigating the Sound Absorption Properties of Silk Cotton and Other Sound-Absorbent Materials

This research investigates the acoustic properties of various materials to mitigate sound transmission and enhance acoustic environments, focusing on silk cotton, cotton wool, chipped foam, and open-cell polyurethane foam. The study evaluates these materials for sound absorption and reduction, considering sound frequency and material density. Materials were tested for their sound reduction and absorption coefficients, with silk cotton emerging as the most effective across a broad frequency spectrum, particularly below 200 Hz and above 1000 Hz. The research demonstrated that silk cotton, with its high porosity and fine fibre structure, achieved significant sound reduction even at low densities The findings align with theoretical predictions of resonance frequencies, showing a strong correlation (r2 = 0.9988 for the sound box and r2 = 0.9894 for the sound pipe). Sound intensity and sound pressure levels were measured using a sound level meter, and data analysis was conducted using graphing and calculating software. The researcher employed modified laboratory methods to account for loose materials and equipment limitations, validating the use of theoretical equations to estimate sound absorption and reduction properties The study provides some insights into using fibrous materials like silk cotton for noise reduction and acoustic enhancement. These findings have practical implications for improving sound quality in various environments, such as schools, studios, and public spaces, contributing to noise reduction strategies and enhancing auditory experiences.

Modelling the Acoustic Properties of Baffles Made of Porous and Fibrous Materials

The research described in the article addresses the problem of measurement, prediction and practical use of the acoustic properties of materials determined in an impedance tube. The aim of the research was to develop a simple calculation model for the insertion loss of small machinery enclosures, based on the normal incidence sound transmission loss and the normal incidence sound absorption coefficient of porous and fibrous materials. Both experimental and model tests were carried out on materials such as mineral wool, melamine foam and rebonded polyurethane foam. Assessing the absorption properties of the tested porous and fibrous materials was performed using selected theoretical models, relating the calculations of the normal incidence sound absorption coefficient to measurements of this parameter conducted using an impedance tube. The application of the modified Allard and Champoux model brought the best results with the smallest discrepancies of the obtained results in relation to the experimental tests. Assessing the sound-insulating properties of the tested mineral wool was carried out using the proposed calculation model for the normal incidence sound transmission loss, relating the obtained results to measurements conducted using an impedance tube. The assessment of the sound-insulating properties of porous and fibrous materials was performed using the proposed calculation model for insertion loss, which was validated using two prototype test stands for determining the insertion loss of cubic enclosures, in this case with walls made of porous and fibrous materials. Satisfactory results were obtained for engineering applications in the calculation results using the proposed models with respect to measurements. The results may have practical applications in assessing the effectiveness of acoustic enclosures, in which the basic construction material is an appropriate porous or fibrous plate, selected to have both sound-absorbing and sound-insulating properties.

Tube Dissipation estimation for the Transfer function method using Bayesian inference

Impedance tube measurement is commonly used in material research and building acoustics to study the acoustic properties of materials. However, air dissipation caused by multiple effects affects the accuracy of measurement results. This work discusses sound dissipation due to different effects in an impedance tube. The air layer method is used to measure the dissipation and to calibrate the tube. Accurate dissipation due to different effects is estimated by model-based Bayesian inference. The Bayesian analysis demonstrates the impact of tube dissipation on the acoustic measurements. The estimated tube dissipation drastically improves the accuracy of regular two-mic impedance tube measurements.

Monitoring cis-to-trans isomerization of azobenzene using Brillouin microscopy

Brillouin spectroscopy is commonly used to study the acoustic properties of materials. Here we explored its feasibility in studying the photoinduced isomerization of azobenzene. The isomerization of azobenzene changes the solution elastic modulus, and Brillouin scattering is sensitive to these changes. In this study, we experimentally demonstrated the photoswitching of azobenzene in DMSO using our home-made virtually imaged phased array-based high-resolution optical Brillouin spectrometer, and confirmed the results by ultraviolet–visible spectrophotometry. Remarkable Brillouin frequency shift variations were quantitatively recorded upon irradiation, and it was found that this method can indeed be used to monitor the isomerization process in situ. Importantly, our strategy also allows us to provide the relationship between the fraction of trans- and cis- azobenzene and the Brillouin frequency shift. This shows that Brillouin spectroscopy has broad prospects for the characterization of azobenzene isomerization and other photoresponsive materials.

Research on mechanics and acoustic properties of Jute fiber composite material

In this study, the loss of quality from the oxidative thermal decomposition of jute fiber was explored during the production of reinforced composite materials. Amino silicone oil was used to modify jute fiber, which was then subjected to thermogravimetric analysis. The modified fiber's thermal decomposition temperature was found to be 271 °C, enhancing the composite's thermal stability. The study also investigated how different jute fiber content affected the mechanical and sound absorption properties of composite materials. Results showed that jute fiber composites had better mechanical properties than pure polypropylene materials, and the average sound absorption coefficient of jute polypropylene composites increased with fiber content. Adding jute fiber to polypropylene effectively improved the sound absorption and noise reduction performance of the material. The average sound absorption coefficient of the composite material at a mass content of 20 wt% was 120 % higher than that of the polypropylene matrix material.

Designing hybrid aerogel-3D printed absorbers for simultaneous low frequency and broadband noise control

Recent studies have demonstrated that granular aerogels with sub-50 μm particles surpass conventional acoustic materials like glass fibers and polyurethane foams in low-frequency sound absorption. However, incorporating such granular materials within practical structural solutions remains a challenge. In this study, we use additive manufacturing to overcome this challenge by designing a modular geometry that allows us to encapsulate such granular materials within a 3D printed scaffold. Using the 3D printed porous scaffold provides the added benefits of tunability and durability. Further, we introduce a design methodology and software tool to facilitate the efficient design of such hybrid sound absorbers. The proposed method uses the Johnson-Champoux-Allard model, Biot theory, and the transfer matrix method to model the acoustical behavior of hybrid absorber designs that use layered granular aerogels and 3D printed bulk absorbers. The tool can also be used to inversely characterize the acoustic bulk properties of such materials. We validate the design concept and tool by comparing the model predictions with experimental measurements. Finally, we outline strategies for designing hybrid absorbers that can provide application specific low-frequency and broadband absorption performance within specific frequency ranges, while considering engineering constraints on their total mass and depth.

Review of the Low-Temperature Acoustic Properties of Water, Aqueous Solutions, Lipids, and Soft Biological Tissues.

Existing data on the acoustic properties of low-temperature biological materials is limited and widely dispersed across fields. This makes it difficult to employ this information in the development of ultrasound applications in the medical field, such as cryosurgery and rewarming of cryopreserved tissues. In this review, the low-temperature acoustic properties of biological materials, and the measurement methods used to acquire them were collected from a range of scientific fields. The measurements were reviewed from the acoustic setup to thermal methodologies for samples preparation, temperature monitoring, and system insulation. The collected data contain the longitudinal and shear velocity, and attenuation coefficient of biological soft tissues and biologically relevant substances-water, aqueous solutions, and lipids-in the temperature range down to -50 °C and in the frequency range from 108 kHz to 25 MHz. The multiple reflection method (MRM) was found to be the preferred method for low-temperature samples, with a buffer rod inserted between the transducer and sample to avoid direct contact. Longitudinal velocity changes are observed through the phase transition zone, which is sharp in pure water, and occurs more slowly and at lower temperatures with added solutes. Lipids show longer transition zones with smaller sound velocity changes; with the longitudinal velocity changes observed during phase transition in tissues lying between these two extremes. More general conclusions on the shear velocity and attenuation coefficient at low-temperatures are restricted by the limited data. This review enhance knowledge guiding for further development of ultrasound applications in low-temperature biomedical fields, and may help to increase the precision and standardization of low-temperature acoustic property measurements.

Acoustical Efficiency and Physico-Mechanical Characteristics Study for New Composite Material: Ethylene Vinyl Acetate and Wood Sawdust

Developing neoteric composite materials (CM) that improve the acoustic efficiency and mechanical properties become the target of many scientists in the last decade. This paper presents research on developing new CMs using Ethylene Vinyl Acetate (EVA) and sawdust (SD) of different weight concentrations which can be help to improve the acoustic and mechanical properties of the EVA polymer materials. Prototypes of EVA composite in form of flat plates with different weight concentrations of sawdust namely; 0, 2.5, 5, 10, 20 and 30% were produced. One of the interesting applications of this new CMs is to use it as a floor covering in buildings and manufactures. The acoustic efficiency parameters namely, impact noise reduction and sound absorption are experimentally studied. The obtained results articulate that covering floors with the designed composite material of EVA/SD as filler can decrease ISR up to 14 dB. Also, it gives peak sound absorption coefficient about 0.6 for 30 % of SD at mid-frequency band. The greatest proportion of SD aggregate EVA does not entail a higher acoustic performance. The tensile strength of the composite increases to 15.5% when the SD content is 5% and the tensile strength drops with increase the SD content up to 30%. Therefore, SD may be utilized as filler and consolidation in the EVA matrix, which will save expenses and assist the environment.

Effect of fibre treatment and moisture content on the vibration and acoustic properties of the basalt/hemp hybrid composites

The hybridization reinforcements of composites allow design engineers to enhance the structural and acoustic properties of synthetic fibre-reinforced materials. Natural fibres are considered to have higher potential for replacing synthetic fibres in the composite industry. The present study aims to develop hybrid composite materials for sound insulation applications in the automotive industry. The hybrid composites were developed by reinforcing Basalt and Hemp fibres with Epoxy using vacuum bagging technique and cured under ambient conditions. Vibration and acoustic experiments were carried out on pristine and aged BHU (Basalt-Hemp-Untreated) and BHT (Basalt-Hemp-Treated) specimens. The fibre treatment and moisture gain influenced the natural frequency and stiffness of the hybrid composites. With the fibre treatment, the natural frequency of the specimens was enhanced by 12.8%. With ageing of both BHU and BHT, specimens showed a reduction in the natural frequency by 16.4% and 23% respectively. Moisture ingression into the composites reduced the stiffness and improved the damping factor of the structure. The aged BHU and BHT showed better acoustic performance compared to the pristine specimens.

Increasing the accuracy of ISO 354 and ASTM C423 through modal identification

Measuring the acoustic properties of materials is a highly challenging task. Previous studies have highlighted errors in the absorption coefficient above 200 Hz, leading to absorption coefficient values higher than one. These errors are often attributed to differences in modal decays with and without the specimen. This effect is amplified in the case of highly reactive materials, such as innovative materials, that significantly impact the acoustic field and, consequently, the modal behaviour of the room. This work aims to reduce the difference between measured reverberation time values, with and without the specimen, through Data Augmentation. Modal identification was performed on measured impulse responses of porous specimens, where the alpha is known, allowing the determination of modal decay times and reverberation times within the frequency range of 70–180 Hz. A statistical analysis of natural modes and numeric solutions enables the identification of outliers. In this way, even in a non-well-optimized reverberation room, it is possible to enhance the accuracy of acoustic absorption measurements.

Acoustic and thermal properties of mycelium-based insulation materials produced from desilicated wheat straw - Part B

The acoustic and thermal properties were determined for biodegradable insulation materials produced from desilicated wheat straws with two different fungi and three different incubation periods. Ganoderma lucidum (GL) and Pleurotus ostreatus (PO) fungi and wheat straw were exposed to fungal incubation for 10, 20, and 30 days to produce mycelium-based insulation materials. The sound absorption coefficients of mycelium-based insulation boards produced using PO fungus were higher than those produced with GL fungus. It was found that the acoustic absorption coefficients of insulation boards produced using PO fungus at 1,000 Hz were 87 to 99% according to the incubation periods. The sound transmission losses of mycelium-based insulation boards produced ranged from 46.4 to 59.7 dBa at 1000 Hz. The group of boards labeled as YP2 exhibited the lowest level of sound transmission loss, whereas GL2 revealed the highest degree of sound transmission loss at 1000 Hz. The lowest thermal conductivity coefficient was obtained in insulation boards produced with PO fungus and an incubation period of 20 days. The limiting oxygen index (LOI) value of mycelium-based insulation materials was considerably higher than the insulation boards commonly used today. Thermogravimetric analysis and derivative thermogravimetry curves of mycelium-based insulation materials were also determined.

Акустические свойства мартенситно-стареющей стали XM-12 после энергетических воздействий

The study of the acoustic properties of maraging steels operated under various energy force and temperature actions is a critical task, since it is the method of acoustic structuroscopy that provides the most reliable connection with the structure, stress-strain state and mechanical properties of steels. The paper is devoted to research of the acoustic properties of the 15-5 PH maraging steel samples under various types of heat treatment under the conditions of mechanical tensile and cyclic loads. Samples of the 15-5 PH maraging steel were studied in three structural states: solid solution annealing and subsequent aging at 470 and 565 °C; during tensile tests; during cyclic tension-compression loading. The research used a unique scientific installation “Information-measuring complex for investigation of acoustic properties of materials and products”. It implements the acoustic mirror-shadow multiple reflections method using electromagnetic-acoustic and piezoelectric transducers based on polyvinylidene fluoride film to excite and receive waves and allows determining the velocity of wave propagation with an error of no more than 2 m/s. The acoustic (wave velocity, elastic moduli, electromagnetic-acoustical (EMA) transformation coefficients, acoustic anisotropy coefficients, acoustoelastic coupling coefficients) and electromagnetic (coercive force and electrical conductivity) characteristics of the samples were examined. The samples were studied in the initial state (before loading); stepwise in the process of tensile loads and subsequent unloading; after tensile tests; during cyclic tension-compression loading. It was revealed that the following acoustic parameters of 15-5 PH steel samples are the greatest structural sensitivity to mechanical tensile load and cyclic loading: transverse wave velocity, Poisson’s ratio, double EMA-transformation coefficient, and acoustic anisotropy coefficient.

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.