Acoustic Properties Of Materials Research Articles

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.

Integrated Analysis of Mechanical and Acoustic Properties of Materials

Integrated Analysis of Mechanical and Acoustic Properties of Materials

Lagrangian Formalism for the Analysis of Acoustic Properties of Two-Phase Composite Materials with Damaged Interfaces

Lagrangian Formalism for the Analysis of Acoustic Properties of Two-Phase Composite Materials with Damaged Interfaces

Effects of urea–formaldehyde and polyvinyl acetate adhesive on sound absorption coefficient and sound transmission loss of palmyra palm fruit fiber composites

Composite materials made from palmyra palm fruit fiber (PPFF) were formed using urea–formaldehyde (UF) and polyvinyl acetate (PVAc). We prepared two sets of five different cylindrical samples with varying PPFF contents. The PPFF composites’ normal-incident sound absorption coefficient (SAC) and transmission loss (TL) were measured by using the impedance tube method. The sample with higher PPFF content shows a lower SAC spectrum. It is the opposite for the TL, where a sample with high PPFF content demonstrates a higher TL spectrum. We conducted the least-square fitting method on the experimental SAC and TL spectra utilizing the Johnson-Champoux-Allard (JCA) equivalent fluid model. Non-acoustic parameters were acquired from the fitting. The optimized porosity (ϕ), viscous characteristic length (Λ), and thermal characteristic length (Λ′) are inversely proportional to the PPFF content. The airflow resistivity (σ) and tortuosity (α∞), on the other hand, demonstrate a direct correlation with the PPFF content. Even though the UF samples have an average density of 14.7 % higher than the PVAc samples, their σ,Λ′, and α∞ are just 7.7 %, 4.5 %, and 0.39 % higher than PVAc samples. On the other hand, PVAc samples show higher average Λ and ϕ of 1.4 % and 0.73 %, respectively. The optimized porosity values obtained from the JCA model (ϕJCA) are coherent with ones from the direct estimation method assuming adhesive-coated fiber (ϕfa). It can be concluded that the adhesive’s quantity and density contribute to the composites’ porosity value, ultimately affecting material acoustic properties. Researchers can control and predict how the SAC and TL of fibrous sound absorbers would behave by varying the quantity and density of an adhesive.

A Multilayered, Lesion-Embedded Ultrasound Breast Phantom with Realistic Visual and Haptic Feedback for Needle Biopsy.

Anthropomorphic phantoms have been used to provide residents with training in ultrasound-guided breast biopsy. However, different individuals differ in terms of the acoustic properties and stiffness of their breast tissues. The individual differences should be reflected in the training breast phantoms. This study aimed to develop a breast tissue-mimicking phantom that offers realistic haptic feedback and ultrasound imaging during needle insertion. We investigated the tunability of the mechanical and acoustic properties of breast tissue-mimicking materials (TMMs) to emulate fat, glandular and tumor tissues. The Design of experiments (DOE) methods and physician's feedback were used to reveal the effect of component concentration on Young's modulus and acoustic properties of breast TMMs. Furthermore, the relative backscatter power of the TMM was studied to adjust the contrast between the simulated tumor and background glandular tissue. The results indicated that Young's moduli of TMMs could be altered by adjusting the concentrations of glycerol, agar and olive oil. Changing the concentration of silicon carbide in a TMM could enhance the contrast between the target and the background materials in an ultrasound image. Finally, a series of TMMs were suggested for fat, glandular, benign tumor and malignant tumor tissues. A breast phantom with a tunability appropriately reflecting the individual differences of breast tissues was developed.

Fabrication and Characterization of Tissue-Mimicking Phantoms for Ultrasound-Guided Cannulation Training.

Tissue-mimicking materials (TMMs) have been investigated and used for decades as imaging phantoms in various medical applications. They are designed and fabricated to replicate certain biological tissue characteristics, a process often dictated by the target application. Moreover, TMMs have been utilized in some medical procedural training requiring the use of imaging modalities. One potential application for TMMs is ultrasound-guided cannulation training. Cannulation is a procedure that requires a level of dexterity to gain vascular access using ultrasound guidance while avoiding complications like vessel laceration and bleeding. However, an ideal phantom for this application is yet to be developed. This work investigates the development and characterization of high-fidelity phantoms for cannulation training. The mechanical (shore hardness, elastic modulus, and needle-interaction forces) and acoustic (B-mode ultrasound scans) properties of candidate materials were quantitatively compared with biological tissue. The evaluated materials included ballistic gel, plasticized polyvinyl chloride (PVC), silicone, gelatin, agar, and polyvinyl alcohol (PVA)- cryogel. Mechanical testing demonstrated that each material could replicate the Shore hardness and elasticity characteristics of different biological tissues (skin, fat, and muscle), with PVA and PVC showing tunability by varying composition or fabrication processes. Shore hardness (OO-range) for PVA ranged between 6.3 ± 1.0 to 59.3 ± 2.6 and PVC from 4.8 ± 0.7 to 14.6 ± 0.8. Ultrasound scans of PVA were the closest to human scans, both qualitatively (based on experts' opinion) and quantitatively (based on pixel intensity measurements). Modified mixtures of PVA are found to best serve as high-fidelity cannulation phantoms. Alternatively, PVC can be used to avoid troublesome fabrication processes of PVA.

A finite difference approach for predicting acoustic behavior of the poro-elastic particle stacks

The physical properties of particle stacks have been of interest for a long time, and the acoustic properties of such materials have been actively investigated in recent times. Traditional acoustic theories, such as the Biot theory, can serve as a guide for determining the general properties of the stacks, but they do not allow the identification of the differences between the particle stacks and traditional acoustic materials, which are usually modeled as homogeneous continua. Recent research suggests that the Biot theory, combined with depth-dependent stiffness and equivalent density, can be used to model such materials. In this work, a finite difference (FD) scheme based on the Biot theory has been developed based on the idea that the apparent stiffness of the particle stack varies with depth within of the stack. This FD scheme is two-dimensional in cylindrical coordinates with an axisymmetric condition imposed at the axis of the cylinder. This approach is thus suitable for modeling common scenarios in which particle stacks are tested in a cylindrical standing wave tube. The results of several example cases are shown in this paper.

Computational investigation into the effect of material properties on aeroacoustics based damage detection from wind turbine blades

A wind turbine blade monitoring system would provide significant benefit to wind farm owners and operators by reducing operation and maintenance costs and increasing energy production by limiting turbine downtime. Previous work has demonstrated potential success of a system based on monitoring the flow-generated sound with blade internal cavity microphones. In this study, the effect of blade material acoustic properties is investigated to provide recommendations on the potential application of this approach. A reduced-order model is used to identify the flow-generated lumped-parameter acoustic sources outside the blade at a frequency of 10 kHz. A feasible range of acoustic properties is used for the blade and shear web acoustic transmission coefficient and acoustic reflection coefficient. Damage detection success improved as reflection increased, as more sound propagated toward to the root of the blade. However, the damage detection success rate did not consistently increase with an increase or decrease in the transmission coefficient and balance must be achieved depending on the specific blade and the expected flow-generated sound. These results demonstrate the usefulness of quantifying the blade material acoustic properties and will be used to strategically design a blade monitoring system.

Acoustic properties of commercially available thermal insulators − An experimental study

Thermal insulators are used structural applications, such as walls, floors, doors, roofs, duct wrappings, machine and wall linings, and vehicle envelopes. There is very little scientific comparative research about the acoustic performance of thermal insulator materials. The purpose of our study was to compare various acoustic properties of insulator materials to improve comprehensive understanding. Thirteen commercially available insulator types produced by several manufacturers were studied for thicknesses 50, 100, and 200 mm. The materials were stone wool, glass wool, cellulose, wood fiber, expanded polystyrene, polyisocyanurate, phenol foam, and cellular glass. Six acoustic quantities were measured: sound reduction index of bare insulator, sound reduction index of encapsulated insulator (insulator between two boards), sound absorption coefficient, airflow resistivity, dynamic stiffness, and reduction of impact sound pressure level in a floating floor. The acoustic performance differed significantly between insulator types for each quantity. The value range for the abovementioned six quantities for 100-mm thick insulator was extremely large: 10–27 dB, 33–52 dB, 0.20–0.78, 3.0–2700 kPa s/m2, 1.5–730 MN/m3, and 15–36 dB, respectively. Closed-pore materials usually carried worse acoustic properties than open-pore materials. Unexpectedly, lower thermal conductivity was associated with worse acoustic performance of two acoustic quantities. The study is the broadest acoustic investigation of thermal insulators because of the large number of studied acoustic quantities and insulator types. The study provides strong evidence that the choice of thermal insulator material plays an important role in the acoustic properties of the structural application. Manufacturers should consider declaring all six acoustic quantities to facilitate design.

Synthesis and research of basalt microfiber‐reinforced polyurethane elastomer composites

AbstractBasalt microfiber‐reinforced polyurethane elastomer composites (BMF/PUE) were prepared by semi‐prepolymer method in this study. The degree of microphase separation and quantitative analysis of H‐bonding formation in polyurethane were determined by infrared spectroscopy. The fiber surface and the morphology at the tensile fracture interface of the composite materials were observed by scanning electron microscopy. The mechanical properties of composite materials were further measured on an electronic universal testing machine. Dynamic thermomechanical analysis and acoustic impedance tube were used to study the damping and acoustic properties of composite materials, respectively. The results indicated that the composite material prepared by adding 6 g of basalt microfibers treated with 3 min' crushing had the best overall performance. Compared with the matrix, BMF/PUE showed good sound insulation performance with a much wider effective damping temperature range. On the basis of ensuring its excellent overall performance, the mechanical properties were increased by 50.4% in tensile strength, 28.1% in elongation at break, and 14.2% in tear strength.

Experimental Validation of the Model of Reverberation Time Prediction in a Room

It is well known that the uncertainty of input data has a great influence on the accuracy of room acoustics simulations. The aforementioned accuracy is significantly influenced by the selection of the acoustic properties of room-delimiting materials. Moreover, simulation errors are attributed to the fact that rooms can be very irregular and sound diffusion can be uneven, and thus sound absorption can be unevenly distributed over the surfaces. Therefore, a very important element is the validation of the simulation model of interior acoustics, even when we use ready-made software dedicated to interior acoustics for the simulation. In the article, the reverberation room model simulated in the ODEON program was subjected to validation. The program is based on a hybrid method combining the ray and virtual source methods. For the validation, appropriate measurements of the reverberation time in that room were carried out. The validation was undertaken using the criterion of correct validation, consisting of comparing the value of the comparison error and the value of the validation uncertainty.

Influence of Fe2O3 Content on Acoustic Properties of Backing Materials and Development and Utilization of Acoustic Emission Sensors

Fe2O3 and epoxy resin sensor substrate materials (Fe2O3/epoxy resin composite material) are prepared in this article. A series of acoustic emission sensors are prepared by using composite material as sensor substrate, and the effect of Fe2O3 content in composite material on sensor performance is studied. The effect of Fe2O3 content in the composite material on the performance of the sensor is studied through the simulated lead‐breaking experiment, and the self‐made sensor is calibrated by using the calibration system. Nondestructive testing of concrete materials with different strengths is carried out by selecting the sensor with the best performance. The results show that the content of Fe2O3 in the composite increases to 50%, the epoxy resin matrix reaches saturation point of accommodate Fe2O3 powder, and the propagation velocity of ultrasonic waves reaches the lowest point when it passes through the composite. The sensor with 50% Fe2O3 content as a backing layer has the highest sensitivity and signal‐to‐noise ratio. The relationship between the strength of concrete material and acoustic attenuation and frequency is established by using this sensor, and the law can be used to evaluate the strength and mechanical properties of concrete material without destroying them.

In situ acoustic characterization of a locally reacting porous material by means of PU measurement and model fitting

Reliable data on acoustical properties of materials are crucial for the design of a desired acoustic environment as well as to obtain accurate results from acoustic simulations. Although the acoustical properties of materials can be obtained via laboratory measurements, situations where in situ measurements are needed are often encountered. However, in situ measurement methods presented so far are limited by their poor portability or inaccuracies in the low-frequency range. In this work, we propose a characterization method that combines an in situ pressure-velocity (PU) measurement with a model fitting procedure using the Delany-Bazley-Miki impedance model for porous materials. The method uses an optimization routine to find the best match of measured and modelled reflection coefficient values within a given frequency range for the optimization parameters: flow resistivity, panel thickness, and probe-sample distance. The optimal parameter values allow, in turn, calculating the porous panel’s reflection coefficients for a broad frequency range including frequencies below the lower bounds of the optimization frequency range. The sensitivity of the method to panel width, lower bound of fitting frequency range, and to excluding parasitic reflections by time windowing is studied. The study shows that the proposed method provides characterization results in good agreement with reference data for panels of dimensions larger than 1800 mm and that the method is robust for reduction of one dimension of the panel down to 300 mm. It also shows that the model fitting accuracy is best when the frequency range of analysis is restricted to 1000–5000 Hz.

The Effect of Composition, Pre-Treatment on the Mechanical and Acoustic Properties of Apple Gels and Freeze-Dried Materials.

This study aimed to determine the effect of the addition of apple juice concentrate (AJC) on the properties of agar gel and dried materials. Agar gels with the addition of apple juice concentrate in the range of 5–20% were prepared with or without the addition of maltodextrin. The gels were also soaked in the solution of AJC. The water content, water activity, densities, some mechanical and acoustic descriptors of gels, and the freeze-dried gels were analysed. The porosity and shrinkage of dried products were also investigated. The addition of AJC significantly changed mechanical and acoustic properties of gels. The hardness of gels decreased with a higher addition of concentrate. Dried samples with a lower concentration of sugars (the lower addition of AJC) were characterised by lower shrinkage and higher porosity, as well as crispness and glass transition temperature. The investigated mechanical and acoustic properties of dried gels showed the addition of apple concentrate at the level of 5% to agar solution was optimal.

Research on Acoustic Absorption Properties of Aramid Honeycomb Composite Material Reinforced by Polyimide Foam

To endue sound absorption behavior for aramid honeycomb core (ARHC), isocyanate‐based polyimide foam (IBPIF) with excellent thermal insulation and acoustic properties produced by a new formulation of foaming slurry is filled into ARHC by the free foaming route. As a core factor to adjust the cellular structure of IBPIF, the effect of water dosage on the acoustic behavior of IBPIF and IBPIF filled ARHC (IBPIF/ARHC) is studied, and the optimal formula to produce IBPIF/ARHC is filtered out. Results suggest that water dosage effectively regulates the cellular structure of IBPIF. When water dosage is 7.2 g, IBPIF has a large windows opening rate, which plays a positive role in sound absorption performance. IBPIF/ARHC‐3 has the best sound absorption property, which possesses a maximum sound absorption coefficient (α) of 0.9 at 1500 Hz. Its average α increases to 0.78 and shows an increase of 680% compared to ARHC. Meanwhile, the density of IBPIF/ARHC is only about 59 kg m−3. In 300–600 Hz range, IBPIF‐3 and ARHC show obvious synergy effects in sound absorption behavior. The average α of IBPIF‐3 and ARHC is only 0.3 and 0.06, respectively, and that of IBPIF/ARHC‐3 reaches up to 0.42. The thermal insulation performance of ARHC is also improved, and thermal conductivity decreases from 0.067 to 0.047–0.049 W (m K)−1.