•Polymeric sound absorbers can be produced through electrospinning, materials with a fiber diameter from few nanometers to several micrometers.•A numerical simulation model of the acoustic behavior ...of poly vinyl pyrrolidone/silica composites were developed.•The results of the measurements of the sound absorption coefficient were analyzed.•The results of the numerical modeling of the acoustic coefficient were reported.•The neural network-based model showed high Pearson correlation coefficient values (0.942), indicating many correct predictions.
Polymeric sound absorbers can be produced through electrospinning, a process which allows to fabricate high specific surface materials with a fiber diameter from few nanometers to several micrometers. In this study, a numerical simulation model of the acoustic behavior of poly vinyl pyrrolidone/silica composites were developed. First, the characteristics of the poly vinyl pyrrolidone/silica composites were examined, and the manufacturing of the material were described. Subsequently, the results of the measurements of the sound absorption coefficient were analyzed. Finally, the results of the numerical modeling of the acoustic coefficient were reported. The neural network-based model showed high Pearson correlation coefficient values (0.942), indicating many correct predictions. Taking into account the bell shaped acoustic response of the studied blankets as a function of frequency, the possibility to foresee the needed mass with the neural network-based model will be of great value for the applications where high acoustic absorption is required in specific limited frequency ranges.
•A numerical model is proposed to calculate the normal, oblique, and random sound absorption coefficients of microperforated panel absorbers (MPPAs).•Acoustical properties of the proposed wavy MPPA ...are investigated and the mechanisms behind its sound absorption performance are explored.•A compact wavy MPPA with broadband random sound absorption performance is obtained.•Experiments are performed to validate the proposed model and verify some of the numerical findings.
In this study, the sound absorption performance of a wavy micro-perforated panel absorber (WMPPA) is investigated. First, a numerical model is established to calculate the sound absorption coefficients of micro-perforated panel absorbers (MPPAs) under normal, oblique, and random incidences. Subsequently, the proposed model is validated using an existing theoretical formula. After that, the acoustical properties of a WMPPA are explored and then compared with those of flat and corrugated micro-perforated panel absorbers (FMPPAs, CMPPAs). It is observed that the normal sound absorption curve of the WMPPA shifts to a lower frequency range compared with those of CMPPA and FMPPA, which is promising for the control of low-frequency noise. Besides, the sound absorption performance of the WMPPA at the dips is considerably improved, which is favourable for the reduction of broadband noise. Modal analysis shows that, apart from the resonant mode, the adjacent non-resonating modes are also excited, which enhances the performance. Moreover, the WMPPA exhibits the properties of a multiple-layered MPPA, and extra sound absorption peaks are observed within the middle- to high-frequency range. In addition, a parametric study is conducted to explore the influence of the corrugation depth and offset distance on the sound absorption performance of the WMPPA. The calculated results demonstrate that the proposed WMPPA is suitable for low-frequency and broadband noise control. Furthermore, a compact WMPPA with a high random sound absorption coefficient is obtained following an optimization scheme. Finally, the sound absorption coefficients of the MPPAs under normal plane-wave incidence are obtained experimentally using an impedance tube. The measurement results agree well with the simulation results, validating the proposed model and verifying some of the numerical findings.
Novel sound insulation biocomposite materials have been elaborated using treated alfa fibers and sawdust wood fibers as reinforcing materials, and polyvinyl acetate as a binder agent. Alkaline ...treatment was applied to alfa fibers to remove the resin from the steams. X-ray diffraction, Scanning electron microscope and Fourier-transform infrared spectroscopy have been performed to ensure the undesirable substances have been removed. The sound absorbing properties have been investigated by the two-microphone impedance tubes of type 4206 B&K test. The recorded data were compared and analysed, especially in medium and high frequencies. The maximum value of the sound absorption coefficient corresponding to spruce and beech wood fibers based composites are 0.98 at 2048–2288 Hz and 0.98 at frequency range respectively.
The size of the air gaps thickness and of the additional woven flax shell layer has some significant effects especially for the low frequencies. The results obviously show that the use of the biocomposites based on alfa fibers and wood fibers, for sound absorption applications, represents a smart choice and could be used as an alternative way to conventional materials based on synthetic fibers used for sound absorbing panels.
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•SAP-net with CNN to predict the sound absorption coefficient of metaporous materials.•Enormous acceleration achieved (7ms/image) for the prediction process.•Trained SAP-nets show ...outstanding accuracy with MAE averagely smaller than 0.02.•SAP-net’s ability to learn the underlying mechanism of topology-performance linkage.•New fast and accurate tool for investigating sound absorption and designing materials.
Airborne sound absorption coefficient is the premise for investigating the sound absorption performance or mechanism of metaporous materials. The common numerical evaluation approach is FEM which is relatively computationally costly particularly when processing complex structures or a large batch of data. Rapidly developing deep learning algorithms, on the other hand, show a promising trend in the data-driven manner to learn and predict material parameters efficiently and precisely. We propose SAP-net based on deep convolutional neural network to predict the sound absorption coefficient at a specific frequency of an input image representing the topological structure of metaporous materials. Trained with FEM-prepared data for six frequency points, SAP-net demonstrates outstanding evaluation speed of 0.007 s/image and brilliant prediction accuracy with mean absolute errors all smaller than 0.019 (the smallest 0.008 at f = 1000 Hz). Meanwhile, the fact that SAP-net remains accurate when predicting for images that are essentially different from those in the training data shows its capability of learning and capturing the underlying physical mechanism linking the topological structure to the sound absorption performance. In conclusion, SAP-net provides an extraordinarily fast and accurate approach for the investigation of sound absorption performance, which is expected to accelerate the examination and design process of materials.
This paper presents the sound absorption performance of natural fiber composites developed from chrome shave (CS) and coffee silver skin (CSS). Twelve test samples of thickness 30 mm and 50 mm were ...fabricated with different fiber sizes and fiber ratios and by maintaining the density of the samples by 150 kg/m3. Normal incidence sound absorption coefficient spectra were measured in an impedance tube. Absorption coefficient spectra were predicted using the Johnson-Allard-Champoux (JCA) model using best fit values of tortuosity and the two characteristic lengths together with measured values of porosity and flow resistivity.
The results revealed that the CS-CSS composite had average absorption coefficient of 0.95 above 1 kHz for a thickness of 30 mm and 50 mm. 'The predictions and data are in good agreement up to 6 kHz.
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•Aerogels based on PVA, nanoclay and trGO were successfully synthesised.•trGO presence into aerogel improved the value of the sound absorption coefficients.•Average pore diameter of ...aerogel decreases with the graphene oxide incorporation.•trGO introduction into the aerogel enhanced the thermal stability of the final product.
Aerogels based on a ternary system of polyvinyl alcohol (PVA), nanoclay and thermally reduced graphene oxide (trGO) have been synthesised at pilot plant scale using an environmentally friendly freeze-drying method. In the present work, the influence of the trGO addition on the physical, thermal and acoustic properties of the resulted aerogels has been evaluated. The trGO incorporation into the PVA/nanoclay matrix resulted in pore diameter decrease. In addition, trGO addition allowed to improve thermal stability of the aerogels. On the other hand, the introduction of the trGO resulted in improvements of the sound absorption coefficient of the aerogels. This process opens new opportunities to produce materials with exceptional properties as thermal insulators (resulting values of the thermal conductivities ranging from 0.0255 to 0.0289 W/m·K) with enhanced sound absorption properties.
Among fibers with lignocellulosic origin, Kenaf fiber, because of its advantages and as a sustainable alternative to synthetic fibers has received increasing attention for manufacturing hybrid ...composites with reasonable acoustical and physical properties. The present study deals with the impact of chemical treatment of Kenaf fibers on the overall properties of hybrid composites fabricated from these fibers. Also, the results from predictive analytical model of sound absorption for these composites were employed for comparison with the experimental findings. Kenaf fibers were treated at room temperature with 6% concentration of sodium hydroxide (NaOH) and 4 h immersion time. Having manufactured the composites with the treated and untreated fibers, the normal sound absorption coefficients and tensile strength properties of these sample composites were determined according to ISO 10534-2 and ASTM C1557 − 14, respectively. The SEM analysis of the treated and untreated fibers revealed that in terms of fiber diameter and morphology the former was thinner and had better surface appearance. The experimental measurement of acoustic absorption coefficients of the composites made of treated fibers demonstrated superior sound absorption properties and tensile strength. The revised empirical models proposed by Delany & Bazley and Garai & Pompoli along with Nelder-Mead simplex method were employed and well predicted the sound absorption coefficients of the sample composites. There was also a fair consistency between the experimental and predicted results.
•Estimation of sound absorption coefficient of multi-layered acoustical materials.•Artificial neural network (ANN) was used.•ANN considered thickness, density, specific airflow resistivity, and ...sequence.•Proposed ANN model showed better estimation accuracy than the transfer matrix model.
The feasibility of a data-based artificial neural network (ANN) for the estimation of the sound absorption coefficient of a layered fibrous material is investigated in this study. The sound absorption coefficient of a four-layered fibrous material was estimated using a well-trained ANN model with only one non-acoustical parameter: the airflow resistivity (σ). The results indicated that the ANN model exhibits a good correlation between the estimated and measured absorption coefficient. The training data sets were built by carrying out experimental measurements using a two-microphone impedance tube with 230 combinations of four-layered fibrous materials. The results of the ANN are compared in three different cases with the transfer matrix method (TMM), which is the conventional method of estimating the sound absorption coefficient of multi-layers using several non-acoustical parameters. The sound propagation model in acoustical material for the TMM was used by two models proposed by Delany-Bazely (one non-acoustical parameter) and Johnson-Champoux-Allard (five non-acoustical parameters). By comparing the estimated sound absorption coefficient from the ANN and TMM with measured values, it was demonstrated that the model developed in this paper gives more accurate results within the defined conditions. The results were compared in the frequency range of 3000–6000 Hz, and the error of the ANN model was less than 1.67%.
•The pineapple leaf fibres can have average absorption coefficient of 0.9 above 2 kHz.•Introducing the air gap has can effectively improve the frequency bandwidth of absorption especially for thin ...samples.•The PALF also have comparable sound absorption coefficients with those of mineral rock wools and synthetic polyurethane foam.
This paper reports the utilisation of fibres from the pineapple leaf (PALF) to be an alternative natural acoustic material. We fabricated samples from raw pineapple leaf fibres with different densities and thicknesses to observe their effects on the sound absorption characteristic. Measurement was conducted for the normal incidence sound absorption coefficient in an impedance tube based on ISO 10534-2. It reveals that the pineapple leaf fibres can achieve sound absorption coefficient of 0.9 on average above 1 kHz by controlling the densities of the fibres and/or by introducing the air gap behind the samples. It is also demonstrated that the sound absorption performance is similar to that of the commercial rock wool fibres and synthetic polyurethane foam.
In recent years, the use of natural materials in acoustic applications has drawn a lot of interest as a viable and eco-friendly substitute for synthetic materials. This study examines the potential ...for sound absorption by natural materials and assesses how well they perform acoustically. The following factors are taken into account when assessing a material's acoustic performance: fibre size, thickness, density, porosity, pore tortuosity, and flow resistance. In-depth discussion is also given on the physics of sound wave interaction and the methods used to calculate the sound absorption coefficient. Kenaf, coconut fibre, jute felt, rice straw, tea leaf fibre, sugarcane bagasse, date palm fibre, and wool are among the sustainable resources that are the subject of the study. For kenaf, in particular, the effect of bulk density and thickness on sound absorption is examined. The study's findings demonstrate the potential of natural materials to offer reliable sound absorption options while fostering sustainability. Because they are renewable, biodegradable, and have a smaller environmental impact than synthetic materials, natural materials can be used in acoustic applications. Natural materials also have special acoustic characteristics that can be enhanced with the right preparation and handling. This study shows the potential of natural materials in offering sustainable acoustic solutions and offers useful insights for architects, engineers, and researchers working in the field of acoustic design. The results of this study can aid in the creation of new and enhanced acoustic materials, hence fostering sustainability and minimising the negative environmental effects of the built environment.
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