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Noise control is an environmental problem of first magnitude nowadays. In this work, we present a new concept of acoustic screen designed to control the specific noise generated by transport infrastructures, based on new materials called sonic crystals. These materials are formed by arrangements of acoustic scatterers in air, and provide a new and...
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... FHWA U.S. A., 2001). The acoustic effect of ABs can be explained as follows: They reflect or scatter back towards the source a portion of the transmitted acoustical energy and other portion of the noise energy is absorbed by the material of the barrier. Other portion is transmitted through the barrier or diffracted from the barrier's edge (Fig. 1a). This diffraction can be considered as one of the main factors that decreases the effectiveness of the barriers (Harris, 1991;Kotzen and English, 1999). In fact, this is one of the main research lines in the field of classical ABs, focused on reducing this diffraction effect over the top edge, by designing new profiles far away from ...
Citations
... Among the advantages associated with the use of this technology, it is also important to note the low weight and ventilation capability of the structures. In fact, the openness of these barriers allows a limitation on the loads acting on the foundation and a reduction in their costs [12], decreasing the overturning moment due to wind or shock wave from high-speed vehicles. This type of "more open" noise barrier also allows some continuity of the visibility and passage of air through the discrete elements forming a lower visual impact barrier [13] and contributing to higher social acceptance. ...
Recent research has been developed by different groups towards the development of sonic crystals as noise barriers. The present paper aims to contribute to this research, focusing on the possible application of this technology in practice, and exploring some aspects that may be useful for its further development. One of the objectives of this work is to explore the differences between experimental results obtained under laboratory conditions and numerical results computed with the finite element method (FEM), in 2D and 3D, understanding if different types of simplified models can be of use in the practical analysis of sonic crystals. Through this comparison, a validation of the prediction numerical models is performed, giving confidence for their use in the development and study of sonic crystal configurations. In this context, different geometric arrangements of the sonic crystals’ scatterers (the individual elements that make up the barriers) have been analyzed with the help of the numerical method, evaluating their behavior in different arrangements of numbers of elements, shape and size. A number of parametric studies are also performed introducing some randomness in the structure (in scatterer size and spacing), and analyzing its effect on the insertion loss provided by the sonic crystal. These contributions can be significantly useful for the development of new solutions, giving important hints about the sensitivity of these structures to possible defects or limitations in their production.
... With a proper design, sonic crystal can attenuate sound on a broader frequency range than previous acoustic metamaterials 15,16,17 . Previous works have shown that the combination of sonic crystal and acoustic absorber has higher sound absorption than each system on its own 18,19 . The addition of sonic crystal is expected to enhance sound absorption of vegetation, especially in the low-mid frequencies where bandgaps are present. ...
... The performance of a particularly active technique has been affirmed by utilizing a committed noise dropping lab casing. This methodology is applied to actual device casing, a significant step towards commercializing the dynamic casing technique [106][107][108]. ...
This article analyses the most recent studies on urban traffic noise. About 67 relevant articles on urban road traffic noise and its mitigation strategies were preferred for a critical review. Only 5.97% of items describe how to monitor and record the noise measurement for urban roads, while 7.46% of articles enumerated urban traffic noise pollution exposure. 29.85% of articles proposed a model to evaluate noise reduction effects and predict the noise level. Also, many articles reported noise map generation and its analysis. 56.71% of articles described the noise mitigation strategies in detail, concerning noise control by green vegetation, land use planning, low noise tire and pavement material, noise reduction through façade shielding. Noise pollution standards are being breached in all areas. There is a need for the proper implementation of rules and regulations. Therefore, noise mitigation strategies such as designing noise barriers and other noise control materials are needed. Finally, it is summarized that economic and low-cost optimized noise pollution mitigation strategies like ingeniously made noise barriers, vegetation and landscaping are need of the hour for urban areas of developing countries.
... Thin plate structure is a common structure in engineering. With advantages of light weight, energy saving, low cost, and environmental protection, thin plate structure has been widely used in various equipment [6]. However, thin plate structure is also an excellent radiation body that generates vibration and radiated noise in response to forced vibration [7]. ...
The influence of acoustic radiation is considered in the prediction of noise attenuation effect of sound barrier, which provides a theoretical reference for further improving the insertion loss of sound barrier. Based on the theory of thin plate vibration, the vibration mode and natural frequencies of sound barrier under arbitrary boundary conditions are established by using two-dimensional beam function method, and the forced vibration response of the sound barrier is calculated based on the modal superposition method. MATLAB software (MathWorks Company, Natick, Massachusetts, USA) is used to calculate the natural frequencies and the radiated sound power level of the sound barrier, which indicated that the sound radiation caused by external excitation would significantly increase the sound pressure level at the received point, which should be considered as one of the influencing factors in the prediction of noise attenuation effect. The influence of diverse structural parameters on the radiated acoustic power is compared, providing an excellent reference for the design of sound barrier with low noise.
... The SB behaviour and associated sound attenuation was also investigated for 2D periodic square lattices of rigid square rods [112] and 2D periodic triangular lattices of rigid cylinders in air [38,278]. The potential of such acoustic PCs as sonic barriers for the human audible frequency range was further investigated in among others [111,112,178,248,267,277,279]. An example of a PC based sonic barrier realisation is the periodic triangular lattice of bamboo rods, introduced by Lagarrigue et al. [180] ( Fig. 1.1). ...
Over the past decades, tightening ecologic and economic requirements have urged industry to introduce lightweight design. Lightweight structures typically combine low mass with high stiffness, which impairs their noise and vibration insulation performance. This conflicts with rising customer expectations and increasingly stringent noise exposure regulations. Classical solutions to improve the vibro-acoustic performance usually rely on adding mass or volume, conflicting with lightweight design requirements. In the search for novel solutions that can comply with these conflicting requirements, vibro-acoustic locally resonant metamaterials have recently emerged and shown promising potential. By introducing resonators on a sub-wavelength scale to a flexible host structure, a stop band can be created, which is a frequency range in which no free wave propagation is possible. By creating resonance-based stop band behaviour for the bending waves in flexible partitions, a targeted frequency range of strong noise and vibration attenuation can be achieved. The sub-wavelength nature of locally resonant metamaterials can enable lighter and thinner vibro-acoustic solutions, also able to target the hard-to-address low frequency range.
While the potential of vibro-acoustic locally resonant metamaterials has been demonstrated, the transition towards engineering solutions still requires more accurate and robust vibro-acoustic performance predictions. Damping is inherently present in locally resonant metamaterial realisations and affects their vibro-acoustic attenuation performance. Whereas damping tends to reduce the peak attenuation, it has also shown potential to broaden the frequency range of attenuation. However, damping is usually omitted in the modelling of locally resonant metamaterials, hampering accurate vibro-acoustic performance predictions. Moreover, while their predominantly narrowband performance makes locally resonant metamaterials especially suitable for vibro-acoustic problems in targeted frequency ranges, achieving broadband vibro-acoustic performance is highly desired. In view of attaining broadband performance, the potential role of damping needs to be further clarified.
The main goal of this dissertation is to assess the impact of damping on the vibro-acoustic performance of locally resonant metamaterial plates, in order to gain physical insight in the effects of damping, to obtain more accurate vibro-acoustic performance predictions and to investigate the broadening of the frequency range of attenuation.
After investigating the translation from bending wave stop band behaviour to acoustic insulation improvements, the impact of damping on the vibration attenuation of locally resonant metamaterial plates has been assessed by means of dispersion curve analysis. The vibration attenuation in and around the stop band is mainly governed by the resonator damping, reducing the peak attenuation inside the stop band and increasing the attenuation in a broadening frequency range around the stop band. Damping in the host structure mainly increases the vibration attenuation outside the stop band. The damping influenced vibration attenuation predictions have been experimentally validated by means of dispersion curve measurements.
The impact of damping on the sound transmission loss has next been analysed for infinite periodic and finite locally resonant metamaterial plates. The sound transmission loss in and around the stop band is mainly governed by the resonator damping, reducing the peak attenuation and improving the possible low-frequency coincidence zone after the stop band. The resonant sound transmission due to structural modes outside the stop band is reduced in a broadening frequency range around the stop band. Damping in the host structure mainly reduces the resonant sound transmission outside the stop band. The damping influenced sound transmission loss predictions have been experimentally validated by means of insertion loss and sound transmission loss measurements.
Eventually, in view of improving and broadening the acoustic insulation performance, the potential of a locally resonant metamaterial double panel has been analysed and experimentally investigated.
... The results in Figure 2 show how the triangular shape with alternately turned faces has the highest absorption peak, but that the band gap results at frequencies above 2 kHz can be suitable for the mitigation of industrial sources with a narrow noise emission spectrum. In the road traffic noise frequency band [46], the scatterers' shape bringing the greatest IL is the elliptical one with the long side facing the source. However, the most used type is the circular one, which shows an IL of less than 5 dB in frequencies around 1 Hz with respect to the elliptical one. ...
Noise barriers are the most widespread solution to mitigate noise produced by the continuous growth of vehicular traffic, thus reducing the large number of people exposed to it and avoiding unpleasant effects on health. However, conventional noise barriers present the well-known issues related to the diffraction at the edges which reduces the net insertion loss, to the reflection of sound energy in the opposite direction, and to the complaints of citizens due to the reduction of field of view, natural light, and air flow. In order to avoid these shortcomings and maximize noise abatement, recent research has moved toward the development of sonic crystals as noise barriers. A previous review found in the literature was focused on the theoretical aspects of the propagation of sound through crystals. The present work on the other hand reviews the latest studies concerning the practical application of sonic crystal as noise barriers, especially for road traffic noise mitigation. The paper explores and compares the latest developments reported in the scientific literature, focused on integrating Bragg’s law properties with other mitigation effects such as hollow scatterers, wooden or recycled materials, or porous coating. These solutions could increase the insertion loss and frequency band gap, while inserting the noise mitigation action in a green and circular economy. The pros and cons of sonic crystal barriers will also be discussed, with the aim of finding the best solution that is actually viable, as well as stimulating future research on the aspects requiring improvement.
... Noise reduction has direct influence upon the healthy environment for living and working. The actuality of this problem is proved by the enormous number of recent research works and publications [1,3,5,6,14,15,17,19,20,22]. Acoustic noise barriers are the most often used engineering solutions for reduction of the transport and industrial noise due to their advantages -relatively low cost of manufacturing and transportation, simple and fast assembling, absence of maintenance, good level of noise reduction. ...
The influence of the construction barrier thickness and profile radius upon the noise reduction in a new passive traffic noise barrier is investigated in this study. Numerical model and simulation is used after verification of the numerical procedure results using experimental setup results. Some useful conclusions about the barrier geometrical parameters design are found.
... Finally, the incidence of oblique waves onto these barriers leads to higher diffraction at the top edge and increases the noise propagation across the barrier, compared to barriers (developed in this work) that have a rough top edge. [7][8][9] The second kind of sound barriers is made of periodic structures, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and some on-road installations [ Fig. 1(a)] 29 have shown that the periodic barriers can be used to block the sound wave propagation. Some of the benefits of periodic sonic barriers include (a) a less amount of load transfer to foundation on which it is built, (b) being optically transparent and permeable to wind and (c) having an aesthetically pleasing view. ...
... Some of the benefits of periodic sonic barriers include (a) a less amount of load transfer to foundation on which it is built, (b) being optically transparent and permeable to wind and (c) having an aesthetically pleasing view. 10,11 However, one of the major drawbacks of these designs is that, with fixed periodicity, the barriers can only block traffic noise spectra corresponding to certain frequency range that is dictated by Bragg's effect. In order to elevate this problem, recent studies proposed periodic barriers that possess multi-physical phenomena properties that improve the attenuation range 11,15,17,19,23 [ Fig. 1(a)]. ...
... 10,11 However, one of the major drawbacks of these designs is that, with fixed periodicity, the barriers can only block traffic noise spectra corresponding to certain frequency range that is dictated by Bragg's effect. In order to elevate this problem, recent studies proposed periodic barriers that possess multi-physical phenomena properties that improve the attenuation range 11,15,17,19,23 [ Fig. 1(a)]. But the attenuation phenomena, such as absorption and resonance, in the modern barriers require the use of a sophisticated barrier material, and the construction process is complicated. ...
An origami sonic barrier composed of cylindrical inclusions attached onto an origami sheet is proposed. The idea allows for tunable sound blocking properties for application in attenuating complex traffic noise spectra. Folding of the underlying origami sheet transforms the periodicity of the inclusions between different Bravais lattices, viz. between a square and a hexagonal lattice, and such significant lattice re-configuration leads to drastic tuning of dispersion characteristics. The wave tuning capabilities are corroborated via performing theoretical and numerical investigations using a plane wave expansion method and an acoustic simulation package of COMSOL, while experiments are performed on a one-seventh scaled-down model of origami sonic barrier to demonstrate the lattice re-configuration between different Bravais lattices and the associated bandgap adaptability. Good sound blocking performance in the frequency range of traffic noise spectra combined with less efforts, required for actuating one-degree of freedom folding mechanism, makes the origami sonic barrier a potential candidate for mitigating complex traffic noise.
In this research, a new polyhedral geometry for a 2D unit-cell with ultrawide frequency bandgaps is proposed.
The genetic algorithm is combined with the finite element (FE) model to obtain an optimal geometry of the unitcell based on the two objective functions: (i) the largest bandgap within 0–1500 Hz and (ii) the largest bandgap
summation in the range of 0–6000 Hz. Frequency analysis is conducted for the optimized geometries to illustrate
the performance of the sonic crystal for the noise attenuation in bandgap frequencies. In order to validate the
numerical results, an experimental test for a 3D model is designed and implemented. It is shown that a strong
correlation is observed between the results from the bandgap diagram, frequency analysis, and experimental
measurements. The proposed design presents a fractional bandwidth (FB) of 80.69 % and a bandgap coverage
factor (BGCF) of 179.01 % in the applied frequency range, which are remarkable results in terms of bandgap
indexes compared to the available literature of sonic crystals. The proposed design for unit-cell represents highly
promising properties as a candidate for the noise control applications at both low and high-frequency ranges.
