Noise Absorber Research Articles

Deformation and Fracture Behavior of Sandwiched Copper Foam Brazed Joint Using Amorphous Copper–Tin–Nickel–Phosphorus Filler

Utilization of open-cell metal foams in functional applications such as in energy absorption, noise absorber, heat insulator, and lightweight panels is trending in many industrial applications. The development of reliable joining technologies for sandwiched metal foams is crucial for thermal application and one of the techniques used is brazing process. In the current work, copper foam was sandwiched between a copper plate using amorphous filler of Cu-9.7Sn-5.7Ni-7.0P (Cu: copper, Sn: tin, Ni: nickel, and P: phosphorus) via brazing technique. The shear test was conducted on the brazed joint interface of copper/copper foam, while the compressive test was carried out on the brazed sample. Microstructures of the copper substrate surface obtained from the shear fracture of brazed copper/copper foam show the tear region and cleavage fractures. The stress–strain curve of shear and compressive strength explains the deformation behavior of the brazed sample.

Sound Prohibited Zone for Smart Cities using IoT

One of the dominant causes of noise pollution is the disruptive honking while traveling on a road and is particularly problematic as well as resulting in irritating sound. This results in many effects that need to be addressed taking into consideration stress, depression, mental and physical illnesses. The proposed system comprises of an embedded module that will be of great benefit to citizens of society adjacent to heavily populated roads, students studying in schools near crowded roads, patients admitted to roadside hospitals, etc. Noise Armor's alternative approach needs immense expenditure and personnel for both repair and surveillance as there is the need for expensive noise absorbers. By developing a real-time (smart) honking device that automatically allows vehicles on the road to reduce the volume of horn near conscious areas such as schools , hospitals, old-age homes, baby care centers and other organizations that are adversely damaged, our research aims to develop an effective solution for excessive honking.

An experiment on different type of muffler on spark Ignition engine 110 cc performance

The design of the exhaust system affects many parameters such as reducing the noise level, control velocity, temperature, back-pressure of exhaust gas and reduce pollution production. The exhaust system has many parts which consist of an exhaust manifold, resonator, catalytic converter, muffler, and connecting pipes. Muffler has the main function as a noise absorber. Furthermore, the temperature distribution on mufflers is also affected by fuel consumption by reducing back-pressure effect. This study has conducted an experiment to determine the effect of modified muffler shape in a motorcycle which consists of standard, scorpion, and 3v3 type. The effects of mufflers’ performance on the motorcycle are described on torque and power graphics. Furthermore, this study explains the muffler geometry effect on noise reduction from the combustion process. The installation of 3v3 muffler decreases torque and power in a motorcycle. Moreover, the installation of 3v3 muffler type raises noise pollution level which generates by the engine combustion process.

Cultivation of prospective plant seeds for Almaty city greening

This Abstract. One of the most pressing problems of human society is the impersonality of urban spaces, of which green spaces are an integral part. Plants in an urbanized environment are not only a source of oxygen, noise and gas absorbers, etc., but also an element that unites and connects diverse residential buildings. This raises the question of the self-identification of urban spaces. Problems include a meager assortment, the absence or presence in a single specimen of promising species that are not sufficiently stable in an urban environment. This article discusses the determination of seed productivity in laboratory conditions of plantsOriganum vulgarecollected from Ile Alatau of Kazakhstan and Berberis iliensis Popov collected from the Ile river of Almaty region. Laboratory experiments have shown high germination ofOriganum vulgareand Berberis iliensis seeds, but the germination of seeds collected from different populations is different: for example,Origanum vulgareand Berberis iliensis plants had the highest laboratory germination of № 2 seeds.Origanum vulgareon the seventh day of growth reached 40% in population №1, 44% in population №2 and 41% in population №3. Laboratory productivity for 25 days of growth was 91% in population №1, 95% in population №2, and 87% in population №3. The maximum validity of Berberis iliensis seeds in the second population is 92.5%, and the lowest is 63% suitable for the first population.

NOISE-ABSORBING ACOUSTIC SCREEN BASED ON A HELMHOLTZ RESONATOR

The paper aims at studying the noise protection potential of an acoustic screen based on a Helmholtz resonator to solve the problem of noise reduction level in the area in front of the screen. For experimental analysis, a modular acoustic screen has been made. Replaceable modules are made on the basis of a wooden frame with stiffening ribs, one side of the module is blind, another has slotted holes, which ensures the formation of noise absorbers on a Helmholtz resonator principle. Changing the position of the modules in the support racks provides the ability to change the screen reflexive surface nature. The main problem solved in this work is to experimentally determine the decrease magnitude in the sound pressure level in the area in front of the screen. The results of sound pressure level measurements at various frequencies are provided, the comparison of the reflected noise obtained values with the results obtained in the sound pressure level analysis in the case of a solid screen is given. The coincidence of the calculated values of the active sound absorption frequencies with the measured values is shown. It is concluded that there is a possibility to solve the nose reduction level problem when using such screens in areas where people can be.

Aerogel two ways: Towards ultralight noise absorbers

Aerogels are a class of synthetic materials that are derived by using supercritical drying to extract the liquid component of a gel and replacing it with gas. This process results in the formation of an ultra-lightweight nanoporous solid composed of up to 99.98% air by volume. In this talk, we explore the possibility of developing aerogel-based ultralightweight sound absorbers in two different forms. First, we focus on the acoustic characterization of aerogel granules. The absorption properties of four different aerogels with granule diameters ranging from 2 to 4000 μm and granule densities ranging 120 to 180 kg/m3 are presented. Next, we discuss the additive manufacturing of aerogel-based sound absorbers using a freeze casting method. This novel method allows the fabrication of solid aerogel structures with controlled microstructural properties. The sound absorption and transmission loss properties of 3-D printed aerogel samples are measured using an impedance tube setup. We demonstrate that such structures can provide significantly higher absorption and transmission loss properties as compared with current passive noise reduction materials. [Work Sponsored by NASA EPSCoR.]

Evaluation of Noise Absorption Capacity of Various Materials

Noise absorption and transmission property of materials is of great importance in order to determine the amount of noise transmitted from source to receiver. Unwanted noise can cause various biological and psychological effects to humans and other organisms in nature. This paper deals with the experimental study on noise absorbing and deflecting ability of various available materials. These materials could be utilized in industrial complexes and building construction applications for noise level reduction purposes. The materials such as glass, plywood, thermocol (scientifically known as polystyrene), fiber plastic sheet and coconut fiber sheet have been used in the experiment as a noise barrier. Through experimental analysis, the reduction noise level was obtained in terms of decibel (dB), sound power level and loss of sound energy using hand held noise analyzer. The finding suggests that thermocol has the best sound absorbing capacity at medium to low sound pressure levels, whereas glass has the best sound absorbing capacity at high sound pressure levels.

Synergy between Noise Reduction Techniques Applied in Different Industries: A Review

This review aims to assist aerodynamic noise in three industrial fields: Aerospace, Turbomachinery and Automotive. In this review the general terms in aeroacoustics is defined; and aerodynamic noise sources are recognized. The paper also reviews the brief literature on noise reduction techniques, with a particular focus on the state of the art numerical and experimental works. In Addition, developments in low speed designs for aerodynamic noise reduction, some passive and active methods for example serrated boundaries, porous media, noise absorber, and etc. are discussed. By investigating similarities in noise reduction techniques between these industries, this paper offers an outlook for noise reduction techniques in future.

A new feedforward hybrid active control system for attenuating multi-frequency noise with bursty interference

Noise from rotating machinery in an enclosed space exhibits both narrowband and broadband characteristics. Hybrid active noise control (HANC) algorithms are usually used in this case to cancel both kinds of noise. However, sometimes also bursty noise occurs. In a mechanical system, for example, it may occur in every cycle if the gear wheel faces are damaged. Bursty noise has high amplitudes and short duration, and this may deteriorate the narrowband attenuation performance of the HANC method. To address this problem, a feedforward HANC algorithm with a sinusoidal residual error structure (HANC-SRE) is proposed in this paper. By applying the sinusoidal residual error (SRE) subsystem, the proposed HANC-SRE algorithm can decrease the error interference between different narrowband adaptive filters for different frequencies. The structure of the traditional HANC is then redesigned to use the broadband filter as the primary noise absorber and the narrowband filters as secondary ones to achieve better performance for bursty noise. Moreover, we also introduce a variable step-size updating method to improve the tracking performance of the system. Theoretical analysis of convergence conditions and instantaneous residual output error is performed to evaluate the performance of the HANC-SRE algorithm. Experimental results demonstrate that HANC-SRE achieves better tracking performance while also being more robust than conventional HANC methods.

Optical, acoustic and thermal performance assessment of semi-transparent amorphous silicon PV glazing systems

In this research, a unique PV glazing technology, thermally resistive PV glazing (TRPVG), is introduced, and its thermal, optical and acoustic performance parameters are experimentally investigated. In the previous works, multifunctional benefits of TRPVG as a novel building element such as high thermal resistance, promising electricity generation potential, self-cleaning and competitive cost are addressed. Within the scope of the present research, absorption of UVC and UVA part of incoming sunlight, control of visible light transmittance and solar thermal radiation, reduction of different noise levels, and temperature difference across the PV glazing are comprehensively analysed. The tests are conducted in April 2019 for a specific sample (TRPVG-Ar16) in which a 16 mm thick argon is utilised as inert gas behind a-Si PV cells for thermal resistance, and a novel low-e coated thermally resistive glass is reinforced at the rear. The results reveal that TRPVG-Ar16 is a very good thermal insulator at first glance. The average temperature difference between front and back surfaces is determined to be 16.59 oC, which is promising and a strong function of incoming solar radiation. The average solar radiation is measured to be 527.6 W/m2 during the test period, and the aforesaid value behind the PV glazing is found to be 41.6 W/m2. A similar tendency is observed for the visible light transmittance. Average light intensity measurements from the front and back of TRPVG-Ar16 are reported to be 622.3 and 75.4 Lux, respectively. UVC and UVA measurements reveal that the novel TRPVG-Ar16 technology is capable of blocking 100% of UV part of incoming sunlight, which needs to be noted. The tests carried out for various noise levels also demonstrate that TRPVG-Ar16 is a promising noise absorber. Outside the simulation environment, the noise level is measured to be 84.3 dBA while it is 56.5 dBA for the indoor, which corresponds to about 33% reduction in dBA value.

Mechanism of stiffness reduction in a thin broadband noise absorber

Sound absorption by fibrous material is often considered broadband but poor in performance when the frequency is low. A new absorber is considered thin or otherwise when its thickness is compared with such a fibrous absorber for a given performance requirement. The performance of the latter is poor due to air stiffness in a compact design. This study first introduces a composite structure based on a parallel array of resonators with or without fibrous filling. The array is shown to introduce equivalent negative stiffness which is accompanied by a surge in system damping derived from resonator coupling. In principle, high damping is required for optimal absorption when the system as a whole is not operating at its resonance. However, the frequency dependency of such a composite system is too complex to be exactly optimal. The performance of the array structure is compared with a new fibrous absorber embedded with mass made from impervious membranes. The bandwidth and other characters of the two absorbers are compared when the incident sound has the typical environmental noise spectrum. Conclusions are shown to contradict with a few widespread misconceptions.

Estudio del comportamiento de los morteros reciclados frente al ruido de impacto

En la actualidad existe una amplia gama de sistemas y materiales que se emplean como atenuadores del ruido de impacto, ofreciendo buenas prestaciones a la hora de evitar la transmisión de vibraciones a través de los forjados. En este trabajo, se han elaborado placas de mortero de cuatro centímetros de espesor con cuatro tipos de árido diferentes combinados con distintas tipologías de aislamiento. Aprovechando la menor densidad de los morteros elaborados con árido reciclado, se ha llevado a cabo una investigación en la que se propone sustituir el 100% del árido natural por árido reciclado para la fabricación de morteros empleados en el sistema de losa flotante, ya que ofrecen una solución más eficiente desde el punto de vista acústico. Los morteros elaborados con áridos reciclados de cerámica y mixto los que presentan la solución óptima para atenuar impactos producidos sobre la superficie, reduciendo hasta en un 20% la velocidad de transmisión de impactos frente a sus homólogos elaborados con árido natural.

Effects of Secondary Leakage Inductance on the LLC Resonant Converter

It is quite often to utilize the transformer leakage inductance in the resonant tank of the LLC resonant converter to allow for a drastic reduction in the converter cost, weight, size, and volume. The effects of the secondary leakage inductance on the operation of the LLC resonant converter are not well discussed in the relevant literature, and it is the purpose of this paper to give an insight into these effects. The contribution of this paper lies in the following: first, highlighting that it is not always an accurate assumption to consider that the values of the primary and secondary leakage inductance are identical, specifically in asymmetric magnetic core structures. Second, it has been disclosed that the well-known coupling factor ( k 12) cannot properly express the unequalized leakage inductance distribution in the proposed asymmetric transformer. Therefore, the authors bring the primary coupling factor ( k 1) and secondary coupling factor ( k 2) into practice to appropriately express the unequalized leakage distribution on the primary and secondary windings, which can be controlled by the allocation of the relevant winding with respect to the air gap, utilizing the noise absorber, and changing the distance between the winding. Several transformer prototypes had been built and experimentally tested to validate these hypotheses. Third, it has been observed that the transformer voltage gain and efficiency can be improved when the transformer leakage inductance is concentrated on the secondary side to avoid the voltage drop inflicted by the relatively large value of the magnetizing current $(i_{m})$ , especially at the light load condition. Fourth, it has been reported that in a transformer structure with a concentrated value of leakage on the secondary side would decrease the resonant tank input impedance, vertically widen the voltage–gain curve of the converter, and eventually increase the frequency control bandwidth with respect to the load variation. Transformer prototypes had been constructed and tested in a 390 V/12 V–220 W LLC resonant converter to evaluate the proposed analysis.

Application of Box Behnken Design to Optimize the Parameters for Kenaf-Epoxy as Noise Absorber

This journal discusses the application of Box Behnken design to plot the experiments to find the Noise Absorption Coefficient (NAC) for Kenaf/Epoxy sandwich sample with an overall objective of optimizing the density, thickness, pressure and frequency. Response Surface Methodology (RSM) has been embraced to express the yield parameters (reactions) that are chosen by the input procedure parameters. RSM likewise evaluates the connection between the variable input parameters and the comparing yield parameters. The proposed Box-Behnken configuration requires 24 trial of run for information securing and displaying the reaction surface. Software’s were utilized to plan the examination and randomize the runs. Regression model was created and its capability was checked to foresee the yield esteems at about all conditions. Facilitate the model was approved by performing tests, taking 24 sets of inputs. The yield parameters estimated through tests (actual) are in great match with the anticipated esteems utilizing the model. Utilizing Design Expert software, 2D and 3D plots were produced for the RSM evolved. This research resulted in ascertaining the optimised set of noise absorber parameters for Kenaf/Epoxy sandwich sample, to get the optimum NAC. This work gains significance in the sense with minimum number of experiments, reliable model has been generated, validated and further, the process has been optimised and mathematical equation generated.

Transmission Attenuation Power Ratio Analysis of Flexible Electromagnetic Absorber Sheets Combined with a Metal Layer.

Electromagnetic noise absorber sheets have become a solution for solving complex electromagnetic interference (EMI) problems due to their high magnetic losses. This contribution is focused on characterizing a novel structure that is based on an absorber film with a metal layer attached on its top side. Two different absorber compositions were combined with Al and Cu metal layers in order to study the improvement on the performance of these structures, depending on the complex permeability, absorber film thickness, and type of metal. The transmission attenuation power ratio of the absorber films is analyzed and compared to the performance of absorber and metal structures. The measurement procedure is carried out attaching the films into a microstrip line that has been designed based on IEC standard (IEC 62333-2). This test fixture is employed as a transmission line to simulate a general noise path. The performance of absorber composites to filter electromagnetic noise is evaluated through analyzing S21 and S11 parameters. This is carried out with the aim of finding out in which conditions the absorption loss is improved when a metal layer is attached. In addition, the possible re-radiation effect, due to the magnetic field that is generated by the eddy currents induced in the metal layer, is examined.

Evaluasi Tingkat Kebisingan Kawasan Selatan Universitas Negeri Padang

This study aims to determine and evaluate the level of noise in the southern area of Universitas Negeri Padang (UNP) Kampus Air Tawar conducted at 23 points of measurement with 16 outside outdoor points and 7 indoor measurement points. Method of measurement under regulation of Indonesian government, KepMenLH Regulation no. 48 thn 1996 which regulate the noise level standard by using SLM (Sound Level Meter). The highest outdoor noise level occurs in front of GOR UNP (S16) at the time of L3 which is 80,91 dBA, while the highest indoor noise level when there was activity as well as no activity in the room was happened in lecture hall FBSS UNP (S7-interior) with value equal to 83, 99 dBA and 64.65 dBA. All points of a total of 16 outdoor and 7 indoor measurement points exceed the standard noise level threshold which is 55 dBA (+3 dB tolerance). However, from the questionnaire results most respondents just feel slightly disturbed by outdoor noise in the study area. The noise control that can be done such as cultivate number of natural vegetation such as heliconia sp, tea, acacia tree and pringgodani bamboo, also the installation of continuous wall from type of clear fiber that serves as building noise absorbers.

Karakteristik Akustik Panel Serat Aren dengan Bahan Perekat Latex

This research was intended to study the acoustical characteristics of acoustic panel made from Aren fiber and Latex. The samples were produced by mixing aren fiber and latex with 90/10, 85/15, 80/20, 75/25 and 70/30 of weight percentage ratios, respectively. The measurements were conducted by using Impedance Tube Method. The result show that acoustic panels made from aren fiber and latex are good noise absorber. The best absorption was performed by sample made of 90/10 fiber and latex, with noise absorption coefficient 0f 0.95 at 3000 Hz.

Design and Performance of Hybrid Arrays of Mo/Au Bilayer Transition-Edge Sensors

For future X-ray astrophysics missions, X-ray microcalorimeters can be optimized with different properties in different regions of the focal plane. This approach has the potential to improve microcalorimeter instrument capabilities with efficient use of instrument resources. For example a point-source array optimized for high angular resolution, high count-rate observations could be accompanied by a main array to expand the field of view for diffuse observations. In this approach, it is desirable to be able to simultaneously optimize different transition-edge sensor (TES) geometries on a single wafer design. The key properties of TESs such as transition temperature and shape are a strong function of size and geometry due to the complex interplay between the proximity effect from the superconducting bias electrodes and the normal metal features used for noise suppression and absorber contact. As a result, devices fabricated with the same deposited layer but with different sizes will have different transition temperatures and different response to X-ray events. In this paper, we present measurements of the transition temperature and properties of devices with different sizes and normal metal features, and discuss how by tuning the geometry we can achieve the desired pixel parameters for a given application. We also describe measurements of transition properties from large-format hybrid arrays containing three different pixel types.

Impedance approach to designing efficient vibration energy absorbers

The concept introduced previously by the authors on the best sound absorber having the maximum allowable efficiency in absorbing the energy of an incident sound field has been extended to arbitrary linear elastic media and structures. Analytic relations have been found for the input impedance characteristics that the best vibrational energy absorber should have. The implementation of these relations is the basis of the proposed impedance method of designing efficient vibration and noise absorbers. We present the results of a laboratory experiment that confirms the validity of the obtained theoretical relations, and we construct the simplest best vibration absorber. We also calculate the parameters and demonstrate the efficiency of a dynamic vibration absorber as the best absorber.

Laboratory test and FEM analysis on a developed continuous rail absorber (CRA)

Rail has a significant contribution in overall produced noise in railway freight tracks. Implementing rail noise absorbers is a promising way to increase the attenuation of the vibration. Designing of a rail noise absorber to work in critical frequencies in which the rail undergoes its maximum vibration is crucial. Moreover, total cost of installation, maintenance, repair, and operations as practical aspects of manufacturing have drew the attention of researchers. Regard to this point, the authors have developed a continuous rail noise absorber (CRA) which is composed of steel and elastomeric layers. The lateral and bottom surfaces of the rail is covered by the layers using specialized proprietary adhesive. The initial investigations and survey of the problem is reported in the authors’ previous paper which resulted in proposition of CRA. In this research CRA is produced and laboratory tests are carried out on a disjointed section of Tehran-Zanjan commercial rail track to determine the efficiency of the noise absorber system. It is revealed that the noise of rail availed of CRA is decreased about 9 dB in frequency range 500-2000 Hz. Owing to its noncomplex structure and lower cost of installation, CRA is a desirable noise absorber system for railway administrations. Furthermore, experimental values are compared with those ones obtained through a finite element model which are in a good agreement.