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Muffler with circular section and inner symmetric acoustical elements has been habitually used in industry. In order to improve the acoustical performance, an advanced eccentric muffler having ellipse cross-section, multiple chambers, and multi-segment perforated/non-perforated tubes is presented. Concerning about high order wave effect to the muffler, a finite element method (FEM) run on COMSOL package is adopted. In addition, the influence of sound transmission loss with respect to various geometric parameters has been explored. In order to simplify the optimization process, a simplified objective function established by an Artificial Neural Network (ANN) and FEM has been implemented and connected to a Genetic Algorithm (GA). Two case studies of muffler optimization for two kinds of design parameter sets (one of Lin and Lout and the other of Lin1 and Lout 1) are introduced. Two targeted frequencies (1000 Hz and 2500 Hz) are selected and applied in the two cases’ muffler optimization. Simulated results reveal that the acoustical influence relating to various geometric parameters is huge. The sound attenuation will increase in the low frequency region if the curvature ratio δ (ratio of long axis to short axis in ellipse) or the X (horizontal length of the muffler’s body) increases. Consequently, the study demonstrates a methodology in the optimization of a four-chamber ellipse and eccentric muffler internally inserted with multi-segment perforated/non-perforated tubes.

Because of high pressure impulse noise emitted from the outlet of pneumatic equipment, an appropriate noise abatement device installed at the top of a venting outlet is compulsory. However, a given known noise reduction using a bronze-made sintered porous plug at the venting outlet is insufficient. An exploration of advanced noise reducing device is required. In this paper, three kinds of mufflers (Muffler A: with part AA (a bronze-made sintered porous inlet); Muffler B: with part BB (a casing with expansion cones and extended perforated/non-perforated tubes); and Muffler C: part AA (a bronze-made sintered porous inlet) + part BB (a casing with expansion cones and extended perforated/non-perforated tubes)) have been introduced and acoustically analyzed. To assist the optimization of mufflers composing of complicated acoustical mechanism, a finite element method using finite element method (run on COMSOL) together with a simplified objective function model and Genetic Algorithm (GA) is presented. Here, the simplified model of objective function is established by means of Artificial Neural Networks (ANNs). In addition, three kinds of frequencies, including one low frequency (500 Hz) and two high frequencies (3000 Hz, and 5000 Hz), have been chosen as the target frequencies during the muffler C’s optimization process. Consequently, considering a space-constrained situation, an optimally shaped muffler using both parameters D and L is efficiently accomplished within space-constraint situation.

Because venting noise emitted from high pressure valve often occurred in industry and is huge, the noise abatement of the venting noise to protect human’s hearing health is necessary. In order to depress the high speed noise, a muffler internally equipped with spiral perforated tube is presented. To mitigate this noise, a dissipative muffler with perforated spiral tube installed on the pipeline is proposed. To evaluate the acoustical performance, a finite element method using COMSOL software is adopted. Also, the sensitivity analyses of Transmission Loss (TL) of the proposed muffler with respect to (1) diameter of the spiral and perforated tube ( D), (2) pitch of the spiral tube ( L), (3) acoustical impedance of the dissipative acoustic material ( R), and (4) perforation rate of a perforated tube (σ) has been carried out. For the optimization studies, both Artificial Neural Network (ANN) and Genetic Algorithm (GA) to optimize the muffler parameters L and D are applied. Here, two high target frequencies (2000 and 3500 Hz) to optimize the proposed muffler are exemplified. Consequently, the hybrid design of perforated spiral tube optimized using ANN and GA will mitigate the high pressure valve noise efficiently.

This paper aims to eliminate the pneumatic noise using a muffler hybridized with a metal sintered bronzed porous material, a spiral tube, and expansion cones. In this paper three kinds of mufflers (Muffler A: with part AA (a bronze-made sintered porous inlet); Muffler B: with part BB (a casing with a spiral tube and expansion cones); and Muffler C: part AA (a bronze-made sintered porous inlet) + part BB (a casing with a spiral tube and expansion cones)) have been introduced. A finite element method run on the COMSOL software will be adopted in the acoustical analysis of the mufflers. The influence of TL with respect to two kinds of design parameters (QQ: the number of expansion cone; σ1: the acoustical flowing impedance of the acoustical wool) has been assessed. Simulated results reveal that the muffler C with acoustical components of AA and BB is superior to the other two mufflers. Moreover, the design parameters of QQ and σ1 have essential acoustical influence to the muffler C.

Enormous effort has been applied to research on mufflers hybridized with a single perforated plug tube; nonetheless, mufflers conjugated with multiple parallel perforated plug tubes that disperse venting fluid and reduce secondary noise have been overlooked. To this end, an analysis of the sound transmission loss of two-chamber mufflers with multiple parallel perforated plug tubes that are optimally designed to perform within a limited space will be presented. Here, using a decoupled numerical method, a four-pole system matrix for evaluating acoustic performance (sound transmission loss) is derived. During the optimization process, a simulated annealing method, which is a robust scheme utilized to search for the global optimum by imitating a physical annealing process, is used. Prior to dealing with a broadband noise, the sound transmission loss’s maximization relative to a one-tone noise (200 Hz) is produced to check the simulated annealing method’s reliability. The mathematical model is also confirmed for accuracy. To understand the acoustical effects brought about by the various tubes (perforated tubes, internally extended non-perforated tubes, and non-perforated tubes), mufflers with internally extended non-perforated tubes and non-perforated tubes have been evaluated. The optimization of three kinds of two-chamber mufflers hybridized with one, two, and four perforated plug tubes have also been compared. The results are revealing: the acoustical performance of mufflers conjugated with more perforated plug tubes decreases as a result of the decrement of the acoustical function for acoustical elements (II) and (III). Accordingly, in order to design a better muffler, an advanced presetting of the maximum (allowable) flowing velocity is necessary before an appropriate number of perforated plug tubes can be chosen for the optimization process.

A reciprocating compressor is commonly used in industry. However, because it is extremely noisy and harmful to the ears, a noise control mechanism is necessary. Eight kinds of noise control strategies used with the reciprocating compressor are explored, and COMSOL, a numerical analysis software, is adopted for acoustical analysis in the paper. The primary purpose of this research is to assess the influence of seven noise control strategies for the suction/discharge muffler of a reciprocating compressor. Results have shown that the noise control strategies can efficiently improve the acoustical performance of the suction/discharge mufflers.

Presently, there is a trend to design larger capacity hard disks that have a faster revolving speed and a precise mechanism. However, because of external vibrations, these are highly sensitive to data transmission. Therefore, vibration control on hard disks is crucially important. In this paper, a traditional hard disk is placed on a vibration testing device. Data transmission efficiency for the disk will be detected via IOmeter software. Here, the influence of a traditional hard disk's data transmission with respect to external forces (various vibration accelerations), revolving speeds, tilted angles, hardness and thickness of damping material, and material property will be experimentally assessed. Results reveal that a slight tilted angle will result in better data transmission. In addition, the hardness of the hard disk plays an essential role in reducing the vibrational impact on the data transmission. Also, data transmission in the damping material of the shoe cushion will be more efficient than that of a pneumatic cushion. Moreover, the data transmission will decrease when the rotating speed of the disk increases. Consequently, the thickness of the damping material will influence the data transmission even though the hardness is fixed.

Presently, there existed in industrial plants broadband noise hybridized with pure tones. In order to overcome a pure tone noise with a high peak value that is harmful to human hearing, a traditional reactive muffler has been used. However, the traditional method for designing a reactive muffler has proven to be time-consuming and insufficient. Helmholtz mufflers that deal with a pure tone have been adequately researched. However, manufacturing costs for the Helmholtz resonator have been too expensive. Noise elimination of pure tones for side-branched resonators (SBRs) that are easily manufactured has also been addressed. Nevertheless, the shape optimization of multi-chamber side-branched mufflers that deal with a broadband noise hybridized with multiple tones has been mostly ignored. In order to efficiently reduce the peak noise level, interest in shape optimization of a side-branched muffler is coming to the forefront. That being so, an analysis of the sound transmission loss ( STL) and the best optimized design for a hybrid side-branched muffler under a space-constrained situation will be considered, here. Concerning the plane wave effect, the theoretical acoustic performance of a multi-tone hybrid side-branched muffler will be established using a four-pole system matrix. A numerical case for eliminating broadband noise hybridized with two tones emitted from a machine room using eight kinds of mufflers (muffler B–I) will also be introduced. To find the best acoustical performance of a space-constrained muffler, a numerical assessment using a simulated annealing ( SA) method is adopted. To verify the availability of the SA optimization, a numerical optimization of muffler A at a pure tone (600 Hz) is exemplified. Before the SA operation can be carried out, the accuracy of the mathematical model has been checked using the experimental data. Moreover, the influences of the sound transmission loss (STL) with respect to n-series SBRs and the STL with respect to m-parallel SBRs have also been assessed. Also, the influence of the STL with respect to the design parameters such as the section area (Sb) of the SBR, the height (ZH) of the SBR, and the section area (S) of the main duct has been analyzed. Results reveal that the peak values of the pure tones are efficiently reduced after the hybrid side-branched muffler is added. Moreover, the acoustical performance of the hybrid side-branched muffler will increase when the number (m) of the parallel SBRs increases. Consequently, a successful approach in eliminating a broadband noise hybridized with two pure tones using optimally shaped hybrid mufflers and a simulated annealing method within a constrained space has been demonstrated.

There has been much research on partitioned plenums in the industrial field. However, maximum noise reduction of a plenum within a constrained space, which frequently occurs in engineering problems, has been neglected. Therefore, the optimum design of multi-chamber plenums becomes essential. In this paper, five-chamber plenums intersected by four baffles within a fixed space are assessed. In order to select the appropriate design parameter sets used in the shape optimization of a five-chamber plenum, three kinds of design parameter sets (Case I: L1* and L2*; Case II: L1** and L2**; Case III: L1***, L2***, and L3***) are proposed. In order to simplify the shape optimization of plenums intersected by multiple baffles, a simplified objective function (OBJ) is established by linking the boundary element model (BEM, developed using SYSNOISE) with a polynomial neural network fitted with a series of real data - input design data (baffle dimensions) and output data approximated by BEM data in advance. Before optimization is performed, accuracy of the boundary element method (BEM) for a one-chamber and three-chamber plenum is checked using analytical and experimental data and found to be accurate. To assess the optimal plenums, a genetic algorithm (GA) is adopted. Consequently, optimal results reveal that the depths of the two upper baffles and the two lower baffles play essential roles in minimizing the noise level of the lower frequencies (400∼800 Hz). Moreover, the horizontal span of the baffles will influence the acoustical performance of the higher frequencies (1200 Hz and above).

Recently, research on new techniques of single-chamber mufflers hybridized with an internal extended tube has been addressed; however, the research work on space-constrained multi-chamber mufflers conjugated with multiple internal extended tubes which may increase the acoustical performance within a specified back pressure has been neglected. Therefore, the main purpose of this paper is not only to analyze the sound transmission loss (STL) of a space-constrained tube-extended muffler equipped with 1∼3 chambers but also optimize the best design shape under a specified pressure drop. In this paper, the four-pole system matrix for evaluating acoustic performance – sound transmission loss (STL) – is derived. Moreover, a particle swarm optimization (PSO), a robust scheme used to search for the global optimum by imitating bird flocking or fish schooling behavior to achieve a self-evolving system, has been used during the optimization process. Before dealing with a broadband noise, the STL's maximization with respect to a one-tone noise is introduced for a reliability check on the PSO method. Additionally, an accuracy check of the mathematical model is performed. To appreciate the acoustical ability of the internal extended tubes and chambers inside a muffler, three kinds of multi-chamber mufflers hybridized with extended tubes (one-chamber, two-chamber, and three-chamber mufflers) have been assessed and compared. Results reveal that the maximal STL is precisely located at the desired tone. Consequently, a successful approach used for the optimal design of the tube-extended mufflers equipped with 1∼3 chambers under space and back pressure constrained conditions has been demonstrated.

Noise control is essential in an enclosed machine room where the noise level is regulated by the occupational safety and health act. In order to overcome noise hybridized by a direct and reverberant sound wave, a sound absorber in conjunction with an acoustical enclosure has been used. However, the traditional method for designing a sound absorber and an acoustical enclosure has proven to be time-consuming. In order to efficiently control the noise level specified by the Environmental Protection Agency, interest in shape optimization of a sound absorber as well as acoustical enclosure is coming to the forefront. In this paper, the numerical technique of particle swarm optimization ( PSO) in conjunction with the theoretical sound propagation model and the method of minimized variation square are applied in the following numerical optimizations. Before noise abatement is carried out, the accuracy of the mathematical model in a single-noise enclosed system will be checked by SoundPlan (a professional simulation package). Moreover, the noise abatement of five kinds of multi-equipment machine rooms using the PSO method has been exemplified and fully explored. The results reveal that both the acoustical panel and the acoustical enclosure can be precisely designed. Consequently, this paper may provide an efficient and rapid way of depressing both the direct and reflected sound wave by using a well-designed acoustical panel and acoustical enclosure in a complicated sound field.

Although research in finding optimal muffler shapes for low-frequencies noise using reactive mufflers has already been addressed, research into shape optimization of hybrid mufflers that reduce broadband noise within a constrained pressure-drop backpressure is lacking. Therefore, the shape optimization of four kinds of hybrid mufflers using simulated annealing ( SA) in conjunction with the generalized decoupling technique and plane wave theory are presented. Here, a numerical case in eliminating nitrogen venting noise is introduced. The reliability of the SA optimization is also verified using the optimization of muffler A for a pure tone. Moreover, the accuracy of the mathematical models is acceptable with minor deviations between the theoretical and experimental data. Results reveal that the higher backpressure limit will result in a higher acoustical performance. Consequently, the acoustical performance for a hybrid muffler equipped with multiple reactive chambers and one dissipative chamber is superior to that of reactive mufflers.

Because high noise levels in industrial plants can be injurious to workers and lead not only to psychological but also to physiological ailments, noise control in factories becomes essential. In order to overcome the noise impact emitted from a multi-noise plant, a sound barrier, a popular noise control strategy, has been used in the industrial field for a long time. Yet, the traditional method in the design of a sound barrier is time-consuming. Recently, to economically improve acoustical performance, a new strategy (flexible allocation) is applied; however, the acoustical performance is still insufficient. In order to quickly, efficiently, and economically control the noise level specified by the Environmental Protection Administration, interest in shape optimization of a sound barrier in conjunction with equipment allocation around the plant's boundary is rising. In this paper, the novel technique of simulated annealing (SA) in conjunction with the theoretical sound propagation model and the method of minimized variation square is applied in the following numerical optimizations. Before a sound barrier is optimized, the sound propagation from one single noise is tested and compared with the experimental data for the purpose of accuracy within the mathematical model. Moreover, three kinds of sound barrier systems have been fully discussed and optimally shaped by the SA. The results reveal that the sound barrier can be properly shaped. Consequently, this paper may provide an efficient and rapid methodology in the shape-optimized work for a sound barrier installed in a multi-equipment plant.

An optimization of a layout plan and noise reduction on multi-noises system is considered. In this paper, a novel approach, a genetic algorithm (GA) based on the principles of natural biological evolution, is used as an optimizer. [1] By GA optimization in adjusting the locations and the required noise reduction for each piece of noisy equipment, the deviation with respect to the targeted noise value along the system's boundary line specified by EPA (Environment Protection Authority) can thus be minimized. In addition, the techniques of binary genetic algorithms (BGA), reproduction, crossover mutation and elitism are applied in GA searching. The numerical cases of multi-noise systems are exemplified. Results show that the correctness of the GA method is acceptable. The optimal design of noise control by adjusting the location and choosing the proper noise reduction measures on equipment proposed in this study offers a quick and economic approach.