Li Li¹, Xiaopeng Fan¹, Kecheng Wu², Zhuanglei Zou¹, Yongyan Zhou¹, Dianhai Zhang^3,*, Ziyan Ren³, Yanli Zhang³

Sound & Vibration, Vol.53, No.6, pp. 251-262, 2019, DOI:10.32604/sv.2019.05252

Abstract In the current paper, which deals with the noise pollution excited by distribution transformers in the living area, a comprehensive treatment scheme is put forward for the purpose of reducing the sound pressure level emitting into the environment. In accordance with the associated test standard, the sound pressure levels of distribution transformer and surrounding environment are not only tested but analyzed as well. The measurements were carried out with the frequency analysis of the 1/3 octave resolution, with the center frequencies at 125 Hz, 250 Hz, 400 Hz, and 500 Hz. As illustrated, on the basis of the measurement results,… More >

Jcy Chen^1,*, Wc Chen¹, Tim Chen¹, Alex Wilson², N. Fadilah Jamaludin³, Nertrand Kapron¹, Tim Chen^4,5, John Burno⁵

Sound & Vibration, Vol.53, No.6, pp. 245-250, 2019, DOI:10.32604/sv.2019.04233

Abstract This paper proposes a novel artificial intelligence sythethized controller in the mechanical system which has high speed computation because of the LMI type criterion. The proposed membership functions are adopted and stabilization criterion of the closed-loop T-S fuzzy systems are obtained through a new parametrized LMI (linear matrix) inequality which is rearranged by machine learning membership functions. More >

Yixiong Yu^*

Sound & Vibration, Vol.53, No.5, pp. 237-243, 2019, DOI:10.32604/sv.2019.07887

Abstract Mining aeroengine operational data and developing fault diagnosis models for aeroengines are to avoid running aeroengines under undesired conditions. Because of the complexity of working environment and faults of aeroengines, it is unavoidable that the monitored parameters vary widely and possess larger noise levels. This paper reports the extrapolation of a diagnosis model for 20 gas path faults of a double-spool turbofan civil aeroengine. By applying support vector machine (SVM) algorithm together with genetic algorithm (GA), the fault diagnosis model is obtained from the training set that was based on the deviations of the monitored parameters superimposed with the noise… More >

J.K. Mohanty¹, A. Adarsh², P.R. Dash¹, K. Parida¹, P.K. Pradhan^1,*

Sound & Vibration, Vol.53, No.5, pp. 223-235, 2019, DOI:10.32604/sv.2019.07737

Abstract Condition monitoring is implementation of the advanced diagnostic techniques to reduce downtime and to increase the efficiency and reliability. The research is for determining the usage of advanced techniques like Vibration analysis, Oil analysis and Thermography to diagnose ensuing problems of the Plant and Machinery at an early stage and plan to take corrective and preventive actions to eliminate the forthcoming breakdown and enhancing the reliability of the system. Nowadays, the most of the industries have adopted the condition monitoring techniques as a part of support system to the basic maintenance strategies. Major condition monitoring technique they follow is Vibration… More >

Roohalah Hajizadeh¹, Ali Khavanin^2,*, Mohammad Barmar³, Ahmad Jonidi Jafari⁴, Somayeh Farhang Dehghan⁵

Sound & Vibration, Vol.53, No.5, pp. 207-222, 2019, DOI:10.32604/sv.2019.06523

Abstract Polyurethane foam as the most well-known absorbent materials has a suitable absorption coefficient only within a limited frequency range. The aim of this study was to improve the sound absorption coefficient of flexible polyurethane (PU) foam within the range of various frequencies using clay nanoparticles, polyacrylonitrile nanofibers, and polyvinylidene fluoride nanofibers. The response surface method was used to determine the effect of addition of nanofi- bers of PAN and PVDF, addition of clay nanoparticles, absorbent thickness, and air gap on the sound absorption coefficient of flexible polyurethane foam (PU) across different frequency ranges. The absorption coefficient of the samples was… More >

Cheng Hu^*

Sound & Vibration, Vol.53, No.5, pp. 199-206, 2019, DOI:10.32604/sv.2019.07712

Abstract Taking the complex mechanical systems as the research project, a theoretical multi-degree-of-freedom (MDOF) model was established. Based on the vibration characteristics analysis of this system, a novel method of vibration mitigation was proposed, which can be applied to most of the complex mechanical systems. Through this method, limited grounding stiffness was made use of and added to certain degree of freedom (DOF) discretely. Thus, the root-meansquare (RMS) of the systems amplitude can be reduced to ideal level. The MATLAB code based on this method was attached, which was tested on the theoretical model. Consider that complex mechanical systems are nonlinear… More >

Mahdi Soltanmohammadi¹, Vahid Monfared^2,*

Sound & Vibration, Vol.53, No.5, pp. 177-198, 2019, DOI:10.32604/sv.2019.05811

Abstract Dry-Type Cast Resin Distribution Transformers (CRT) is the secondgeneration of air-cooled distribution transformers where oil is replaced by resin for electrical insulation. CRT transformers may installed indoor adjacent to or near residential areas since they are clean and safe comparing to the conventional transformers. But, as it is obvious, noise discrepancy is intrinsically accompanied with all types of transformers and is inevitable for CRT transformers too. Minimization of noise level caused by such these transformers has biological and ergonomic importance. As it is known the core of transformers is the main source of the noise generation. In this paper, experimental… More >

Zhiliang Zhang, Yong Shen^*, Jie Xia, Yuchen Shen

Sound & Vibration, Vol.52, No.5, pp. 28-33, 2018, DOI:10.32604/sv.2018.03862

Abstract Since microspeakers are widely used in mobile phones, high power is usually applied to obtain sufficient output sound pressure. However, the electric power is almost converted into heat, leading to the thermal problem in microspeakers. Compared with large loudspeaker, microspeakers are smaller and the under yoke is relatively closed, causing the heat transfer more complex. In this study, a three-stage nonlinear thermal model was proposed for analyzing the thermal behavior in microspeakers. The inside air is a buffer area between the voice coil and magnet, and modeled as a middle stage of the heat transfer. The forced convection is still… More >

Ling Zhang^{1, 2}, Xiaoyan Lei¹, Jian Jiang², Qingsong Feng¹

Sound & Vibration, Vol.52, No.5, pp. 22-27, 2018, DOI:10.32604/sv.2018.04058

Abstract Underground railway vibration source strength is one of the key values used for environmental impact assessment and the evaluation of mitigation measure’s performance. However, currently there is no international standard of measuring the underground railway vibration source strength for such purposes. The available local standards and industrial guidelines do not agree on measurement locations as well as the metrics for presenting the source strength. This has caused many confusions. This paper aims to study the suitable measurement location and metrics using the data from a large scale field-testing carried out at the Nanchang underground railway (Metro Line 1, China) in… More >

Ameya M. Mahadeshwar^{1, *}, Sangram S. Patil¹, Vishwadeep C. Handikherkar¹, Vikas M. Phalle¹

Sound & Vibration, Vol.52, No.5, pp. 12-21, 2018, DOI:10.32604/sv.2018.03927

Abstract Wide range of rotating machinery contains an inherent amount of unbalance which leads to increase in the vibration level and related faults. In this work, the effect of different operating conditions viz. the unbalanced weight, radius, speed and position of the rotor disc on the unbalance in rotating machine are studied experimentally and analyzed by using Response Surface Methodology (RSM). RSM is a technique which consists of mathematical and statistical methods to develop the relationship between the inputs and outputs of a system by distinct functions. L27 Orthogonal Array (OA) was developed by using Design of Experiments (DOE) according to… More >