A Method for Reducing Noise Radiated from Structures with Vibration Absorbers by Using an Accelerated Neural Network

A method for reducing noise radiated from structures by vibration absorbers is presented. Since usual design method for the absorbers is invalid for noise reduction, the peaks of noise power in the frequency domain as cost functions are applied. Hence, the equations for obtaining optimal parameters of the absorbers become nonlinear expressions. To have the parameters, an accelerated neural network procedure has been presented. Numerical calculations have been carried out for a plate type cantilever beam with a large width, and experimental tests have been also performed for the same beam. It is clarified that the present method is valid for reducing noise radiated from structures. As for the usual design method for the absorbers, model analysis has been given, so the number of absorbers should be the same as that of the considered modes. While the nonlinear problem can be dealt with by the present method, there is no restriction on the number of absorbers or the model number.

Optimization of Vibration and Noise Performance of Permanent Magnet Synchronous Motor for Electric Vehicles

In the design of the motor used for electric vehicles(EVS),vibration and noise problems are often ignored,which reduce the reliability and service life of the motor.In this paper,an interior permanent magnet synchronous motor(IPMSM)with high power density is taken as an example,and its electromagnetic vibration and noise problem is investigated and optimized.Firstly,the factors that generate the electromagnetic force harmonic of IPMSM are analyzed by theoretical derivation.Furthermore,the mode and electromagnetic harmonic distribution of the motor are calculated and analyzed by establishing the electromagnetic-structure-sound coupling simulation model.Then,by combining finite element method(FEM)with modern optimization algorithm,an electromagnetic vibration and noise performance optimization method is proposed in the electromagnetic design stage of the motor.Finally,an IPMSM is optimized by this method for electromagnetic vibration and noise performance.The results of comparison between before and after optimization prove the feasibility of the method.

Effect of integral squeeze film damper on vibration and noise of spur gear with center-distance error

When the actual installation center distance between a pair of spur gears is greater than the theoretical center distance,backlash increases,leading to increased vibration and noise.The structural parameters of an integral squeeze film damper(ISFD)were designed with the stiffness of rigid support as reference to investigate the effect of an ISFD on the dynamic characteristics of a spur gear transmission system with center-distance installation error.A spur gear test bench with center distance-error was built to investigate the vibration and noise reduction characteristics of ISFD.The experimental results indicate that,compared with a rigid support,the ISFD can reduce vibration by approximately 40%and noise by approximately 5 d B.ISFD can effectively absorb the impact energy caused by an increase of in backlash,which is conducive to the stable operation of the spur gear transmission system.

In Situ Determination of the Effect of Drilling Noise and Vibration on Growth of Grass Carp, Myloparyngodon Piceus

The study is carried out on the effect of drilling noise and vibration on growth of grass carp, Myloparyngodon Piceus, by using cut-fin marking method in situ. Compared with other methods, the method is more appropriate, for its operation is simpler and more data may be obtained under the same condition. The results show that drilling noise and vibration have significant effect on the growth of grass carp. Critical equivalent noise and vibration grade ( Nleq and Vleq ) are about 84.4 dB and 90.2 dB, and the affecting radius is about 8.5 m. The effect of drilling noise and vibration could be influenced by some factors, such as duration of pollution and body weight of grass carp, etc. Grass carp’s growth could rapidly recover after removing drilling noise and vibration, indicating that the drilling noise and vibration do not damage the fish organs and the effect is reversible. Therefore, the effect mechanism may be due to the activating response of non-hearing system.

State Estimation for Sound and Vibration Emitted from a Machine Based on Sound Measurement Under Existenceof Background Noise

Many studies on the diagnosis for machines have become important recently because of increased use of various complex industrial systems.The correlation information between sound and vibration is very important for machine diagnosis.Usually,vibration pickups are attached directly to the machine in order to measure vibration data.However,in some cases,the sensors can not be attached directly on highly precise devices.In this study,a method to estimate the fluctuation of sound and vibration is proposed based on the measurement data of sound emitted from the machine under existence of background noise.The effectiveness of the proposed theory is experimentally confirmed by applying it to the observed data emitted from a rotational machine driven by an electric motor.

Prediction and Reduction of StructureBorne Noise in Vehicle

The structure and the acoustic medium of a passenger vehicle are modeled using the finite element method(FEM), and the interior noise is studied the help of the modal synthesis method (MSM). Sound pressure level (Lp) of the noise is calculated in several conditions of the models, and has good agreements with its test results. The MSM am be consequently used for predicting the vehicle interior noise in dssign stage so that the structure may be optimized for the Purpose of the most reduction of noise.

Common-mode noise rejection using fringe-locking method in WEP test by simultaneous dual-species atom interferometers

We theoretically investigate the application of the fringe-locking method（FLM） in the dual-species quantum test of the weak equivalence principle（WEP）.With the FLM,the measurement is performed invariably at the midfringe,and the extraction of the phase shift for atom interferometers is linearized.For the simultaneous interferometers,this linearization enables a good common-mode rejection of vibration noise,which is usually the main limit for high precision WEP tests of the dual-species kind.We note that this method also allows for an unbiased determination of the gravity accelerations difference,which meanwhile is ready to be implemented.

Railway ground vibration and mitigation measures: benchmarking of best practices

Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their resi-dents.Among the different sources,the one coming from the rail transit system will play a central concern in the following years due to its sustainability.Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry.This paper aims to describe and compare the different mitigation systems existing and reported in liter-ature through a comprehensive state of the art analysis providing the performance of each measure.First,an introduction to the ground-borne vibration and noise gen-erated from the wheel-rail contact and its propagation through the transmission path is presented.Then,the impact and the different ways of evaluating and assessing these effects are presented,and the insertion loss indicator is introduced.Next,the different mitigation measures at different levels(vehicle,track,transmission path and receiver)are discussed by describing their possible appli-cation and their efficiency in terms of insertion loss.Finally,a summary with inputs of how it is possible to address the future of mitigation systems is reported.

Optimization Design of Vibration Characteristics of Ship Composite Brace with Rigid Vibration Isolation Mass

In considering the theory of structural dynamic optimization design, a design method of the structural style of ship composite brace with rigid vibration isolation mass was studied. Two kinds of structural dynamic optimization formulations minimizing the vibration acceleration of the non-pressure hull on the restraining condition of the gross weight of the ship cabin were established: 1) dynamic optimization of the sectional dimensions of the rigid vibration isolation mass in the composite brace; 2) dynamic optimization of the arranging position of the rigid vibration isolation mass. Through the optimization results, sectional dimensions and the arranging position of the rigid vibration isolation mass with better performance in reducing vibration were gained, and some reference was provided for practical engineering designs as well as enrichment of the design method of a novel ship vibration-isolation brace.

Study on the Impediment to Vibration Wave Propagation from Rigid Vibration Isolation Mass

Based on the principle of impedance mismatching,the performance of rigid vibration isolation mass in impeding vibration wave propagation was discussed from the perspective of wave approach.Based on FEM,the influence of its weight as well as the cross-section shape parameters on the isolation performance of rigid vibration isolation mass was studied through numerical simulation.The results show that rigid vibration isolation mass can effectively impede the propagation of the medium and high frequency vibration waves,and the heavier the vibration isolation mass,the better the isolation performance.For low frequency waves,the vibration isolation effect is not so obvious;for a rectangular vibration isolation mass,the isolation performance could be effectively improved by increasing the cross-section height and reducing the cross-section width.A useful reference was provided for the application of rigid vibration isolation masses to the vibration isolation and noise reduction of ship structure.

A new mechanism for friction-induced vibration and noise

For years,friction-induced vibration and noise(FIVN)has puzzled many researchers in academia and industry.Several mechanisms have been proposed for explaining its occurrence and quantifying its frequencies,notably for automotive brake squeal,clutch squeal,and even rail corrugation.However,due to the complex and complicated nature of FIVN,there is not yet one fundamental mechanism that can explain all phenomena of FIVN.Based on experimental results obtained on a simple test structure and corresponding numerical validation using both complex eigenvalue analysis(CEA)and transient dynamic analysis(TDA),this study attempts to propose a new fundamental mechanism for FIVN,which is the repeated cycles of partial detachment and then reattachment of the contact surfaces.Since friction is ubiquitous and FIVN is very common,the insight into FIVN reported in this paper is highly significant and will help establish effective means to control FIVN in engineering and daily life.

Vibration and Noise Optimization of New Asymmetric Modular PMaSynRM

An optimized structure to weaken the vibration and noise of a new asymmetric permanent magnet-assisted synchronous reluctance motor(PMaSynRM)is proposed.The new asymmetric PMaSynRM has the advantages of a low torque ripple and high fault tolerance.However,the asymmetric structure generates an unbalanced magnetic force(UMF),which results in vibration and noise problems.In this study,the vibration and noise of the motor are analyzed and optimized.First,the radial pressure is analyzed,and an optimized structure is proposed.The electromagnetic performance of the motor before and after optimization is analyzed using the finite element method.Second,a three-dimensional model is established,and modal analysis is conducted considering the orthotropy of the stator and effective windings.Finally,the vibration and noise are simulated and analyzed,and the validity of the analysis results is verified experimentally.The analysis results indicate that the optimized motor realizes a reduction in the motor vibration and noise.

车内噪声主动控制发展综述及其在实车上的应用

本文对小型轿车车内噪声分布及其声源进行了分析,对国内外研究者对噪声主动控制研究成果的发展历程作了综述,并介绍了噪声主动控制理论及模型,最后结合具体实车,介绍了目前应用在实车上的车内噪声主动控制范例。

Fast Calculation of Electromagnetic Forces in IPMSMs Under PWM VSI Supply Based on Small-Signal Time-Harmonic Finite Element Method

This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection,quantification,and prediction of damages.Early detection of faults may allow the downtime of maintenance to be rescheduled,thus preventing sudden shutdown of machines.In cylinder pressure developed,vibrations and noise emissions data provide a rich source of information about condition of engines.Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue.The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines.The effects of changing various fuel injection parameters was analyzed.Scope of using non-intrusive technique has been analyzed by changing locations of microphone.Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up.Various frequency ranges of contributing noise and vibration sources were identified.Time-Frequency analysis showed the onset of various cyclic.Based on the identification of various frequency bands,it is possible to device suitable filters in order to extract more information.

Research on Influence of Damping Material on Structure Performance of Torpedo

Reducing the self-noise and radiated noise of torpedo is an effective way to enhance its detection and concealment capabilities.After discussing the basic principle on noise and vibration control and main noise sources in torpedo,the application of damping treatment for noise and vibration absorption was proposed in this paper.Compared composite materials(damping and metal materials)used as segment joint,their different contributions to the damping performance of base structure were investigated.The results show that the damping material can be used as segment joint effectively in vibration control.Taking cantilever beam as an example,four different damping treatments were compared in natural frequency and damping loss factor,the results show the influences of different damping layer layouts on the structure damping performance,and offer a reference for the torpedo shell design.

INCE PUBLISHES BERANEK ’S NOISE AND VIBRATION CONTROL

A Revised Edition of the now-classical 1971 text edited by L.Beranek,Noise and Vibration Control,has been published by the Institute of NoiseControl Engineering.Noise and Vibration Control is of great value to designand safety engineers,consultants,scientists,architects,governmentresearchers,public officials and others concerned with the control of noiseemitted by machinery and with control of environmental noise in buildings,in the workplace,near airports and highways,and in the community.This

Technical note：Large amplitude free vibration of a flexible panel coupled with a leaking cavity

This paper addresses the effect of leakage on the natural frequencies of a large amplitude vibrating panel backed by a cavity, which has not been considered in many other related studies. The structural-acoustic governing equations are employed to study this nonlinear problem. An elliptical integral method, which was recently developed for the nonlinear panel cavity problem, is introduced here to solve for the structural-acoustics responses. The present results agree reasonably well with those obtained from the classical harmonic balance method. Modal convergences of the nonlinear solutions are performed to verify the proposed method. The effects of vibration amplitude and leakage size are studied and discussed. It is found that （1） the edge leakages in a panel cavity system significantly affect the natural frequency properties, and （2） the edge leakages induce a low frequency acoustic resonance.

Thermal optimization and experimental research of high-speed universal pulverizer

Because of high efficiency, energy conservation,simple operation, wide application range, and small size,the high-speed universal pulverizer has been well receivedby customers. However, its electrical motor can overheatwhen working, which hinders continuous operation of thepulverizer. In this study, a series of efforts were made toaddress this problem. Firstly, a detailed analysis of theworking principle of the pulverizer was conducted and anoptimization plan was proposed, consisting in punchingventilation holes on the surface of the original pulverizer.Simulations of the pulverizer flow field before and afteroptimization were performed. The hydrodynamic simula-tion results were used to conduct a steady state thermalanalysis of the pulverizer, investigating the influence of theflow field on heat transfer. Additionally, experimentalinvestigations were conducted on the pulverizer before andafter optimization in order to measure and compare theparameters （motor working temperature, wind speed andtemperature of the motor cooling system, vibration, noise,and pulverizing degree of the material） influencing theperformance of the pulverizer. The numerical simulationresults showed an increment in heat transfer caused byincrement in air flow volume and velocity when air wasinjected into the pulverizer through bottom and side holes.Experimental results showed that the pulverizer with airinjection through holes had the best performance whentemperature, vibration, and refinement effect were consid-ered as performance indicators.

Characterization of Automotive Brake Discs with Laser-Machined Surfaces

In the automotive and transport industry,braking noise and vibrations are persisting issues and difficult to control.Automo-tive engineers and researchers are putting considerable effort into overcoming these problems,and significant breakthroughs have been made in this area.In this study,M-shaped grooves were bionically designed and manufactured on the frictional surfaces of four automotive brake discs using a laser machine.Various tests were conducted to characterize the physical and mechanical performance of the modified discs along with their noise and vibration responses.The experimental results demonstrate that discs with laser-machined grooved surfaces have better surface hardness and residual stress reduction than discs with un-grooved surfaces.Significant improvement in the braking performance was observed in terms of disc thickness variation,friction and wear,noise,and vibration reduction.It is concluded that the reduction in braking noise and vibrations is mainly caused by the reduction in the coefficient of friction and wear,increase in damping ratio,and improvement of disc thickness variation of the brake disc by laser surface grooving.