Rail Roughness Acceptance Criterion Based on Metro Interior Noise

Severe rail roughness leads to a series of problems in metro systems,particularly the vehicle noise problem.To ensure a better acoustic environment,rail roughness control is therefore one of the main concerns for the metro operators.But the existing roughness acceptance criteria are not suitable for metro interior noise control.It is an appropriate method to determine the rail roughness limit based on interior noise.A rail roughness acceptance criterion based on metro interior noise is accordingly proposed in this paper.The relationship between rail roughness and interior noise can be derived with wheel-rail noise as link.With this objective,a combined test and simulation method is adopted.A validated wheel-rfigil noise prediction model is thus established to determine the relationship between rail roughness and wheel-rail noise.Moreover,the transfer function of wheel-rail noise to interior noise is developed based on extensive field test.Using this method,the noise sensitivity to roughness wavelength and acceptance criteria at different speeds and track structures are investigated.Finally,an eclectic rail corrugation acceptance criterion on curved track is suggested in consideration of practical application.

An investigation into high-speed train interior noise with operational transfer path analysis method

Passengers’demands for riding comfort have been getting higher and higher as the high-speed railway develops.Scientific methods to analyze the interior noise of the high-speed train are needed and the operational transfer path analysis(OTPA)method provides a theoretical basis and guidance for the noise control of the train and overcomes the shortcomings of the traditional method,which has high test efficiency and can be carried out during the working state of the targeted machine.The OTPA model is established from the aspects of“path reference point-target point”and“sound source reference point-target point”.As for the mechanism of the noise transmission path,an assumption is made that the direct sound propagation is ignored,and the symmetric sound source and the symmetric path are merged.Using the operational test data and the OTPA method,combined with the results of spherical array sound source identification,the path contribution and sound source contribution of the interior noise are analyzed,respectively,from aspects of the total value and spectrum.The results show that the OTPA conforms to the calculation results of the spherical array sound source identification.At low speed,the contribution of the floor path and the contribution of the bogie sources are dominant.When the speed is greater than 300 km/h,the contribution of the roof path is dominant.Moreover,for the carriage with a pantograph,the lifted pantograph is an obvious source.The noise from the exterior sources of the train transfer into the interior mainly through the form of structural excitation,and the contribution of air excitation is non-significant.Certain analyses of train parts provide guides for the interior noise control.

Active Noise Control of the Heavy Truck Interior Cab

In order to control the noise of the heavy truck interior cab effectively, the active noise control methods are employed. First, an interior noise field test for the heavy truck is performed, and frequencies of interior noise of this vehicle are analyzed. According to the spectrum analysis of acquired noise signal, it is found out that the main frequencies of interior noise are less than 800Hz. Then the least squares lattice （LSL） algorithm is used as signal processing algorithm of the controller and a closed-loop control DSP system, based on TMS 320VC5416, is developed. The residual signal at driver＇s ear is used as feedback signal. Lastly, the developed ANC system is loaded into the heavy truck cab, and controlling the noise at driver＇ s ear for that truck at different driving speeds is attempted. The noise control test results indicate that the cab interior noise is reduced averagely by 0.9 dBA at different driving speeds.

Adaptive Multi-Feature Fusion for Vehicle Micro-Motor Noise Recognition Considering Auditory Perception

The deployment of vehicle micro-motors has witnessed an expansion owing to the progression in electrification and intelligent technologies.However,some micro-motors may exhibit design deficiencies,component wear,assembly errors,and other imperfections that may arise during the design or manufacturing phases.Conse-quently,these micro-motors might generate anomalous noises during their operation,consequently exerting a substantial adverse influence on the overall comfort of drivers and passengers.Automobile micro-motors exhibit a diverse array of structural variations,consequently leading to the manifestation of a multitude of distinctive auditory irregularities.To address the identification of diverse forms of abnormal noise,this research presents a novel approach rooted in the utilization of vibro-acoustic fusion-convolutional neural network(VAF-CNN).This method entails the deployment of distinct network branches,each serving to capture disparate features from the multi-sensor data,all the while considering the auditory perception traits inherent in the human auditory sys-tem.The intermediary layer integrates the concept of adaptive weighting of multi-sensor features,thus affording a calibration mechanism for the features hailing from multiple sensors,thereby enabling a further refinement of features within the branch network.For optimal model efficacy,a feature fusion mechanism is implemented in the concluding layer.To substantiate the efficacy of the proposed approach,this paper initially employs an augmented data methodology inspired by modified SpecAugment,applied to the dataset of abnormal noise sam-ples,encompassing scenarios both with and without in-vehicle interior noise.This serves to mitigate the issue of limited sample availability.Subsequent comparative evaluations are executed,contrasting the performance of the model founded upon single-sensor data against other feature fusion models reliant on multi-sensor data.The experimental results substantiate that the suggested methodology yields heightened recognition accuracy and greater resilience against interference.Moreover,it holds notable practical significance in the engineering domain,as it furnishes valuable support for the targeted management of noise emanating from vehicle micro-motors.

Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations:Ⅰ.Production mechanisms of the noise

Applying the wavenumber frequency transfer function to describe the whole system including tht elastic cylindrical shell and the fluid loading, a general expression of the cross spectrum of the interior noise induced by the TBL (turbulent boundary layer) pressure fiuctuations is derived. There are two production mechanisms of the noise: one is direct transfer of the convective ridge of the pressure fluctuations through the shell, the other is the reradiation of resonance modes excited by the pressure fluctuations. At low frequencies the noise produced by the latter mechanism is dominant. Solving the frequency equation of the cylindrical shell with liquid loading, the two Stoneley-type poles in the complex K plane are presented. They are the major sources of the reradiation of shell at low frequencies. Finally, effects of the shell radius, shell thickness, absorption of material and the flow speeds on the noise reduction are computed by numerical iniegration.

Active control of interior noise within an irregular enclosure under the cooperation of point force and Incident wave

A new modeling method is developed for the active control of interior noise within an irregular three-dimensional cavity under the cooperation of point force and incident wave. The validity of this method is verified by a regular cuboid enclosure. With global and local performance functions, good results are obtained in the active control of noise within the irregular enclosure according to numerical investigations.

Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations:Ⅱ. finite hydrophone and array

Finite hydrophone and hydrophone array are the wave vector filter and can re-duce the flow noise. In this paper the responses of the cylindrical area hydrophone and two-circular area hydrophone within viscoelastic cylindrical shell to the TBL (turbulent boundary layer) pressure fluctuations are investigated. Applying the method based on the wavenumber frequency spectrum analysis, the expressions of 1) the noise power spectrum of a single hy-drophone; 2) the space correlation of two hydrophones; 3) the noise power spectrum of array are derived. The dependencies of the noise reduction on hydrophone shape, dimension, element amount and separation of hydrophones of array are calculated by numerical integration. The wide-band and narrow-band correlation for two hydrophones is also calculated. The numerical results show that hydrophone array can effectively reduce the interior noise.

Simulation on a Car Interior Aerodynamic Noise Control Based on Statistical Energy Analysis

How to simulate interior aerodynamic noise accurately is an important question of a car interior noise reduction. The unsteady aerodynamic pressure on body surfaces is proved to be the key effect factor of car interior aerodynamic noise control in high frequency on high speed. In this paper, a detail statistical energy analysis （SEA） model is built. And the vibra-acoustic power inputs are loaded on the model for the valid result of car interior noise analysis. The model is the solid foundation for further optimization on car interior noise control. After the most sensitive subsystems for the power contribution to car interior noise are pointed by SEA comprehensive analysis, the sound pressure level of car interior aerodynamic noise can be reduced by improving their sound and damping characteristics. The further vehicle testing results show that it is available to improve the interior acoustic performance by using detailed SEA model, which comprised by more than 80 subsystems, with the unsteady aerodynamic pressure calculation on body surfaces and the materials improvement of sound/damping properties. It is able to acquire more than 2 dB reduction on the central frequency in the spectrum over 800 Hz. The proposed optimization method can be looked as a reference of car interior aerodynamic noise control by the detail SEA model integrated unsteady computational fluid dynamics （CFD） and sensitivity analysis of acoustic contribution.

Noise levels inside the coaches of Greater Cairo tunnel metro, line 3 tunnel

This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo.The study focuses on the effects of alignment profiles on the A-weighted noise level.Although the latest line has not been studied yet,noise levels inside the old lines attracted the attention of researchers due to their importance as the first mass transit system in Africa.Given that windows are usually kept open,measurements were conducted inside the empty cabin at the end of the train with open windows according to ISO 3381:2005.Results showed that noise emissions inside the running coaches are high and do not follow either international or general national legislation,which presents health hazards for drivers and commuters.Speech intelligibility is required for train radio units and driver consoles for voice communications,which provides a safe working environment for the train crew.The present study reveals that tight curves mainly contribute to high noise.The noise levels are further raised by the reflective surface of the tunnel with a circular cross-section and the unballasted track.Moreover,the noise level is affected by the location of the coach and window conditions(open/close)to some extent.