Interior Noise Prediction And Control Research For Aluminum Alloy Urban Rail Vehicle

The interior noise of urban rail transit (URT) vehicle has direct influences on the passengers'riding comfortability, and is an important parameter of vehicle quality as well. The interior noise prediction can conduct car body structural design and internal acoustic space optimization by acquiring noise-produced mechanisms and sound field characteristics, so that the internal noise of car could be abated in order to satisfy the request of passengers'comfort. With the currently growing numbers of China-made parts in URT vehicle, it is being presented the momentous practical significance and applied value of the interior noise prediction and the control on car-body's design, manufacture, operation, and so on.In China the prediction research and control for URT vehicle interior noise is now just at the stage of beginning. With the lightweight demand of rail vehicle, the aluminum-alloy hollow extrusion bases have been commonly chosen as the structural materials to use on the car body of URT vehicle. In respect that current domestic researches have not conducted relevant results to cover the inner noise characteristic prediction and analysis for alloy aluminum body-framed coach, this work was specifically concentrated on the A-type aluminum alloy metro vehicles. Accordingly the analysis methods applied to automobile, the car's inner structural noise characteristic under irregular track actuation was numerically projected by the finite element method (FEM) and the boundary element method (BEM) integrated. And the interior noise properties of the coaches with same structural frames were measured to validate the predicted results at the operation sites of urban rail transportation enterprises. The further research has revealed the body structure with large proportions of interior noise by applying the acoustic transfer vector (ATV) method so that the car body's inner noise could be controlled through the structure improvement. Other approach, Zwicker Method, was be used to have the parameter computation of psychoacoustical loudness to correspond with the car's interior noise prognostication. The two appraisement methods, the A-weighted sound-pressure level and the psychoacoustical loudness, are contrasted in order to find the controlling targets of the interior noise, which are much similar to human body's psychological feeling.The whole study broadly has fulfilled the predicting analysis to the internal low-frequency structural noise of the aluminum-alloyed metro coach. The project also provides dozens of new achievements for the domestic rail vehicle's interference research, and further develops wide areas of FEM and BEM applied to the prediction of car body's interior noise. Besides, the psychoacoustical loudness-based noise parameter analysis method is used to evaluate the car's inner noise of metro. This research work represents its innovative and foreseeing, and must take a guidable function for the coming research activities of the interior noise reduction on the alloy aluminum metro and the low-noise design of body.Carefully extracting the structural features, the finite element model of aluminum alloy metro car body was established. Based on the model, the calculations of both static and dynamic parameters were furthered, and the modeled accuracy was examined. Subsequent research models were constructed, for example, the sound-field model facing car's interior space, and the systematical coupled model between body structure and internal sound field. Based on vehicle structures, acoustics and acoustic-structure coupling system modes, the mode frequency and deformation of the geometric structure, the acoustic mode frequency and sound-pressure distribution of the inner acoustic systems, as well as the changes of the mode frequency and vibrant type for the structure and the car's interior sound-field in acoustic-structure coupling systems were investigated and simulated. As a result, the analysis showed the marked correlativity between the body structure and the sound field.The kinetic analysis for the integrated metro system was performed on the established modal of vehicle-track coupled dynamic simulation. The comparisons between the car body's acceleration-oscillated simulations and the acceleration-oscillated field-tests to the homogeneous metro trains show that the results of both have rather consistent, which depicts a sound accuracy of the established dynamic simulation modal. The works make a foundation that exactly accomplishes the dynamic body-loaded simulation and computation under the random irregular track actuating oscillation.Applying the dynamic loads on the involved positions of the body structure and using the finite element harmonic response analysis method, the calculated results presented the body structure's vibration responses under the random irregular rail-track actuations. The body-structured vibration responses then was used as the boundary conditions to transfer to the boundary element models of the car's interior sound field so that it could be simulated and taken a prediction about the inner structural noise characteristics produced by the responses. The simulated results indicate that the major impact factors of internal structural noise include the property of car body structure, the status of actuating loads, and the oscillation response particularities of body walls. Comparing the interior noise's simulation results of models and the field-testing results of homogeneous metro coaches shows that the sound-pressure distributions of both are basically consistent. Moreover, all of the outcomes reflect that the car's interior noise energy mainly distributes in the range of intermediate-and low-frequency, especially having an obvious component of low frequency. Besides, the contrasting results also represent the high reliability of noise projections, or the entire simulating and computing processes are reliable. Depending on the acquired foundations, the acoustic contribution-ability analysis method alongside the application of the acoustic transfer vector (ATV) method for the car body's structure hoods gave an approach to locate places in which the considerably participative inner noise was caused by body's structural vibration, and an instruction to improve body structures. As a result, it has an evident effect on the car's interior noise reduction.As one of the ultimate productions, the particularity loudness in simulating prediction was completed by the Zwicker's computation-programmed method, and the differences of two appraisement methods, the A-level weighted sound-pressure and the loudness, had been compared. After the modification to the car body structure was done, the A-level weighted sound-pressure evaluation showed an evident entire decrease in the car's interior sound-pressure degree. However, the loudness appraisement approach indicated that the noise reduction was mainly distributed in the range below 100 Hz, while this frequency section of noise from 150 to 350 Hz, which is more sensitive to the human ears, had only relatively little attenuation. Therefore, the noise resistance should be concentrated on the noise energy reduction at the critical frequency band of Bark 1-5, so that there is an easier subjective aural feeling in the coach's sound field.The research process and final represented facts show that it is effective to predict the car body's interior low-frequency structural noise characteristics of aluminum alloy metro under random irregular rail-track actuations by combining FEM and BEM. Secondly, the ATV method is suitable to direct the improvement design for body structure to achieve the inner noise reduction. Furthermore, the psychoacoustical parameter analysis can be used to evaluate the interior noise of metro vehicle, thus to provide the noise abatement-controlled aims and improve internal sound quality of the car. The whole investigation may not pay only the scientific basis for the car-body structure low-noise design of URT vehicle, but contribute the improvement instructions for the dynamic performances of vehicle systems. In addition, the study of the project is also references to the prediction analysis and the control for the interior noise of similar car-structures.