Sound Quality Evaluation And Optimization For Interior Noise Of Shanghai Subway Line 9

Nowadays, rail vehicle has become a preferred way to solve urban transportation problems, due to its advantages of large carrying capacity, high speed, low energy consumption and less pollution. Subsequently, the sound quality(SQ) problem of vehicle noises has been paid more attention. Thus, how to evaluate the sound quality and control the interior noise of a rail vehicle by using finite elements methods has become a common concern in the vehicle NVH field.In this thesis, the Shanghai subway Line 9 is taken as an example. To conduct the objective evaluation of sound quality, the carriage interior noises at different operating environment and working conditions were measured on site by using the Bruel&Kjaer acoustical measurement system. Objective evaluations of the measured interior noises were performed by using the parameters of A-weighted sound pressure level(SPL), loudness, sharpness, roughness, fluctuation strength and speech articulation index, respectively. Futhermore, based on the geometric parameters of the carriage, a three-dimensional CAD model is established. Then a finite element model is obtained by using Hyper Mesh and the model is imported into the Actran software for interior sound field simulation. The feasibility and accuracy of the simulated results is verified by the experimental data. Finally, two schemes with selective sound absorption, soundproof doors and windows for interior noise reduction are put forward and performed by using orthogonal experiment method.The research results show that interior sound qualities of the Shanghai subway Line 9 are not good. The interior noise levels cannot meet the people requirement on ride comfort. There still has a large space for improvement and optimization. Comparing interior sound fields before and after the optimization, the proposed two optimization schemes reduce the interior sound pressure level by 4.81 d B and 3.25 d B and the totall loudness by 1.07 sone and 0.83 sone, respectively. And the optimizations are mainly reflected in the low and medium frequency bands, which implied a great improvement in vehicle SQ. The results indicated that the optimization schemes proposed in this thesis are feasible and effective for SQ improvement of the sample vehicle and may be extended to other types of subway vehicle, thus is beneficial for vehicle acoustical design and sound quality improvement in engineering.