Study On Interior Noise Of Gangway And Sound Insulation Optimization Of Windshield In High-speed Trains

The internal windshield is one of the weakest segment for high-speed trains,the gangway area also has the highest noise level of the interior noise,which in turn affects the interior noise level of gangway.Therefore,it is of great significance to study the interior noise of the internal windshield and the sound insulation characteristics of the internal windshield for controlling the interior noise.In this paper,aiming at the interior noise control of the gangway area and optimization design of the internal windshield,the following research works are mainly carried out:(1)The research progress and current situation of the interior noise of gangway and the sound insulation of car body at home and abroad are summarized.The necessity and possibility research directions of the interior noise of gangway area and the sound insulation of internal windshield are discussed.(2)Based on the field test,the interior noise characteristics of gangway are analyzed,the overall value,the spectrum characteristics and the distribution of the interior noise are obtained.Tests of the interior noise of the gangway are made under different conidtions,such as running speeds,track types and operating mileage,based on these test data,variation laws of the interior noise of the gangway area to these factors are obtained.The main focusing frequency band of the sound insulation design of the internal windshield will change from the 1/3 octave band of 800 Hz to 160 Hz as the train speed increases.For the ballastless track in an open-line condition,the main focousing frequency band of the sound insulation design is located in the1/3 octave band of 400~1000 Hz,but for the ballast track,the main focusing frequencies are loacted in the 1/3 octave band of 100~315 Hz;compared with the open-line operating condition,the main focusing frequency is located in the 1/3 octave band of 500~1000 Hz;the wheel irregulatity will be developed with the increasing of the operating mileage,of which can cause the significant frequency to the 1/3 octave band of 500~1000 Hz.Therefore,the 1/3octave band of 630 Hz need to pay extremely attentions when considering the maintainlity of the interior noise level of the internal windshield area in condition of lifecycle.(3)Based on the statistical energy analysis(SEA)method,the prediction model of interior noise of internal windshield area is established,the model is validated by the interior noise field test.Based on the validated model,the effects of the amplitude of the excitation sources,the sound insulation and the gap between of the gangway are analyzed,the acoustic sensitivities of the interior noise of the internal windshield to the key acoustic parameters are obtained.The sensitivity of the interior noise of the gangway to the excitation source amplitude(±3 dBA variable),internal windshield sound insulation(±3 dB variable)and equivalent leakage area of internal windshield(2~8 mm~2 variable)is 0.9,-0.8 and 0.2 dB/mm~2,respectively.(4)Based on the focusing frequency range of the interior noise of the gangway area and the acoustic sensitivity to the sound insulation of the internal windshield,the acoustic optimization design of the interior windshield is carried out.Firstly,based on SEA method,the prediction model of the sound insulation of the internal windshield is established,the model is validated by sound insulation laboratory test.Secondly,the effects of the structure,material properties and sound absorption treatment of the internal windshield on the performance of the sound insulation are compared and analyzed,increasing the material thickness on the sound insulation performance has the most significant effects to the performance of the sound insulation.Finally,the mapping relationship between the interior noise of the gangway area and the parameters of structure and material is established,and a low interior noise design of the windshield structure is proposed.The noise reduction effect of the low noise windshield structure to the interior noise of the gangway is evaluated,results show that it can reduce 6.3 dBA at 350 km/h.The above research can provide a theoretical guidance for the low noise design of the interior noise of the gangway.