Research On Low Frequency Noise In High Speed Train Under Pressure Fluctuation

The acoustic environment in the carriage of high-speed trains affects the comfort of passengers,and is also one of the factors that affect the further speed-up of high-speed trains.When CRH380 B high-speed trains are operated under three special conditions,there are large pressure fluctuations in the car.At this time,the sound environment in the car is harsh,and passengers often experience tympanic membrane compression and transient tinnitus.After the pressure fluctuation occurs in the cabin,the density of the air changes,and the density affects the response of the sound field in the cabin.To explore the influence of the pressure fluctuation on the density change of the air,the sound field response in the cabin is analyzed.In this paper,the acoustic ANSYS software is used,and the finite element method is used to study the response of the acoustic field of the acoustic cavity under different air densities.The model is subjected to modal analysis,harmonic response analysis,and transient dynamics analysis.The research shows that the first 20 order modes of the acoustic cavity model are concentrated in the low frequency range,and the low frequency noise has a greater influence on the sound field in the cabin.As the air density decreases,the modal frequency of the same order decreases,and the mode shapes are consistent.The harmonic response analysis of the high-speed train acoustic cavity model was carried out.When the noise frequency was 30 Hz,the noise excitation resonated with the car,making the response sound pressure in the car far exceeded the input excitation,which was 25 times the input sound pressure.When designing high-speed trains,the 30 Hz white noise response should be small and the design specifications of the train response.The thesis analyzes the influence of passengers ’seating position on passengers’ riding comfort.In a half-full state,in areas where no passengers are riding,the sound pressure in the cabin is greater than when there are passengers riding.The sound field under different densities is calculated and the results show that the air density decreases and the sound field in the cabin tends to increase.Compared with the pressure curve of the tympanic membrane,the pressure on the tympanic membrane of the passenger increases by 7Pa-20 Pa.