This paper presents an investigation into the characteristics of interior noise of a Chinese high-speed train under several typical conditions. Interior noises within Vehicle TC01, which can be used as a head car or a...This paper presents an investigation into the characteristics of interior noise of a Chinese high-speed train under several typical conditions. Interior noises within Vehicle TC01, which can be used as a head car or an end car, and Vehicle TP03, the third car counting from TC01, are measured for the train running at speeds from 260 km/h to 385 km/h, along two types of track including a slab track and a ballast track and either on the ground surface or in a tunnel. Data analyses are performed for sound pressure overall levels, frequency, area contributions, and possible generation mechanisms, showing how they are affected by train speed, running direction, track type, and tunnel. The results show that, whether TC01 is used as head car or end car, the interior noise characteristics in the VIP cabin are mostly related to aerodynamic noise. Differences in interior noise between tracks become smaller as the train speed increases. The effect of a tunnel on the interior noise is more important for the middle coach than that for the head coach. This study can provide a basis for noise control of high-speed trains.展开更多
Theoretical analysis and experimental measurement of pulse-width fitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is ded...Theoretical analysis and experimental measurement of pulse-width fitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced. The power spectra with and without pulse-width fitter are that the pulse-width jitter will contribute considerably numerically simulated. The simulation results indicate noise to the pulse power spectrum while the product of pulse width and angular frequency is larger than 1. The experimental measurement of pulse-width fitter of a gain-switched Fabry-Perot laser diode with 2.4 GHz repetition rate is also reported. In comparison of the noise power spectra of the first, fourth and seventh harmonics of the pulse repetition rate, 2.3ps pulse-width jitter is obtained.展开更多
The acoustical character of low noise asphalt pavement was studied theoretically and experimentally. Its normal incident absorption coefficient can reach 0.5 - 0.7, much better than that of general asphalt pavement, ...The acoustical character of low noise asphalt pavement was studied theoretically and experimentally. Its normal incident absorption coefficient can reach 0.5 - 0.7, much better than that of general asphalt pavement, although both are the same in thickness and maximum aggregate size. The connected porosity is the most major parameter, which can control the coefficient. The more the porosity is, the higher the coefficient is. The peak value of normal incident absorption coefficient will increase and move towards lower frequency when the depth of pavement is thickened. The peak will approach a stable value when the depth is about 40 mm. The measurement results show that the traffic noise can reduce 4 dB - 8 dB at a test low noise asphalt pavement when a car speed is more than 60 km·h-1展开更多
基金Project supported by the National Natural Science Foundation of China （Nos. 51475390 and U 1434201）, the National Key Technology R＆D Program of China （Nos. 2016YFB1200506-08 and 2016YFB1200503-02）, and the Scientific Research Foundation of State Key Laboratory of Traction Power （No. 2015TPL_T08）, China
文摘This paper presents an investigation into the characteristics of interior noise of a Chinese high-speed train under several typical conditions. Interior noises within Vehicle TC01, which can be used as a head car or an end car, and Vehicle TP03, the third car counting from TC01, are measured for the train running at speeds from 260 km/h to 385 km/h, along two types of track including a slab track and a ballast track and either on the ground surface or in a tunnel. Data analyses are performed for sound pressure overall levels, frequency, area contributions, and possible generation mechanisms, showing how they are affected by train speed, running direction, track type, and tunnel. The results show that, whether TC01 is used as head car or end car, the interior noise characteristics in the VIP cabin are mostly related to aerodynamic noise. Differences in interior noise between tracks become smaller as the train speed increases. The effect of a tunnel on the interior noise is more important for the middle coach than that for the head coach. This study can provide a basis for noise control of high-speed trains.
基金Supported by the National Natural Science Foundation of China under Grant No 60577019, and the Scientific Research Foun- dation （SRF） for the Returned 0verseas Chinese Scholars （R0CS）, State Education Ministry （SEM） under Grant No 20521017002.
文摘Theoretical analysis and experimental measurement of pulse-width fitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced. The power spectra with and without pulse-width fitter are that the pulse-width jitter will contribute considerably numerically simulated. The simulation results indicate noise to the pulse power spectrum while the product of pulse width and angular frequency is larger than 1. The experimental measurement of pulse-width fitter of a gain-switched Fabry-Perot laser diode with 2.4 GHz repetition rate is also reported. In comparison of the noise power spectra of the first, fourth and seventh harmonics of the pulse repetition rate, 2.3ps pulse-width jitter is obtained.
文摘The acoustical character of low noise asphalt pavement was studied theoretically and experimentally. Its normal incident absorption coefficient can reach 0.5 - 0.7, much better than that of general asphalt pavement, although both are the same in thickness and maximum aggregate size. The connected porosity is the most major parameter, which can control the coefficient. The more the porosity is, the higher the coefficient is. The peak value of normal incident absorption coefficient will increase and move towards lower frequency when the depth of pavement is thickened. The peak will approach a stable value when the depth is about 40 mm. The measurement results show that the traffic noise can reduce 4 dB - 8 dB at a test low noise asphalt pavement when a car speed is more than 60 km·h-1
