External noise characteristics analysis of straddle-type monorail transit based on field tests

Compared with the traditional urban rail transit system, the running mechanism, line laying structure and operating environment condition of straddle-type monorail transit are unique. Therefore, external noise radiated by the train has its own characteristics when the train is running. In order to improve the acoustic quality and explore the methods of noise reduction, it is necessary to carry out field test and understand its radiation characteristics. In this study, typical running lines of straddle-type monorail transit are selected for multi-state and multi-site field tests of external noise of the running train. The test conditions include straight line running state, curve line running state, slope line running state, entry and exit station state. The obtained time data are post-processed in timefrequency domain, and then the radiation characteristics of external noise are analyzed in detail. The time domain characteristic is mainly discussed based on the overall level of external noise of the running train. In frequency domain, the contributions of the sound pressure energy (CSPE) of 1/3 octave bands under each running state of the train are analyzed, and the effects of straddle-type monorail traffic noise and urban road noise on urban transportation noise are evaluated using energy contribution analysis method. Finally, the main noise sources are briefly identified and analyzed. The research results will be helpful to provide meaningful reference for noise reduction and control.