Research On Interior Noise Control Of Medium-sized Bus In High Speed Running Condition

With the development of the automotive industry,the vehicle NVH performance require much higher.Due to the large capacity and better fuel economy,bus has been widely used in road transport.However,the impact of bus noise on passengers,especially on bus driver may lead to driver fatigue,resulting in public transport security risks.As a result,more stringent noise regulations have been enacted to limit the noise inside the bus.Meanwhile,the level of bus noise is also one of the important factors affecting its market share.In order to meet the requirement of bus factory for the strict requirements of bus noise,and take advantage of product competitiveness.Aiming at the problem of high noise in the middle speed of a medium-sized bus,the research work of vehicle interior noise control is carried out.This paper carried out the vehicle noise control research work.In this paper,a medium-sized bus is used as the research object,the noise inside and outside the vehicle is studied systematically from the noise control strategy,sound source recognition technology and noise control technology.According to the research of powertrain characteristics,road test and the stationary noise and vibration test,the noise level and noise distribution,vibration characteristics,frequency spectrum,noise propagation path have been obtained.Through the test and analysis to determine the diesel engine noise is the main source of high noise problems,clear the noise control target.From the diesel engine noise,fan noise,exhaust system noise analysis shows that the fan system is the most important noise source at high engine speed.As the fan is the most important noise source,through the cooling requirements,designed a low-noise high-performance fan,and the fan system for modal analysis,reducing the fan's first six-order natural frequency.Through the simulation of the flow field characteristics of the fan system,the pressure field and velocity field distribution of the new low noise fan are more reasonable.Based on the analysis of the sound field characteristics of the fan,the first and second noise cloud of the new design fan is obviously reduced,the first order is reduced by 16.1 dB(A),and the second order is reduced by 3.4 dB(A).The bench test of the low noise fan shows that the new design fan significantly reduces the noise at the engine high speed,has 4dB(A)improvement at 2750 rpm and improves the spectrum structure of the noise.The inside noise test results show that the bus at high speed,the driver's ear noise reduced by 3.3dB(A),the co-pilot's ear noise reduced by 3.1dB(A).Through the research of structural optimization and noise control technology and applied to the noise control of medium-sized bus,the target and strategy of noise source diagnosis and optimization are achieved at a small cost.Through the design of the new low noise and high performance fan in the premise of satisfying the cooling performance,the noise level of the vehicle is significant reduced,which solves the technical problems in the bus production and provides the support for the company to obtain the market competitive advantage.For other bus noise control provides a theoretical basis and reliable technical assurance.