大客车降噪的研究

运用噪声分离、频谱分析等技术手段，找出了GZ6921型后置柴油机大客车噪声超过国家标准的原因，并对主要噪声源及其频谱分布进行了分析对各主要噪声源－排气系统、冷却系统和发动机舱采取相应的降噪措施，如降低风扇转速，改善抗性消声器的降噪能力，修改冷却风进风道，平衡车两侧的噪声源，在发动机舱中粘贴吸音材料等。改进后GZ6921型大客车最大加速度时的车外噪声由91．5dB(A)降到86dB（A)以下，达到国际GB1495－75“机动车允许噪声”的规定。

A Study on Bus Noise Reduction

In this Paper,noise separation and frequency spectrum analyzingtechniques are used to find out why the noise level of the bus of GZ6921 model with rear-placed diesel engine layout exceeds the limit set by the national standard,the nain noise sources and their frequency spectrum distribution are thus identified.Noise reduction measures which are aimed at the main noise sources such as the exhaust system,the cooling air-intake system and the engine cabin are applied,including slowing down the fan's rotation speed,enhancing noise reduction ability of the acoustic-reactive type muffler,modifying the shape of cooling air-intake path,balancing noise in both sides of the bus and adopting sound-absorber in the engine cabin.After these treatments,outside noise level of the bus with maximum acceleration declines from 91.5 dB(A) to lower than 86 dB(A),which meets the "permitted Noise Level of Motor Vehicle"defined by the “GB 1495-79”national standard.