Abstract: A sample bus abnormally vibrates with noise when it runs at 90 km/h. It seriously deteriorates the vehicle’s NVH performance. In this paper, the time tracking of vibration frequency is done under the condition of the 5-th speed acceleration to find out the possible excitation source. The three-dimensional spectrum diagram shows that the main vibration scenarios and noise frequencies inside the bus are similar to those of the 1st and 2nd order rotation frequencies of the transmission shaft. Then, the structure of the transmission shaft is improved by strengthening the support of the shaft, adding rubber isolators and improving the suspension frame. As a result, the vibration and noise level of the entire vehicle is significantly reduced. The analysis and the test method shown in this paper provide a reference for vibration and noise reduction of vehicles.

Key words: acoustics, excitation, NVH, spectrum analysis, rotation frequency

摘要： 某款轻型客车样车在90 km/h左右速度行驶时，车厢地板出现剧烈振动并伴随共鸣噪声，严重影响汽车NVH性能。通过试验手段，在五档加速工况对振动频率进行时间跟踪，找到可能的激励源。从三维频谱图识别出车内主要振动和噪声频率与传动轴的1阶和2阶转动频率相同。对此进行加强传动轴支架，支架加橡胶垫和改换悬置为进口悬置的改进。由此可使整车振动噪声水平大幅度降低。

关键词: 声学, 激励源, NVH, 频谱分析, 转动频率