摩托车噪声源识别分析（本科毕业论文设计）.doc

摘 要

摩托车噪声是评价摩托车等级水平的重要指标之一，降噪已成为国内外各摩托车生产厂家亟待解决的重要课题。而根据噪声的声学特性，摩托车噪声主要取决于最大噪声源的大小，因此准确识别噪声源就成了降低摩托车噪声的前提。
本文首先从理论上介绍了摩托车噪声产生的机理，由于摩托车的噪声中发动机噪声占很大比重，所以重点对发动机噪声进行了阐述，包括机械噪声、空气动力噪声、燃烧噪声和表面辐射噪声。随后，本文介绍了噪声源识别的几种常用方法，并描述了各种方法的工作原理及其各自的适用范围，重点阐述了声强法。
结合本课题的内容及现有条件，确定用近场声强法作为此次实验的测量方法，实验是在发动机台架上进行的，并把频率分为低、中、高三个频段分别进行分析，通过声功率排序，最终确定了发动机气缸、曲轴箱外壳、排气管为主要噪声源，并且确定声源的频率分布；随后进行时间功率谱阵分析确定了在1000Hz左右发生共振，而这都为确定降噪措施提供依据。本文的最后还进行了一次验证实验，通过改进前后的实验对比，确定降噪措施是否有效。


关键词：摩托车噪声，近场声强测量，声功率，时间功率谱阵













ABSTRACT

Noise level is one of the most assessment indicators to eva luate motorcycle, and now the noise reduction becomes a major issue that needs the domestic and foreign manufacturers to solve urgently. Based on the acoustic characteristic of noise, the noise of motorcycle is depends on the main sound sources, that means noise reduction of motorcycle is on the premise that the identification of the sound sources is accurate.
Firstly，this paper introduces the mechanism how the motorcycle’s noise produced , and because of the motorcycle’s noise mainly coming from the engine, the focus is the noise of engine , including the mechanical noise, aerodynamic noise , burner noise and radiation noise from the surface. Subsequently, this paper introduces several commonly used methods of the sound source identification, and describes the operating principle and the applicability of each method, focusing on the elaboration of the sound intensity method.
And considering the content of this subject and the existing condition, finally the author chooses the near field phonometry as the measuring method, this experiment is operated on the engine bench, and the total frequency band is divided into low, middle and high band and there is a analysis that separately based on each band, after the collation of the sound power , the main sound sources have been found ,they are cylinder, crankcase enclosure and exhaust pipe, and also there are frequency allocations of each sound source . Subsequently, based on the analysis of time-power spectrum array, we find 1000Hz is a resonance frequency, and all of these provide the basis to noise reduction measure. At the end of this paper, there is a confirmatory measurement, comparing the measurement results, one of which is gained before the improvement and another is after the improvement, to check whether this measure is effective.


Key words：noise of motorcycle, near-field sound intensity measurement, sound power, time-power spectrum array


目 录

中文摘要 Ⅰ
ABSTRACT Ⅱ
1绪论 1
1.1 引言 1
1.2 摩托车噪声源识别的重要性及意义 1
1.3 国内外研究现状 1
1.4 本课题的研究内容及目的 1
2 摩托车噪声产生的机理 1
2.1 空气动力噪声 1
2.1.1 进气噪声 1
2.1.2 排气噪声 2
2.2 燃烧噪声 3
2.3 机械噪声 1
2.3.1 活塞对缸套的敲击噪声 1
2.3.2 配气机构噪声 2
2.3.3 传动齿轮噪声 1
2.3.4 滚动轴承噪声 2
2.4 发动机的表面噪声 3
3 噪声源识别的方法 1
3.1 声强测量法 1
3.1.1 声强测量法的理论依据 1
3.1.2 声强测量原理框图 2
3.1.3 声强测量在主要噪声源识别中的应用 2
3.2 其他几种方法 1
3.2.1 频率分析法 1
3.2.2 分别运行法 2
3.2.3 铅覆盖法 1
3.2.4 表面振动速度（加速度）法 2
3.3 数字信号分析方法 3
4 摩托车噪声源识别实验及结果分析 1
4.1 实验介绍 1
4.1.1 实验装置 1
4.1.2 测点布置 2
4.2 声强测量结果及分析 1
4.2.1 前端面测量分析 1
4.2.2 左侧面测量分析 2
4.2.3 右侧面测量分析 1
4.2.4 顶面测量分析 2
4.2.5 消声器右侧面测量分析 2
4.2.6 总结 2
4.3 时间功率谱阵分析 3
4.3.1 梁平机场实验测得 2
4.3.2 国检中心实验测得 2
5 改进前后实验分析 1
5.1 实验介绍 1
5.1.1 实验装置 1
5.1.2 测点布置 2
5.2 实验数据及分析 1
5.2.1 改进前右侧曲轴箱外壳表面的声强测量分析 1
5.2.2改进后右侧曲轴箱外壳表面的声强测量分析 2
5.3 小结 3
5.4 实验注意事项 3
6 结论 1
致谢 1
参考文献