摘 要

摩托車噪聲是評價摩托車等級水平的重要指標之一，降噪已成為國內(nèi)外各摩托車生產(chǎn)廠家亟待解決的重要課題。而根據(jù)噪聲的聲學特性，摩托車噪聲主要取決于最大噪聲源的大小，因此準確識別噪聲源就成了降低摩托車噪聲的前提。
本文首先從理論上介紹了摩托車噪聲產(chǎn)生的機理，由于摩托車的噪聲中發(fā)動機噪聲占很大比重，所以重點對發(fā)動機噪聲進行了闡述，包括機械噪聲、空氣動力噪聲、燃燒噪聲和表面輻射噪聲。隨后，本文介紹了噪聲源識別的幾種常用方法，并描述了各種方法的工作原理及其各自的適用范圍，重點闡述了聲強法。
結(jié)合本課題的內(nèi)容及現(xiàn)有條件，確定用近場聲強法作為此次實驗的測量方法，實驗是在發(fā)動機臺架上進行的，并把頻率分為低、中、高三個頻段分別進行分析，通過聲功率排序，最終確定了發(fā)動機氣缸、曲軸箱外殼、排氣管為主要噪聲源，并且確定聲源的頻率分布；隨后進行時間功率譜陣分析確定了在1000Hz左右發(fā)生共振，而這都為確定降噪措施提供依據(jù)。本文的最后還進行了一次驗證實驗，通過改進前后的實驗對比，確定降噪措施是否有效。


關(guān)鍵詞：摩托車噪聲，近場聲強測量，聲功率，時間功率譜陣













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 錄

中文摘要 Ⅰ
ABSTRACT Ⅱ
1緒論 1
1.1 引言 1
1.2 摩托車噪聲源識別的重要性及意義 1
1.3 國內(nèi)外研究現(xiàn)狀 1
1.4 本課題的研究內(nèi)容及目的 1
2 摩托車噪聲產(chǎn)生的機理 1
2.1 空氣動力噪聲 1
2.1.1 進氣噪聲 1
2.1.2 排氣噪聲 2
2.2 燃燒噪聲 3
2.3 機械噪聲 1
2.3.1 活塞對缸套的敲擊噪聲 1
2.3.2 配氣機構(gòu)噪聲 2
2.3.3 傳動齒輪噪聲 1
2.3.4 滾動軸承噪聲 2
2.4 發(fā)動機的表面噪聲 3
3 噪聲源識別的方法 1
3.1 聲強測量法 1
3.1.1 聲強測量法的理論依據(jù) 1
3.1.2 聲強測量原理框圖 2
3.1.3 聲強測量在主要噪聲源識別中的應(yīng)用 2
3.2 其他幾種方法 1
3.2.1 頻率分析法 1
3.2.2 分別運行法 2
3.2.3 鉛覆蓋法 1
3.2.4 表面振動速度（加速度）法 2
3.3 數(shù)字信號分析方法 3
4 摩托車噪聲源識別實驗及結(jié)果分析 1
4.1 實驗介紹 1
4.1.1 實驗裝置 1
4.1.2 測點布置 2
4.2 聲強測量結(jié)果及分析 1
4.2.1 前端面測量分析 1
4.2.2 左側(cè)面測量分析 2
4.2.3 右側(cè)面測量分析 1
4.2.4 頂面測量分析 2
4.2.5 消聲器右側(cè)面測量分析 2
4.2.6 總結(jié) 2
4.3 時間功率譜陣分析 3
4.3.1 梁平機場實驗測得 2
4.3.2 國檢中心實驗測得 2
5 改進前后實驗分析 1
5.1 實驗介紹 1
5.1.1 實驗裝置 1
5.1.2 測點布置 2
5.2 實驗數(shù)據(jù)及分析 1
5.2.1 改進前右側(cè)曲軸箱外殼表面的聲強測量分析 1
5.2.2改進后右側(cè)曲軸箱外殼表面的聲強測量分析 2
5.3 小結(jié) 3
5.4 實驗注意事項 3
6 結(jié)論 1
致謝 1
參考文獻