6HHE-VE-6型压缩机辐射噪声试验分析

根据国家标准GB/T4980-2003，采用简易法对6HHE-VE-6型压缩机辐射噪声声功率级和噪声频谱图进行了测量，分析了其噪声频谱分布规律。     

关于变电站噪声评估模拟及防治措施研究

本研究以国网某1000kV变电站作为案例,进行变电站噪声源的辨识,确定变电站噪声源的发生原理,并制定了控制措施.首先确定分析用的主要噪声源及其声功率级、频谱特性、声源高度等特性.然后基于《环境影响评价报告书》的要求,确定了噪声控制设计标准.最后根据噪声发声体的声功率级,利用SoundPLAN软件对站内外不同位置进行噪声...     

DH63型离心压缩机辐射噪声实验研究

根据国家标准GB—2 888,采用邻近声场法 ,利用声级计、盒式磁带记录仪和频率分析仪对DH63型离心压缩机辐射噪声声功率级和噪声频谱图进行了测量 ,分析了该型压缩机的噪声频谱分布规律     

DHP40-4型离心压缩机辐射噪声试验研究

采用邻近声场法,按照国家标准ＧＢ／Ｔ２８８８,对ＤＨＰ４０－４型离心式压缩机辐射噪声声功率级和噪声频谱图进行了测量,分析了其噪声频谱分布规律,试验得到：ＤＨＰ４０－４离心式压缩机噪声的主要频带范围在５００～８０００Ｈｚ内,噪声最大值在２０００Ｈｚ左右。     

维纳滤波器在燃烧噪声分离中的应用

目前分离内燃机燃烧噪声常用的方法主要有传递函数法、多元线性回归法,这两种方法均将内燃机的总噪声分为燃烧噪声和机械噪声两部分,并且假设实验获得的倒拖噪声为机械噪声,以此达到分离燃烧噪声的目的。然而上述两种方法所得到的燃烧噪声中还包含活塞敲击所形成的间接燃烧噪声。本研究测取了某汽油机转速为4 500 r/min和2 000 r/min转速下多个负荷工况的总噪声、缸压和振动数据,并利用-15～85℃A ATDC的时间窗对测量信号进行了截取,基于倒拖法将机械噪声分离。利用缸压信号和燃烧噪声信号构建了维纳滤波器对燃烧噪声进行了滤波,实现了直接燃烧噪声和间接燃烧噪声的分离。计算结果表明该汽油机活塞敲击产生的间接燃烧噪声主要集中于500～8 000 Hz的频率段。     

内燃机噪声的形成原因及减小措施

通过柴油机气流噪声、机械噪声和燃烧噪声的各自形成原因的研究，依据噪声产生的部位及其产生的机理，结合生产实践，利用频谱分析，指出减小柴油机3种噪声应分别采取的措施。     

挖掘机噪声测试分析与降噪措施

随着挖掘机行业的发展,挖掘机应用越来越广泛,用户对挖掘机性能与舒适性的要求不断提高。为满足更高的舒适性要求,对某型挖掘机的整机声功率级和噪声频谱进行测试与分析,明确整机噪声的主要来源。针对挖掘机噪声的主要来源提出降噪措施,并进行效果验证,达到降噪目的。     

柴油机噪声源识别与噪声特性研究

以某型号柴油机为研究对象,测量了柴油机外特性工况、负荷特性工况下的整机噪声和主要零部件近场噪声,结合频谱分析进行了噪声源识别。研究结果表明,柴油机标定工况的整机声功率级106.3 dB(A);在负荷不变的情况下,柴油机噪声随着转速的上升而增大。高转速时,柴油机负荷的变化对噪声影响不大;柴油机近场噪声较高的部位是油泵、油底壳、曲轴皮带轮和空气滤清器;低速时,进气噪声是柴油机主要噪声源,频率120~125)Hz处的峰值与周期性压力脉动频率相吻合,频率315 Hz处的峰值与气柱共振系统的固有频率相吻合,气柱共振噪声要高于周期性压力脉动噪声。     

便携式多功能噪声特性测试分析仪

设计了一种基于虚拟仪器的便携式多功能噪声特性测试分析仪.详细介绍了该仪器的硬件组成、软件结构、声级计与声功率计等功能模块设计流程,最后给出系统实现.该仪器以LabVIEW为软件平台,采用USB9233为噪声数据采集卡,集普通声级计功能与压缩机标准噪声声功率级测试功能于一体,具有体积小、不需电源、精度高、快速给出评价结果的优点.该仪器还可应用于工业过程中需要噪声声压级或声功率级测量的众多场合.     

低压轴流风机设计参数对紊流噪声的影响

基于Lee的模型编写了紊流噪声预估程序,并将其引入到低压轴流风机设计程序中。同时与Fukano噪声模型进行了对比。预估程序最终输出噪声的总声功率级和总声压级。进一步研究了风机不同设计参数对噪声的影响,如变环量指数、轮毂比等。分析表明,风机流道内的相对速度对噪声的影响较大,弦长在噪声影响因素中处于次要地位。     

中、小型内燃机电站噪声频谱试验研究及降噪措施

通过试验研究确定内燃机电站噪声频谱,找出主要的噪声来源,采取相应降噪措施,有效的降低了内燃机电站的噪声。     

Psychoacoustic study on contribution of fan noise to engine noise

There are more researches on engine fan noise control focusing on reducing fan noise level through optimizing fan structure,and a lot of research achievements have been obtained.However,researches on the effect of fan noise to engine noise quality are lacking.The influences of the effects of fan structure optimization on the engine noise quality are unclear.Thus,there will be a decline in fan noise level,but the deterioration of engine noise quality.Aiming at the above problems,in consideration of fan structure design and engine noise quality,an innovative method to analyze the contribution of fan noise to engine noise quality using psychoacoustic theory is proposed.The noises of diesel engine installing different cooling fans are measured by using the acoustic pressure method.The experiment results are regarded as analysis samples.The model of sensory pleasantness is used to analyze the sound quality of a diesel engine with different cooling fans.Results show that after installing 10-blade fan in medium diameter the sensory pleasantness at each test point is increased,and the increase is 13.53% on average,which indicate the improvement of the engine noise quality.In order to verify the psychoacoustical analysis,the subjective assessment is carried out.The test result shows the noise quality of engine installed10-blade fan in medium diameter is most superior.1/3 octave frequency spectrum analysis is used to study the reason of the improvement of engine noise quality.It is found that after installing proper cooling fan the sound pressure level below 400 Hz are obviously increased,the frequency assignment and spectral envelope are more reasonable and a proper cooling fan can optimize the spectrum structure of the engine noise.The psychoacoustic study is applied in the contribution of fan noise to engine noise,and the idea of engine sound quality improvement through the structure optimization is proposed.     

Separation of combustion noise and piston-slap in diesel engine—Part I: Separation of combustion noise and piston-slap in diesel engine by cyclic Wiener filtering

The main purpose of this study is to characterize the relative noise given out by a diesel engine, around the Top Dead Centre (TDC) by quantifying the proportions of “mechanical noise” originating mainly from piston-slap on the one hand and ‘thermal noise” originating from combustion on the other hand. Two different approaches are described here to solve this problem.In the first part of the paper, the cylinder pressure is measured and used as a reference in order to reconstruct the thermal noise. Next, we propose a method based on applying a cyclic Wiener filter to the measured cylinder pressure in order to separate the noises of mechanical and thermal origins. The final result is to reduce the engine resulting noise.The second part of the paper is devoted to blind source separation (BSS) methods applied on signals issued from accelerometers placed on one of the cylinders. It develops a BSS method based on a convolutive model of non-stationary mixtures and introduces a new method based on the joint diagonalization of time varying spectral matrices of the observations. Both methods are then applied to real data and the estimated sources are finally validated by several physical arguments.     

内燃机机械噪声的声强测量和识别技术及其控制方法

阐述了声强测量和识别技术的基本原理和发展现状,并具体说明声强技术在噪声测量和识别中的应用.讨论了如何在识别噪声源之后对内燃机机械噪声进行控制.     

Diesel engine combustion and mechanical noise separation using an improved spectrofilter

The present paper is dedicated to diesel engine combustion and mechanical noise separation. It is shown that this separation can be performed by a spectrofilter if and only if the spectrofilter is computed using only the random part of the engine signals. This source separation is a difficult task, since the sources are correlated and overlapped both in time and frequency domains. Considering only the random part of the signals virtually uncorrelates the noise sources, making them easier to separate. This approach is validated by the results of a simulation. An experiment based on real engine signals shows that the spectrofilter is more causal and more robust if computed using only the signals random part. This experiment also shows that speed rotation and load condition affect the engine transfer functions.     

Identification of complex diesel engine noise sources based on coherent power spectrum analysis

This paper presents an identification of complex diesel engine noise sources based on coherent power spectrum analysis. Noise sources identification is essential for making noise reduction strategies. The author adopts methods of hierarchy diagnosis together with coherent power spectrum analysis to identify complex noise sources of diesel engine. In investigation of the noise sources, the hierarchy tree and judgment matrix are given. Through noise sources identification, the main part of radiating surface noise is found. The result shows that the noise of low-frequency belt is mainly machinery noise from oil pump, gear and valve mechanism, etc., and it is radiated mostly from thin-walled part like gear cover and valve cover etc., while the noise of high-frequency belt is mainly combustion noise and oil pan is identified as the main part of noise reduction.     

V型双缸柴油机噪声源及其激励源响应的识别分析

采用基于四阶累积量的JWSmICA技术,对V型双缸柴油机噪声源及其激励源进行识别。该技术首先在不同工况下利用单缸熄火法对机械噪声和燃烧噪声进行了分离与识别,得到了柴油机主要噪声源,然后把基于四阶累积量的联合近似对角化算法(JADE)及小波时频分析结合起来,对标定工况下噪声源的主要激励源响应进行了分离与识别,结合单缸熄火与ICA识别结果,找到了以气门落座冲击和活塞敲击为主的主要机械激励源与燃烧激励源。利用该技术分析得出了降低燃烧激励源响应的中低频振动能量是控制噪声源关键的结论。     

脉冲爆震发动机模型机噪声辐射特性初探

对脉冲爆震发动机模型机在不同爆震频率下的噪声辐射特性进行研究。通过试验测量和数据处理，发现其噪声辐射呈现间歇性和周期性的特点，主要由单极子源和四极子源组成；噪声辐射的频谱为宽频带谱，其能量主要集中在低频部分（0～5000Hz），由气流脉动的基频（即爆震频率）和谐频组成；峰值声压级与爆震频率无关，脉冲声压级、声功率级、声功率随爆震频率的提高而提高。     

往复压缩机噪声诊断及降噪研究

对全封闭往复压缩机进行了声功率、声压级、壳体振动和壳体模态试验，分析了压缩机主要振动和噪声源．确定了壳体的振动模态，指出了进一步降低压缩机噪声的途径。确定2500Hz和3150Hz的峰值噪声主要是壳体的辐射噪声，并且采取了两种降噪措施，经试验比较，降噪效果明显。     

内燃机噪声源识别与噪声控制技术研究

内燃机工作时产生强烈的噪声,无论其应用于何种场合,降噪都是一个很重要的问题.本文着重剖析了用于内燃机噪声源识别的各种方法,并分别从燃烧噪声、机械噪声、进排气噪声和风扇噪声等方面进行了分析并提出了具体的解决措施.