Experimental Research on Noise Reduction of Mini-car

By means of noise sources separation experiment of mini car and the surface acoustic intensity measurement of the engine, this paper finds that the main noise source of the mini car is the intake noise. According to the frequency spectrum analysis of the intake noise, the design frequency of the three cavity Helmholz intake silencer is determined. The results of the experiments show that the silencer, which is patented, has a remarkable effect, about 8 dB(A) decrement, on the noise reduction of the mini car.     

Vibration & Noise Analysis on Double-ring Gear Reducer

Double-ring gear reducer with Central inputting shaft is studied. The basic structure of reducer as well as testing equipment, probe spot and testing method of Structure-borne noise and air-borne noise is presented. Based on frequency spectrum of each point, amplitude spectrum of structure-borne noise and testing results of air-borne noise, the authors analyze the vibration characters and latent faults of double-ring gear reducer, coming to the value and the cause of the noise, providing theoretical basis for proper design of the double-ring gear reducer and method of reducing its vibration and noise.     

Research on Bridge Structure Noise of Railroads and Underground

This paper analyses the generating mechanism of radiation noise which produced by bridge structures and vibro-acoustic characteristics, and reviews the current situation of the researches on the relevant standards of structure noise at house and abroad. The author summarizes the method of measurement and calculation about structural noise at house and abroad, further notes their limits. This paper explores the impact of such factors as rain speed and other different fluids on structure noise. The noise characteristics of structures like cavity structure and thin-slab structure are also discussed. Strategies for reduce the bridge structure noise are summed up by reducing the vibration of track structure, altering the structure of boundary conditions, increasing the stiffness and changing the bridge cross section. Finally it comes to a conclusion that a combination of these strategies is the root way to settle the question of the bridge structure noise.     

Identification of Minibus''s Surface Noise Source

With the study of minbus's accelerated exterior noise control,the principle of sound intensity measurement was applied,the sound intensity of a minbus's surface noise was tested,and the surface noise distribution was presented.Several identification of noise source methods including sound power,sound intensity contour map,frequency spectrum were used together for surface noise analysis and study.Engine radiation noise and exhaust noise was identified as the major noise sources.On the contrary,car body vibration noise,tyre noise,transmission agent noise,air admission noise just occupied a little proportion of surface sound radiation energy.The research provides the reliable basis to determine main projects of minibus's accelerated exterior noise control.     

Test Method of Indoor Noise for Micro-surfacing Mix

Micro-surfacing mix has been wildly used in the pavement maintenance for its water proofing, anti-skidding and wear resistance. However, micro-surfacing pavement has higher noise than the common asphalt pavement and its noise can not be measured effectively and accurately. Therefore, the indoor noise test method of micro-surfacing mix based on wet track abrasion test was explored. The micro-surfacing mix specimens were used to imitate the micro-surfacing pavement. The wet track abrasion tester was used to provide the vehicle loads. The sound level meter was used to measure the noise between tire and pavement. Furthermore, the indoor noise of nine kinds of micro-surfacing mixes with different gradation was examined. The results show that the equivalent sound level in the second time period has good relationship with the surface texture depth by sad patch method. Then the test method and test procedure for the indoor noise of micro-surfacing mix based on wet track abrasion test were given. Finally, two micro-surfacing mixtures with different gradations were made to validate the test method. The results show that the evaluation method can effectively distinguish the difference of micro-surfacing mixes with different gradation and can supplement the mix design method of micro-surfacing mixes.     

Accelerated Vehicle Exterior Noise Control of Minicar SC6360B

This paper studyies the method of controlling SC6360B's accelerated vehicle Exterior noise. First, the main noise is found, which is from engine compartment and from exhaust noise by the identification of vehicle noise resource. Second, this paper carris out the farther noise identification experiment on engine and the insert-loss experiment on the exhaust gas muffler. In the end, the authors make sure that the noise is mainly infected by direct leaked noise from engine compartment, radiation-noise caused by the vibration of engine accessories and loud exhaust noise because the muffler has dficient elimination . The corresponding methods has been adopted according to the analysis. Through the test, the noise is lowered 2.5 dBA than it was and reach the new requirement.     

Analysis and Countermeasures of the Power Noise During High Frequency PCB Design

The paper analyses many forms of power supply noise interference in the high frequency PCB and the relevant reasons. Combining several formulas with the relevant engineering experience, the authors bring forward a lot of related means; finally conclude the chief principle that controlling power noise should abide by.     

Wavelet-Based Multiresolution Analysis to Noise Elimination

The wavelet transform is a new subject developed quickly in the past ten years Compared with Fourier transform and Gabor transform, the wavelet transform is a part of time-frequency transform, so the message can be obtained from the signals effectively. By means of the fractionized multiresolution analysis to the signals, many problems unalbe to be solved by Fourier tranform have been solved in this way.Based on the fact that the maxima of the noise wavelet transform reduces dramatically with the increase of the scale, we obtain the result that this way is more advanced than the Fourier transform multiresolution analysis to the noise elimination.     

Speedy Recognition of Noise in Real Time Signal Based on Wavelet Transform

It's necessary to process position and gesture of rocket on real time within the flight of rocket. This work should base exact data. But much noise has been found in the data and the noise recognize is regarded as a focus. A speedy online arithmetic recognizing noise is proposed based on wavelet transform. The computing complexity measured by time of this arithmetic is a constant which is greatly reduces the works of calculation of wavelet transform. It can recognize the noise fast when the signal is gathered. The applications in these problems show that the effective arithmetic satisfies the needs of real time and can handle the real time data measured in other yields.     

Study on Surface Noise Distribution of Three ring Reducer

The three ring reducer is a kind of gear drive developed in the past decade. Adopting the new conception of "parallel and movable axis" of multiple mechanisms, this kind of gear drive has many characteristics such as large transmission ratio, high efficiency and so on. As the three ring reducer has been invented only for ten years, up to date the design of the gear drive is only made with analogue method, no design theory can be followed, there exist serious vibration and noise in transmission, which limit its wide application in industry. In this paper, the transmission principle of SHQ50 reducer is studied, the surface noise distribution of the reducer, transmission ratio 49.5 , is measured and analyzed by means of sound intensity method. The 3D distribution maps of noise on top of reducer, input side and output side of reducer, and left side and right side of reducer are drawn. With the sound intensity frequency maps of each measuring point, the sources of giving out noise are analyzed. The reducer of low vibration and noise can be designed rightly according to the analysis.     

Extensive Noise Control Model for Plastic & Rubber Sulfuration and Simulation

For the problem of precision and real time control in the process of sulfuration,a new control model is put forward.All the noise existing in the sulfuration process are unified as one kind noise named as extensive noise,and the control system is self-adaptive in the process.The purpose of this strategy is to solve the problem preferred.The model comprises of two parts: one is Neutral Networks which deals with the advance sort,the other is dynamic self-adaptive system which is used to find the system's factors.The simulation result of dynamic self-adaptive system shows that this extensive noise controlled model is valid in the process.     

Identifying Research on Noise Sources of Rotary Vane Compressor

This paper describes the noise mechanism of rotary vane compressor JSS -96 by the method of running independently, spectrum and the measurement of the sound intensity. The noise sources of this type compressor mainly include noise of electromotor, outlet noise and intake noise. Electromotor noise and outlet noise among them have most influence on the compressor noise. This is the further basis of noise control for rotary vane compressor.     

Abnormal Noise Test Method of Vehicle Hydraulic Shock Absorber

The work principle and abnormal noise test method of hind vehicle hydraulic shock absorber are analyzed, Based on experiment data and signal character analyse ,a test method is found to distinguish the abnormal noise of rear hydraulic shock absorber. Practical validates that the reliability rate of this test method can be over 98 percents, and it can be satisfied with the request of the factory. At last, the reason of abnormal noise is analyzed and simulated, the reason of different signal attenuation is explained, and the research conclusion is educed.     

Analysis on Valve Train Noise of Engine

To research the mechanical and influence factors of noise of valve train of engine, noise-distinguishing test is taken with one certain 125 mL engine valve train. The result reveals that the valve train noise mainly results from impacting between rocker and valve stick, impacting of valve seating. With the way of model set up and simulating calculation of kinematics and dynamic of valve train, the influence factor of rocker impact force and valve seating acceleration of valve train is studied, which reveals that the acceleration of valve and impacting force between rocker and valve stick are mainly relied on cam buffer segment lift, cam buffer segment wrap angle and coefficient of accelerating segment of cam buffer segment. Choosing these parameters reasonably is helpful to decrease the acceleration of valve and impacting force between rocker and valve stick, and then reduce the noise of valve train.     

Development of Automobile Noise and Vibration Analysing System with Object Otiented Technology

With the developing of the automobile industry, how to control the noise and vibration level of the products come to urgently for the auto factories during their developing and producing period. Finding out the main noise source and vibration source quickly, analyzing the noise and vibration signal effectively, contriving a noise descending algorithm reasonable and economical become the first and most important job for auto corporations. At the mean time it complicate the developing guide line of the noise and vibration testing system. With object oriented technology, we can develop the noise and vibration testing system in a short time and with a low cost. The object oriented technology emphasizes the circulation, exoteric and expandable of the codes. It enables us developing the system follow a flexible, integrable and economical procedure..     

Application of Sound Intensity Measurement Method in Spotting the Noise Source of Engine Surface

During the study of noise emitted by accelerating mini-vehicle control, using theory of sound intensity measurement, it is actualized spotting the noise sources with the mini-vehicle engine. In the procees of the contour of sound intensity and frequency spectrum analysis, main noises of the engine are from oil sump tank and delivery menifold shield and two-way branch exhaust pipe shield. These noises are produced from the engine combustion. According to all analysis, the authors bring forward methods of modifying structure of shield-shell parts and consider them as main methods of reducing noises.     

Experiment Analysis on Noise of the Minibus Exhaust Muffler

On the basis of analysis and research on an automobile exhaust noise, the theory and test combination method was adopted to improve the muffler, and then the acoustics performance of muffler was validated by doing some experiments with the engine. On different speeds of the engine, the inserting loss and spectrum characteristic under several muffler methods were studied. Finally the best muffler method was confirmed, and the purpose of reserving was achieved.     

Application of Sound Intensity Technique to Measure the Noise of Electromotor

This paper has explained the characteristics,virtue of sound intensity measurement and the principle. And compare with traditional sound pressure measurement. The principle and composing of virtual sound intensity measurement system based on two-channel FFT analysis are researched. The sound power of large turbogeneratorin operating site is determined by means of sound intensity measurement and sound pressuremeasurement. Itis demonstrated that the method of sound intensity measurement of engine is practicable and the measuring data are valid and the method conquers the problems of traditional method of sound pressure measurement which is apt to environmentinfluence and sound power measurement need to especially acoustic environment. It is proved that the sound intensity method is especially suited to determine highaccuratelythe sound Power level of the electrical machines operating in situated conditions especially in case of acoustically worst environments or on loadand themethod is so superiorityin noise measurement.     

A Practical Method of Eliminating the White Noise of Partial Discharge with Wavelet

The white noise of PD(partial discharge) signal brings great difficult to the PD signal's processing, so eliminating the white noise is a necessary section. There are many methods of eliminating white noise, but none of them are suitable to the PD signal processing. Because PD signal and white noise have different Lipschitz exponents and different wavelet transform features in time-scales, a new eliminating white noise method has been brought forward that has simple operation and meets the timing need of PD signal's processing. After the processing with this method, the PD signal is not distortion and the effect of eliminating white noise is very good. This method can be applied to the processing of PD signal gotten from the site.     

Analysis of Elevated Structure Radiated Noise with BEM-FEM Method

Urban rail transit is becoming an important means of transportation and elevated structure is one important part of urban rail transit. So the radiation noise induced by elevated structure attracts more and more attention. Based on the theory of Helmholtz integral equation of BEM and fluid-structure coupling system of FEM, the sound pressure transmission vector reflecting the relation between structural vibration acceleration and radiation of sound pressure is derived and solved by the element radiation superposition method. The calculated results are in good agreement with the experimental data from a viaduct section of the Beijing airport rapid rail transit.