Study Of Engine Acoustic Signals

One of the most fundamental and effective methods to reduce automobile noise is the control of radiated noise from engine surface. More and more automobile enterprises have attached important to research into the control of radiated noise from engine surface. This dissertation takes example for JL475Q engine and makes researches on analysis and control radiated noise from engine surface.Engineblock is the most important part of radiated noise. About forty-five percents of radiated noise from an entire engine are from the engineblock. So this paper makes an engineblock as research object, researches radiated noise from the engineblock surface, and takes some concrete measures against radiated noise from them.Aimed at the engineblock, this thesis directly researches its radiated noise field using FEM and BEM. Firstly, this paper does a model analysis for the suspended engineblock in ANSYS software, and then analyzes structural vibration for the engineblock using FEM, and after that computes sound intensity of radiated sound field from the engineblock using BEM in sound-vibration analysis software SYSNOISE and distinguishes sound source from radiated noise from the engineblock surface using sound intensity recognition method. It is found that the sound resources of the engineblock locate the water pump support,the upper end linking the clutch and the two sides. The end linking the timing gears cap, the side wall of cylinder and the skirt section of the engineblock are the sound radiation resources of the two engineblock sides. Except that, this thesis calculates sound power level of radiated noise from the engineblock with MATV method. It is found that the noise radiated from the engineblock is slightly loud. The sound power level is up to 108.84 decibels. The noise radiated from the engineblock at 850Hz is the loudest. After that, a measure that controls radiated noise from the engineblock surface is taken in this paper. At last, it is known that the sound power level reduces to 100.35 decibels from 108.84 decibels, and the measure has a definite effect on noise reduction.The control measures to reduce radiated noise from engine surface that are brought out in this dissertation have some effects. And all of these measures are very economic and feasible. The research methods in this paper have some reference value to research radiated noise field of vibrated objects using computer analysis technology.