공회전시 배기계 이음에 대한 수학적 계산 및 예측기법에 대한 연구

In general, the main source of vehicle noise is the ignition of engine and to diminish the degree of the noise, exhaust system is used as complicated filters for attenuating the noise more or less. But, even these kinds of filters are playing their roles at their expected frequencies bands, some noises still can be detected by passengers. They are so called ‘abnormal noises’ ,which are discovered when their anti-filters are working well, and it is very difficult to find what is the real problem and what is the basis of this phenomenon. Usually, frequency analysis is the most useful method for studying noise phenomena, but main effect of abnormal noise comes from listener’s feeling, therefore only frequency analysis process is not enough to clarify not only the cause but also the phenomenon itself. In this study, one of the abnormal noise, which can be detected very easily at the tail pipe, has been examined by mathematical way to define the cause of feeling of abnormal noise more effectively and precisely, furthermore also noise filter development process has been developed as a result in order to design proper filter system for exhaust system. For the validation of this calculation and design process, virtual noise has been exerted to calculated filters which had been designed properly by the calculation of former step and then, the noise has been accessed as a listener’s feeling by sound feeling matrices of octave band modulation.