Browse Publications Technical Papers 2011-26-0065
2011-01-19

Prediction of Muffler Radiated Noise for a Diesel Engine 2011-26-0065

Exhaust noise is the major noise source for the automotive vehicle contributing to its interior as well as exterior noise. The Transmission Loss (TL), noise reduction, Insertion Loss (IL) and radiated noise are the major characteristics used to describe the performance of a muffler in an automotive exhaust system. Out of these characteristics, Insertion loss and exhaust radiated sound pressure levels plays a significant role in muffler design as it is a measure of true performance of muffler along with engine/vehicle and very much useful for the designers to compare different silencer configurations. In present work, the sound source is modelled by acoustic impedance and volume velocity of the engine. Since it is difficult to estimate the sound source impedance of the exhaust by measurements either with direct or indirect methods as both are prone to errors and difficult to implement, the empirical equations are used to define exhaust source, to have reasonable accuracy. In present study, the sound pressure at the exhaust opening is measured for different acoustic loads. The volume velocity is calculated backwards using the above measurement result and the numerical model of acoustic loads used. Estimation of Sound Pressure Level (SPL) at the exhaust opening has become possible by using source acoustic impedance and volume velocity, as the boundary conditions of the exhaust system model. Comparison of predicted and measured SPL is also presented for different engine speeds under full load condition.

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