Calculation of the required noise reduction of a engine exhaust system

The problem of reduction of internal combustion engine (ICE) noise is most urgent at present when the fleet of vehicles has significantly expanded and their power has increased. Reactive mufflers are often used to solve it. The initial stage in the design of mufflers is a theoretical assessment of the frequency spectrum of sound power level (SPL) of an unmuffled ICE noise source, comparing it with the calculated maximum permissible spectrum and determining the required amount of its reduction in standard frequency bands. The paper presents a method for calculating the required noise reduction of a transport engine exhaust using the example of a two-stroke ICE of the class of 125 cm3. Thus, the designer has the opportunity to develop mufflers, the acoustic efficiency of which meets the calculated required noise reduction values, already at an early stage of the vehicle design