Method of calculation of probabilistic estimation of noise emitted by passenger automobile aggregates

The article deals with the problem of noise reduction of vehicles. Noise pollution is an important environmental problem. Currently, the level of urban traffic noise varies from 70 to 95 dBA, which significantly exceeds the current sanitary standards. The main source of vehicle noise is the engine and its systems. In the engine noise, the component caused by the combustion process and mechanical component are mentioned. The next most important source of noise are transmission units. In them, noise is generated by gears, bearings and fast rotating shafts. Tires of a moving vehicle are one of the main sources of vibration and noise at high speeds (from 80-90 km / h). Sources of noise of aerohydrodynamic origin are stationary or nonstationary processes in gases. One of the most intense aerodynamic sources of noise is vortex formation in flowing parts of mechanisms. When the vehicle is moving in the air stream, it is a source of turbulence, so noise increases with increasing speed. The authors carried out a number of experimental studies of the noise emission of individual units of a automobile - engine, gearbox, cardan gear, differential, exhaust system. Taking into account the results of experimental studies, a technique is proposed for the probabilistic calculation of the vehicle noise. A mathematical model is developed for calculating the expected noise in the passenger compartment of passenger automobiles, which allows obtaining not only the mathematical expectation of noise levels from each unit and its spectral components, but also their dispersion. On the basis of the model, a program has been created that makes it possible to obtain the spectral noise components from each of the sources in one-third octave bands with an estimate of the probable range of their values (confidence intervals) even at the design stage of the vehicle, which allows us, at the design stage, to lay down the necessary characteristics of the noise emission of aggregates and the automobile as a whole. The created technique can be successfully used also for an estimation of characteristics of noise emission of other vehicles - cargo and other automobiles, buses, wheeled and caterpillar tractors, agricultural machines.

noise level, experimental research, noise emission by automobile aggregates, probabilistic evaluation of automobile noise