RESEARCH OF ACOUSTIC PROPERTIES ELLIPTICAL (SPHERICAL) MUFFLER

In this work, spherical and hemispherical silencers of exhaust gases of internal combustion engines are consid-ered as separate cases of an elliptical silencer. Spherical and hemispherical mufflers are preferred over elliptical mufflers based on their cheapness and ease of implementation with practically the same acoustic efficiency. The schemes of operation of both of the above silencers were considered: the movement of exhaust gases in them, incoming and reflected sound waves. Assembly drawings of a hemispherical muffler as a special case of an elliptical muffler were also given. An-alytical studies of the acoustic properties of the developed elliptical noise muffler in the low frequency range were carried out. In the high- and medium-frequency frequency ranges, the elliptical muffler suppresses noise due to the effect of sound reflection from the walls of the muffler and returning the latter back to the exhaust pipe. For low-frequency noise, such an effect is practically absent. This type of noise is suppressed in the developed muffler due to the high sound-absorbing properties of the muffler’s inner walls. To determine the effect of noise suppression in the low-frequency range, the laws of architectural acoustics were used, in particular, the reverberation time was calculated for geometric mean frequencies from 125 Hz to 6000 Hz. To ensure high sound-absorbing properties of the internal surfaces of the muf-flers, the use of special glass is proposed. The approximate dependence of the sound absorption coefficient of special glass on frequency is given. In the process of calculating the acoustic efficiency of the muffler, the dependence of the re-verberation time in the muffler on the noise frequency was obtained. At the same time, it was established that the effi-ciency in the area of low frequencies is 30 dB. Keywords: armored car, “Novator”, noise muffler, exhaust gases, acoustics, elliptical muffler, spherical muffler, sound absorption, glass, frequency, acoustic efficiency.