© Volodymyr Fedorov, Candidate of Technical Sciences (Ph.D.), Associate Professor of the Department of Motor Vehicles, e-mail: firstname.lastname@example.org, ORСID: 0000-0002-1085-5112 © Halyna Filipova, Candidate of Technical Sciences (Ph.D.), Associate Professor, Professor of the Department of Motor Vehicles, e-mail: email@example.com, ORCID: 0000-0003-3427-7633 © Vasyl Yanovsky, Candidate of Technical Sciences (Ph.D.), Associate Professor of the Department of Motor Vehicles, e-mail: Yanovskyi_v@ukr.net, ORCID: 0000-0001-9437-4537 © Oleksandr Ternovyy, Master Degree, e-mail: firstname.lastname@example.org (National Transport University) REDUCTION OF EXTERNAL NOISE VEHICLE of SPAI “BOHDANA” ON THE BASIS OF THE KrAZ-63221 IMPROVED TWO-CHAMBER REACTIVE NOISE SILENCER Abstract. High-quality military equipment is a vital necessity for the independent state of Ukraine, especially in the conditions of aggravation of the situation at the front. One of the parameters that determines the quality of military vehicles is the level of external noise. The external noise of this type of car, in addition to the negative impact on human health (including the crew), is also an unmasking factor. In order to reduce the level of external noise of SPAI “Bogdan” on the basis of the chassis KrAZ-63221, the use of an advanced two-chamber jet muffler of the exhaust gases of the internal combustion engine is proposed. The known two-chamber jet muffler of exhaust gases has a fixed internal partition. Its acoustic efficiency is described by a known formula. It is proposed to make the inner partition of the muffler movable. This need arises from the fact of constant changes in the speed of the engine crankshaft during the movement of the car. The change in the position of the inner partition is consistent with the change in the speed of the crankshaft, because these two processes are synchronized. The mathematical package IDL was used to analyze the known formula for the efficiency of a two-chamber jet exhaust muffler of an engine with a movable inner partition. Given the need to show the dependence of the efficiency of the muffler simultaneously on two parameters – the speed of the crankshaft and the position of the movable inner partition of the muffler – the method of color coding was chosen. The design of a two-chamber jet noise muffler developed for ACS “Bogdan” is given. As a result of introduction of the developed muffler noise reduction of level of external noise of the SPAI “Bogdan” on the basis of the chassis KrAZ-63221 car on 2–3,5 dBA in the range of speeds of movement of 45–85 km/h is forecasted. Keywords: automobile, SPAI, KrAZ, masking, internal combustion engine, jet muffler, acoustic efficiency, frequency, color coding method, speed. References 1. Fedorov, V. V., Yanovsky, V. V., Kovalshuk, D. M. (2019) Vdoskonalenyy hlushnyk shumu broneavtomobilya KrAZ «Fiona» [An improved armored vehicle KrAZ «Fiona» noise silencer]. Kyiv, Avtoshlyahovik Ukraine, 1 (257), 20–25. 2. SPAI «Bogdan» KrAZ-63221. Specifications (2019) Retrieved from http://www.autokraz.com.ua/index.php/uk/produktsiya/automobile/military/spec/item/4147-samokhidna-artyleriiska-ustanovka-bohdana-kraz-63221. 3. Alekseev S. P., Kazakov A. M., Kolotilov N. N. (1970) Bor’ba s shumom i vibratsiyey v mashinostroyenii [Fighting noise and vibration in mechanical engineering]. Moscow, Mashinostroyeniye, 208. 4. https://www.l3harrisgeospatial.com/Software-Technology/IDL. 5. Razumovsky M. A. (1981) Prognozirovaniye shumovykh kharakteristik porshnevykh dvigateley [Prediction of noise characteristics of piston engines] Minsk, Vysheyshaya shkola, 31.