SOUND-ABSORBING COMPLEX AS A MEANS OF REDUCING THE EXTERNAL NOISE OF THE ARMORED VEHICLE «BARS-8»

In order to reduce the level of external noise of the armored car “Bars-8” it is proposed to use a sound-absorbing complex (SAC). Attention is paid to that part of the external noise that is created under the bottom of the car. This noise is quite specific, because it creates not only the car but also the road surface. As a result of the interaction of the car with the road surface of different types there is noise, the spectrum of which is almost impossible to predict. Existing methods of reducing the external noise of cars can not be used to suppress this type of noise. The proposed SAC due to its design features has the ability to change its frequency response in unison with the change in the frequency response of the noise under the bottom of the car. SAC consists of several complexes of glass plates that have different sound-absorbing properties. This is necessary to change the frequency response of the SAC depending on the road surface and speed of the armored vehicle. A real-time noise spectrometer analyzer is used to adjust the frequency response of the SAC. A model of sound absorption of the bottom-road system using the sound absorption coefficient has been developed. For the first time when considering the external noise of the car, the concepts of room acoustics are used. The “bottom-road” system is considered in space in the form of a rectangular parallelepiped, the upper face of which is the bottom of the car, the lower – part of the road, which is a projection of the bottom. The reverberation time was calculated for this system without sound-absorbing complex and with the latter. As a result of the application of SAC installed on the bottom of the armored car, the external noise level of the “Bars-8” armored car is expected to be reduced by approximately 3 dBA in the speed range of 45–110 km/h. Keywords: armored car, “Bars-8”, camouflage, frequency, sound absorption coefficient, reverberation time, sound-absorbing complex, room acoustics, noise meter, noise meter-spectrum analyzer.