Small-size silencers for stub-barreled arms

This paper describes the designs and manufacturing and testing features of small-size silencers developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine for arms used in enclosed space. The topicality of the development is due to the use of stub-barreled arms by Ukrainian special subunits. With consideration for the features of existing silencers for submachine guns of special subunits, a line of compact silencer development was chosen. The paper formulates requirements for the design of silencers for stub-barreled small arms and material and manufacturing accuracy requirements for their components. The use of silent stub-barreled small arms in enclosed space without damaging the shooter’s organs of hearing is justified. In combat operations, sound suppression allows subunits to contact with one another and their commanders to have the situation under control. The paper shows the features of design solutions and describes the design of the silencers’ internal components and their effect on the operating efficiency for different embodiments of theirs. The paper presents the appearances, construction arrangements, and specifications of the small-size silencers developed and the results of their full-scale tests. The sound suppression efficiency of the silencers developed was measured with a sound level meter and verified by comparison tests with basic prototypes developed earlier. The efficiency proved to be (28 – 34) dBA, which is on a level with their best foreign counterparts. The test showed that: - the silencers do not affect firearm automatics and sustain standard firing regimes, - the silencers do not affect the shot grouping characteristics, and - the silencers do not affect other performance characteristics either. Hence the compact silencers developed for stub-barreled submachine guns (assault rifles) are efficient and reliable.

DEVELOPMENT AND APPL.ICATION OF A PORTABLE LIGHTWEIGHT SOUND SUPRESSION PANEL TO REDUCE NOISE AT PERMANENT AND TEMPORARY WORKPLACES IN THE MANUFACTURING AND REPAIR WORKSHOPS

This research falls in the field of machine-building, construction and woodworking, concerns sound suppression panels for cabins, enclosures, soundproofing acoustic shields, temporary room partitions, etc., and solves the problem of making sound suppression panels easy for installation and dismantling, as well as transportable and storable, without reduction in noise suppression effectiveness. For thispurpose, pads connected with two parallel sheets are placed between them. The pads form a layer which cross section is a chain of rhombuses, and the parallel sheets have curvature lineson the level of the rhombuses connection. The portable lightweight sound suppression panel (SSP)with a diamond-shaped structure is made of organic and polymer materials, such as pulp-and-paper materials, fabrics and polymer films which can significantly reduce the structure weight.

Locally Resonant Phononic Crystals at Low frequencies Based on Porous SiC Multilayer

In this work, a one-dimensional porous silicon carbide phononic crystal (1D-PSiC PnC) sandwiched between two rubber layers is introduced to obtain low frequency band gaps for the audible frequencies. The novelty of the proposed multilayer 1D-PnCs arises from the coupling between the soft rubber, unique mechanical properties of porous SiC materials and the local resonance phenomenon. The proposed structure could be considered as a 1D acoustic Metamaterial with a size smaller than the relevant 1D-PnC structures for the same frequencies. To the best of our knowledge, it is the first time to use PSiC materials in a 1D PnC structure for the problem of low frequency phononic band gaps. Also, the porosities and thicknesses of the PSiC layers were chosen to obtain the fundamental band gaps within the bandwidth of the acoustic transducers and sound suppression devices. The transmission spectrum of acoustic waves is calculated by using the transfer matrix method (TMM). The results revealed that surprising low band gaps appeared in the transmission spectra of the 1D-PSiC PnC at the audible range, which are lower than the expected ones by Bragg’s scattering theory. The frequency at the center of the first band gap was at the value 7957 Hz, which is 118 times smaller than the relevant frequency of other 1D structures with the same thickness. A comparison between the phononic band gaps of binary and ternary 1D-PSiC PnC structures sandwiched between two rubber layers at the micro-scale was performed and discussed. Also, the band gap frequency is controlled by varying the layers porosity, number and the thickness of each layer. The simulated results are promising in many applications such as low frequency band gaps, sound suppression devices, switches and filters.