Compact Silencer Research Articles

Application of compact silencers as a noise barrier to a naturally ventilated double-skin façade

A prior study of the acoustical performance of a double-skin facade (DSF) as a noise barrier was carried out based on the percentage of the air vent open surface area, shading louver configurations, and shading louver surface materials. Earlier research findings led to experimental investigations of the acoustical performance capabilities of compact silencers to replace DSF air vents as both noise barriers and air channels because DSF air cavities, which contribute to natural ventilation performance (e.g., wind-driven or buoyancy-driven performance), are acoustically vulnerable to noise transmitted through the air vents. This experimental investigation aims to explore noise reduction (NR) through compact silencers applied to DSF air vents. Double-skin facade mock-up test cases were designed based on three test scenarios of a ventilation open surface area: (1) a 100%air vent open surface area (open mode), (2) a 0% air vent open surface area (closed mode), and (3) a compact silencer. From a data analysis of DSF mock-up test results, the overall NR values of a DSFmock-up ranged from20 to 37 dB(A) depending on the number of compact silencers and the shading louver orientation used. Configurations of compact silencers and shading louvers helped the DSF mock-up achieve additionalNR values of 5 to 10 dB(A) depending on the test case. Moreover, applying compact silencers to a naturally ventilated DSF mock-up led to significant noise reduction at low frequencies (125Hz).

Малогабаритні глушники для короткоствольної зброї

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.

The effects of horizontal shading device orientation and surface material and the use of a compact silencer in forming acoustical barriers for a ventilated glass double skin facade

Acoustical discomfort due to traffic noise transmission via operable windows is a significant environmental stress for building occupants in urban areas. A ventilated double skin facade, DSF, can potentially address the issue of noise transmission and operable windows. A hypothetically designed glass DSF mock-up was constructed in the opening between the reverberation rooms at the University of Kansas to determine the noise reduction of the DSF mock-up based on the orientation and surface materials of the horizontal shading devices and the use of a compact silencer in place of a typical ventilation grille in the outer skin opening. The compact silencer provides natural ventilation by allowing outside air to flow within the cavity of the DSF. For these laboratory tests, the horizontal shading devices with sound absorbing material were oriented at 0, 30, 60, and 90 degree angles. The laboratory noise reduction measurements are presented for the mock-up with the several shading device orientations and materials and for the use of a compact silencer.

A Compact Silencer for the Control of Compressor Noise

Current trends for IC-engines are driving the development of more efficient engines with higher specific power. This is true for both light and heavy duty vehicles and has led to an increased use o ...

Development of composite plate for compact silencer design

A compact flow-through plate silencer is constructed for low frequency noise control using new reinforced composite plates. The concept comes from the previous theoretical study [L. Huang, Journal of the Acoustical Society of America 119 (2006) 2628–2638] which concerns a clamped supported plate enclosed by rigid cavities. When the grazing incident sound wave comes and induces the plate into the vibration, it will radiate sound and reflect sound. Such sound reflection causes a desirable noise reduction from low to medium frequency with wide broadband. The structural property of the very light plate with high bending stiffness is very crucial element in such plate silencer. In this study, an approach to fabricate new reinforced composite panel with light weight and high flexibility to increase the bending stiffness is developed in order to realize the function of this plate silencer practically. The plate silencer can be constructed in more compact size compared with the previous two-plate silencer with two rectangular cavities and the performance with the stopband of the range from 229 to 618Hz, in which the transmission loss is higher than 10dB over the whole frequency band without flow or with flow at the speed of 15m/s, can be achieved. The experimental data also proves that the non-uniform clamped plates with thinner ends perform very well. To implement the use of such silencer practically in controlling noise at different dominant frequency ranges, a design chart has been established for searching the optimal bending stiffness and corresponding stopband at different geometries.

Numerical Assessment of Multi-Splitter Mufflers Using Neural Networks, the Boundary Element Method, and the Genetic Algorithm

Recently, research on new mufflers lined with sound-absorbing material has been addressed in the industrial field. On the basis of the transfer matrix method and the stiffness matrix method, most researchers have explored noise reduction effects. Yet, the maximum noise reduction of a compact silencer equipped with sound-absorbing splitters within a constrained space, which often occurs in modern industries, has been ignored. Therefore, the optimum design of mufflers becomes essential. In this paper, a one-chamber muffler equipped with multiple sound-absorbing panels within a fixed length is assessed. In order to facilitate the assessment of optimal mufflers having multiple sound-absorbing splitters, an approximated simplified objective function (OBJ) is established in advance by linking the boundary element model (BEM) with a polynomial neural network fitted with a series of real data, input design data (muffler dimensions) and output data obtained by BEM simulation. To assess the optimal mufflers, a genetic algorithm (GA) is applied. Before the GA operation can be carried out, the accuracy of the mathematical models must be checked using the experimental data. On the basis of the fixed total thickness of the splitters, the open area of the flowing channel can be assured. Therefore, not only the influence of the backpressure can be minimized, but also the cost of the sound absorbing splitters can be economically saved. Optimal results reveal that the maximum value of the sound transmission loss (STL) can be improved at the targeted frequencies. Consequently, the optimum algorithm proposed in this study provides an efficient way to find a better silencer for industry.

Reduction of Discrete‐Frequency Fan Noise Using Slitlike Expansion Chambers

As is generally known, discrete‐frequency noises are radiated from fans due to rotor‐stator interaction. Their fundamental frequency is the blade‐passage frequency, which is determined by the number of rotor blades and their rotating speeds. To reduce such noises, several types of silencers have been designed. Among them, the authors noted a slitlike expansion chamber (hereafter referred to as slit, for simplicity) and have studied its performance. A slit is a simple expansion chamber with a very short axial length that is placed in a duct. A slit with a circular cross‐section that is concentric with a circular duct may be studied using the same interpretation as is used for a side‐branch resonator muffler (closed‐end tube connected to a duct); that is, the resonant frequency of a slit depends on its depth (with an open‐end correction). It is expected, hence, that a slit might be applicable as a simple and axially compact silencer that is effective on discrete‐frequency noises. In this article, the properties of a slit are introduced, and the applicability of a slit to actual rotating machinery is described using experimental data.