• Title, Summary, Keyword: Acoustic Absorber

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Optimum Design of High Voltage Fuse Holder with a Built-in Acoustic Absorber System (흡음장치를 내장한 고전압 퓨즈홀더의 최적설계에 관한 연구)

  • Jin, Yeung-Jun;Lee, Hae-Won;Hwang, Yu-Sub
    • Journal of the Korean Society of Safety
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    • v.26 no.1
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    • pp.8-14
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    • 2011
  • Noise and vibration are likely to disturb the sensory system of human body leading to psychological stress and thereby property damage. In this research, a cut out switch(COS) with a built-in acoustic absorber along with a COS fuse broken was developed to reduce percussion noise. This new system is based on a design approach that combines existing absorber systems: expansion type, resonator type, and acoustic absorber type silencer The noise performance of the new system was simulated using the $SYSNOISE^{TM}$ software under optimized parameters: the diameter of perforated plate 2 mm, the plate thickness 3 mm, the width of expansion room 25 mm, the impinging vortex room 14 mm, and the noise absorbtion room 10 mm. The results showed that it reduced noise by approximately 41.1 dB compared to the current systems available in the market. Furthermore, it showed reduced noise by approximately 12 dB more than a product with an acoustic absorber of the Fault Tamer(USA).

Absorption Characteristics of Micro-perforated Panel Absorber According to Incident Pressure Magnitude and Its Geometric Parameters (가진 음압 및 설계 인자에 따른 미세 천공판 흡음 기구의 흡음 특성)

  • Park, Soon-Hong;Seo, Sang-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.178-185
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    • 2011
  • The micro-perforated panel absorber (MPPA) is one of promising noise control elements because of its applicability to extreme environments where general porous materials cannot be used. Since the MPPA is inherently non-porous sound absorber, it can be a good candidate of acoustic protection system of a space launcher. The overall sound pressure level inside payload fairings of commercial launch vehicles is so high (around 140 dB OASPL) that the conventional linear impedance model cannot be directly applied to the design of the acoustic protection systems. In this paper an acoustic impedance models of a micro-perforated panel absorber at high sound pressure environment were reviewed and the use of the impedance on the practical design of MPPAs was addressed. The variation of absorption characteristics of MPPA was discussed according to the design parameters, e.g., perforation ratio, the minute hole diameter, the thickness of MPP and the incident sound pressure level.

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Absorption Characteristics of Micro-perforated Panel Absorber According to High Incident Pressure Magnitude and Variation of Geometric Parameters (높은 입사 음압 및 설계 인자의 변화에 따른 미세 천공판 흡음 기구의 흡음 특성)

  • Park, Soon-Hong;Seo, Sang-Hyun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.11
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    • pp.1059-1066
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    • 2011
  • The micro-perforated panel absorber(MPPA) is one of promising noise control elements because of its applicability to extreme environments where general porous materials cannot be used. Since the MPPA is inherently non-porous sound absorber, it can be a good candidate of acoustic protection system of a space launcher. The overall sound pressure level inside payload fairings of commercial launch vehicles is so high(around 140 dB OASPL) that the conventional linear impedance model cannot be directly applied to the design of the acoustic protection systems. In this paper an acoustic impedance models of a micro-perforated panel absorber at high sound pressure environment were reviewed and the use of the impedance on the practical design of MPPAs was addressed. The variation of absorption characteristics of MPPA was discussed according to the design parameters, e.g., perforation ratio, the minute hole diameter, the thickness of MPP and the incident sound pressure level.

Design of a Micro-perforated Panel Absorber at High Incident Sound Pressure (높은 입사 음압에서의 미세 천공판을 이용한 흡음 기구의 설계)

  • Park, Soon-Hong;Seo, Sang-Hyun;Jang, Young-Soon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.10
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    • pp.983-990
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    • 2010
  • Reduction of acoustic loads of space launch vehicles can be achieved by acoustic absorbers satisfying strict cleanness requirements. This limited the use of general porous materials and requires non-porous sound absorbers. Micro-perforated panel absorbers(MPPA) is one of promising sound absorbers satisfying the cleanness requirement for launch vehicles. However, its applicability was limited to low sound pressure levels according to the acoustic impedance model of micro-perforated panels. In this paper the applicability of micro-perforated panel absorbers at high incident sound pressure was investigated in experimental ways. The absorption characteristics of a micro-perforated panel absorber was simulated according to its design variables, e.g., minute hole diameters and aperture ratios. It was shown that optimal design can be readily done by using proposed design charts. Experiments were conducted to measure acoustic properties of the designed micro-perforated panel absorbers. The results showed that acoustic resistance increases rapidly as incident sound pressure level does but change of acoustic reactance can be neglected in a practical point of view. This caused the decrease of peak value of absorption coefficient at high incident sound pressure level, but the amount of reduction can be accepted in practice. The major advantage of the micro-perforated panel absorber(wide absorption bandwidth) was still kept at high sound pressure level.

Continous rail absorber design using decay rate calculation in FEM

  • Molatefi, Habibollah;Izadbakhsh, Soroush
    • Structural Engineering and Mechanics
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    • v.48 no.4
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    • pp.455-466
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    • 2013
  • In recent years, many countries have added railway noise to the issues covered by noise regulations. It is known that the rail is the dominant source of rolling noise at frequency range of 500Hz-2000Hz for the conventional speeds (<160km/h). One of the effective ways to reduce noise from railway track is using a rail vibration absorber. To study the acoustic performance of rail absorber, the decay rates of vibration have long been used by researcher. In this paper, A FE model of a periodic supported rail with infinite element in ABAQUS is developed to study the acoustic performance of the rail absorber. To compute the decay rates, acceleration responses along the rail transferred to MATLAB to obtain response levels in frequency domain and then by processing the response levels, the decay rates obtained for each1/3octav band. Continous rail absorber is represented by a steel layer and an elastomer layer. The decay rates for conventional rail and rail with one-side absorber and also, the rail with two side absorber are obtained and compared. Then, to improve the system of rail absorber, a steel plate with elastomer layer is added to bottom of the rail foot. The vertical decay rate results show that the decay rate of rail vibration along the track is significantly increased around the tuned frequency of the absorber and thus the rail vibration energy is substantially reduced in the corresponding frequency region and also effective in rail noise reduction.

A modal approach for the efficient analysis of a bionic multi-layer sound absorption structure

  • Wang, Yonghua;Xu, Chengyu;Wan, Yanling;Li, Jing;Yu, Huadong;Ren, Luquan
    • Steel and Composite Structures
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    • v.21 no.2
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    • pp.249-266
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    • 2016
  • The interest of this article lies in the proposition of using bionic method to develop a new sound absorber and analyze the efficient of this absorber in a ski cabin. Inspired by the coupling absorption structure of the skin and feather of a typical silent flying bird - owl, a bionic coupling multi-layer structure model is developed, which is composed of a micro-silt plate, porous fibrous material and a flexible micro-perforated membrane backed with airspace. The finite element simulation method with ACTRAN is applied to calculate the acoustic performance of the multi-layer absorber, the vibration modal of the ski cabin and the sound pressure level (SPL) near the skier's ears before and after pasting the absorber at the flour carpet and seats in the cabin. As expected, the SPL near the ears was significantly reduced after adding sound-absorbing material. Among them, the model 2 and model 5 showed the best sound absorption efficiency and the SPL almost reduced 5 dB. Moreover, it was most effctive for the SPL reduction with full admittance configuration at both the carpet and the seats, and the carpet contribution seems to be predominant.

Experimental Study of the Role of Gas-Liquid Scheme Injector as an Acoustic Resonator in a Combustion Chamber

  • Kim Hak-Soon;Sohn Chae-Hoon
    • Journal of Mechanical Science and Technology
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    • v.20 no.6
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    • pp.896-904
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    • 2006
  • In a liquid rocket engine, the role of gas-liquid scheme injector as an acoustic resonator or absorber is studied experimentally for combustion stability by adopting linear acoustic test. The acoustic-pressure signals or responses from the chamber are monitored by acoustic amplitude. Acoustic behavior in a rocket combustor with a single injector is investigated and the acoustic-damping effect of the injector is evaluated for cold condition by the quantitative parameter of damping factor as a function of injector length. From the experimental data, it is found that the injector can play a significant role in acoustic damping when it is tuned finely. The optimum tuning-length of the injector to maximize the damping capacity is near half of a full wavelength of the first longitudinal overtone mode traveling in the injector with the acoustic frequency intended for damping in the chamber. When the injector has large diameter, the phenomenon of the mode split is observed near the optimum injector length and thereby, the acoustic-damping effect of the tuned injectors can be degraded.

Dissimilar Friction Welding for Marine Shock Absorber Steels and its Evaluation by Acoustic Emission (해양차량 쇽업소버용 강재의 이종 마찰용접과 AE평가)

  • LEE BAE-SUB;KONG YU-SIK;KIM SEON-JIN
    • Journal of Ocean Engineering and Technology
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    • v.19 no.1
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    • pp.44-48
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    • 2005
  • The shock absorbers for marine vehicles are very important components to absorbing the shock resulting from driving. Depending on the kinds of vehicles, these essential components, piston and piston rod, must be made of S25C, S45C, and SCM440, must be precisely machined, and assembled by the bolts. Other materials used have been difficult to weld, and could be unstable in quality, by the conventional arc welding. Also, they have been associated with a lot of technical problems in manufacturing. However, using the friction welding technique, such problems will be avoided. These factors have necessitated the domestic development of the marine shock absorber using a friction welding, as well as stimulating a new approach to the study of real-time weld quality evaluation by AE techniques.

An Experimental Study on the Absorption Property of Slit Absorbers with Composite Details

  • Jeong, Dae-Up;Joo, Moon-Ki
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.2E
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    • pp.81-90
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    • 2002
  • Single absorbing materials and Helmholtz resonators have limited absorption characteristics over limited frequency ranges due to their structures and properties. Porous materials are highly absorptive for mid and high frequency ranges, while they have little sound absorption for low frequency sounds. Helmholtz resonators are generally used to absorb sound energy for a specified frequency range. Hence they have limited capability in controlling the overall acoustic properties of a space. Not much has been known about useful finishing materials which have enough rigidity and absorption over broad frequency range, in spite of wide demands from acoustic designers and consultants. The present work measured and analyzed absorption characteristics of a slit absorber by varying surface materials, depths of air gap, dimensions of slat and slit widths. It was found that the narrower the slit width, the larger the absorptions over the wide frequency ranges and the pattern was dependent on the presence of porous material. Narrower slat's width tend to increase the slit absorber's absorption more or less. Absorption coefficients at low frequency ranges were dramatically improved (from 0.23 to 0.56) by increasing air gap when porous materials were present.

The study of absorbing material performance for the noise mitigation of slab track (슬래브궤도의 소음저감을 위한 흡음재의 성능에 관한 연구)

  • Kim, Jin-Ho;Lee, Kwang-Do;An, Gang-Yell;Jun, Woo-Sang
    • Proceedings of the KSR Conference
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    • pp.1044-1049
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    • 2007
  • The construction of concrete slab track system is increased because the system has advantages which are maintenance free and so on, the other side, the system has weak points such as increase of the cost of the early stage construction and noise levels. The increment of noise is due to the reflection of generated noise on the slab tracks. Therefore the acoustic-absorptive materials are considered to reduce noise level. It has been made clear that acoustic-absorptive materials are effective for reducing the wheel/rail noise on slab tracks. The important performance of the acoustic-absorptive material is absorption rates and absorption rates are verified for the considered absorber elements using acoustic duct method. In addition, the required provisons for installing acoustic-absorptive block on slab tracks are considered.

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