• Title/Summary/Keyword: noise reduction coefficient (NRC)

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Sound Absorption Performance of Noise Barrier According to Single Number Rating Methods (단일수치 평가방법에 따른 방음벽의 흡음성능 고찰)

  • Kim, Yonghee;Lee, Sungchan
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.27 no.2
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    • pp.243-250
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    • 2017
  • In this study, single number rating methods of sound absorption coefficients are discussed. After that the sound absorption performance of noise barriers which are classified by Korea Standard are analyzed according to several standards. The existing rating methods such as NRC (noise reduction coefficient), SAA (sound absorption average) or ${\alpha}_w$ (weighted sound absorption coefficient) from ASTM C423, KS F 3505 and ISO 11654 are introduced. The sound absorption performance of noise barrier is evaluated to compare NRC and ${\alpha}_w$ value. When the value is over 0.6 there are large variance between NRC and ${\alpha}_w$ value. As results, it is needed to unify single number rating methods of sound absorption coefficients for Korean standards on sound absorbing materials.

Experimental study of reverberation time in ship's public area (선박의 공용구역 잔향시간의 실험적 연구)

  • Kim, Taemoo;Choi, Choongyoung;Park, Nojun;Park, JeanHyung;Kwun, Hyuk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.242-242
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    • 2013
  • Recently, importance of working environment is increased in commercial vessel and offshore structure. Marine facility design and ambient environment condition are influenced to enhancing human performance and reducing human errors. Consequently, the quality of accommodation where offshore facility crews sleep, eat and relax will influence their job performance and overall sense of comport and well-being. Therefore, adequate acoustic isolation between adjacent spaces is normally required to achieve satisfactory internal noise levels, acoustic privacy and speech intelligibility. In this study, the reverberation time is investigated in the public areas where there are not provided the information of material's noise reduction coefficient (NRC). The experiment of reverberation time is rarely performed for the various type public areas in a marine structure. Therefore, the reverberation time in a vessel is investigate in order to evaluate the room's noise reduction coefficient (NRC) in a public area.

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Sound Absorption of Natural Fiber Composite from Sugarcane Bagasse and Coffee Silver Skin

  • Wachara KALASEE;Putipong LAKACHAIWORAKUN;Visit EAKVANICH;Panya DANGWILAILUX
    • Journal of the Korean Wood Science and Technology
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    • v.51 no.6
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    • pp.470-480
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    • 2023
  • This study aimed to develop a sound-absorbing composite using sugarcane bagasse (SB) and coffee silver skin (CS) as raw materials. The composite boards were manufactured by bonding the fibers with Melamine Urea-Formaldehyde adhesive, ensuring a consistent thickness of 30 mm. Various densities were employed, namely 380, 450, and 520 kg/m3. The samples were fabricated with different fiber ratios, including SB100%, SB75% with CS25%, and SB50% with CS50%. The sound absorption coefficient (SAC) and noise reduction coefficient (NRC) were measured using the impedance tube method within a frequency range of 63-6,300 Hz. The experimental results revealed that the mixing ratio of CS exerted a notable influence on enhancing the SAC, while the density of the composite board exhibited a significant impact on increasing both the SAC and NRC. Among the densities tested, the optimal value was observed at 520 kg/m3, yielding a SAC value of 0.65 at a frequency of 1,000 Hz and an NRC value of 0.55 for the SB50-CS50 composite plate. These findings underscore the importance of considering the CS mixing ratio and composite board density when aiming to optimize sound absorption properties.

Absorption Characteristics of Sound Proof Wall by Scrap Aluminum and Perforated Plate (알루미늄칩과 타공판을 이용한 방음벽 충진재의 흡음특성)

  • Lee, Young-Jung;Kim, Dae-Gun;Park, Kyung-Hwa;Kim, Young-Do
    • Korean Journal of Materials Research
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    • v.19 no.7
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    • pp.382-385
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    • 2009
  • Efforts to reduce noise in industrial application fields, such as automobiles, aircrafts, and plants have been gaining considerable attention while a sound proof wall to protect people from the noise has been intensively investigated by many researchers. In this study, our research group suggested creating a new sound proof wall composed of scrap aluminum chips and perforated plates in a commercial polyester sound proof wall, which was then successfully fabricated. This wall's sound absorption characteristics were measured by an impedance tube method. The sound absorption property was evaluated by measuring the Noise Reduction Coefficient (NRC) to the standard, ASTM C 423-90a. The noise reduction coefficient of the sound proof wall composed of 3.5 vol.% and 7.5 vol.% of scrap aluminum chips relatively increased to 5% and 8% compared to the commercial polyester sound proof wall. The scrap aluminum perforated plate also relatively increased to 13% compared to the commercial polyester sound proof wall.

A Study on the Development of Sound Absorption Material Using Perlite for Noise Barrier Wall (펄라이트를 이용한 방음벽의 흡음소재 개발에 관한 기초적 연구)

  • Jo, Young-Kug;Yang, Ju-Kyung
    • Journal of the Korea Concrete Institute
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    • v.20 no.5
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    • pp.653-660
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    • 2008
  • The purpose of this study is to analyze the optimal mix design of the sound absorption material that is made from perlite and various binder systems for noise barrier wall. The polymer cement slurry which is made from two types of polymer dispersions, and silicone type inorganic material are used as binder. The test specimens are prepared with various polymer cement ratios, binder ratios, and tested for strengths, freezing and thawing and sound absorption performance by the tube and the reverberation room methods. From the test results, the difference of sound absorption coefficient by the tube method is a little recognized, however, noise reduction coefficient (NRC) of test specimens bound by the polymer cement slurry is in the ranges of 0.48 to 0.51. They are a little higher than those bound by cement only, and are lower values than recommended value of 0.7 by the Ministry of Environment. However, the sound absorption coefficient of test specimens at low frequency range of 250 to 500 Hz by reverberation room method shows very high values as 0.84 to 1.00, and 0.57 to 0.77 at the high frequency. The test specimens with polymer cement slurry binder have a good balance between performance and cost, and have proper properties in strengths, freezing and thawing resistance as sound absorption material for noise barrier wall. It is apparent that the good sound absorption material can be produced according to the optimum mix design that is recommended from this study.

Evaluations of the Acoustics Characteristics of Cellulose Absorbers (셀롤로오즈 흡음재의 음향적 특성 평가)

  • Yeon, Joon-oh;Kim, Kyoung-woo;Yang, Kwan-seop
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.760-765
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    • 2013
  • Eco-friendly material applied to building would be one of the materials which is must developed for global environmental conservation and reduction of carbon dioxide. For development of eco-friendly material, a cellulose sound-absorbing material has been developed with waste paper through adjustment of various mix proportions. The developed cellulose sound-absorbing material has been tested for its acoustic properties such as acoustic absorptivity and dynamic elastic modulus. The absorptivity was evaluated by developing six samples and using impedance tube and reverberation chamber. As a result of the evaluation, 0.64(NRC) was secured in absorptivity and $4.7MN/m^3$ was indicated in dynamic elastic modulus. Also, for practical use of developed sound-absorbing material as inner heartwood in drywall, comparison test of sound reduction index was performed with existing glass wool sound-absorbing material and constructed drywall of gybsum board. The results have shown 55dB(Rw) of sound reduction index in glass-wool wall and 46dB(Rw) in cellulose.

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Evaluations of the Acoustics Characteristics of Cellulose Absorbers (셀룰로오즈 흡음재의 음향적 특성 평가)

  • Yeon, Joon-Oh;Kim, Kyoung-Woo;Yang, Kwan-Seop
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.5
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    • pp.456-462
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    • 2013
  • Eco-friendly material applied to building would be one of the materials which is must developed for global environmental conservation and reduction of carbon dioxide. For development of eco-friendly material, a cellulose absorber has been developed with waste paper through adjustment of various mix proportions. The developed cellulose absorber has been tested for its acoustic properties such as absorption coefficient and dynamic stiffness. The absorption coefficient was evaluated by developing six samples and using impedance tube and reverberation chamber. As a result of the evaluation, 0.64(NRC) was secured in absorption coefficient and 4.7 $MN/m^3$ was indicated in dynamic stiffness. Also, for practical use of developed absorbers as inner heartwood in drywall, comparison test of sound reduction index was performed with existing glass wool absorbers and constructed drywall of gypsum board. The results have shown 55 dB(Rw) of sound reduction index in glass-wool wall and 46 dB(Rw) in cellulose.

The study on the management method and installation guide of temporary noise barrier (가설방음벽의 운영방안 및 설치기준에 관한 연구)

  • Yoon, Je-Won;Kim, Young-Chan;Kang, Hee-Man;Jang, Tae-Soon;Lee, Ki-Jung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.372-375
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    • 2006
  • 건설 공사장에서 발생하는 건설장비의 소음을 저감하여 공사장 인근 지역의 생활환경에 미치는 소음영향을 최소화할 수 있도록 건설업체에서는 최대한의 노력으로 가설방음벽을 설치 운영하고 있으나, 설치된 가설방음벽의 효과분석 및 운영방법에 대한 검토가 부족하여 효율적인 소음저감대책으로서의 가설방음벽 운영이 어려운 실정이다. 따라서, 본 연구에서는 가설방음벽의 기초데이터의 확보와 소음해석을 통한 효율적인 운영방안을 제시하며, 설치기준에 관한 방안을 제시하고자 한다.

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Investigation of Test Methods for the Performance Assessment of Noise Barriers (방음벽의 성능평가를 위한 시험방법의 검토)

  • 윤제원;김두훈;김영찬;장강석;김대현
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.449-455
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    • 2001
  • 도로교통소음의 저감을 위해 설치되는 방음벽의 성능평가를 위해서는 흡음률 및 투과손실과 같은 음향성능에 대한 평가뿐만 아니라, 풍압 및 충격하중과 같은 구조성능과 방음판 제작에 사용되는 재질에 관한 성능평가도 수반되어야 한다. 따라서, 본 논문에서는 이러한 방음벽의 성능평가를 위한 음향 구조 및 재질에 관한 시험 및 평가방법을 제시하였다.

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A Study on the Characteristic of Sound Absorption of the Polyester Non-Woven Fabrics Used for the Automobile Sound Absorption Material (폴리에스터 부직포를 이용한 자동차용 흡음재의 흡음특성에 관한 연구)

  • 변홍식;이태관
    • Polymer(Korea)
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    • v.25 no.3
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    • pp.427-434
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    • 2001
  • The sound absorption materials With polyester (PET) were prepared for automobile. They consist of 3 layers with different size of PET fiber (3 and 15 deniers) in order to optimize the characteristic of sound absorption, and with various densities (895~1790 g/$cm^2$) by controlling the weight of PET of each layer. They were also compared with the commercial sound absorption materials made of glass wool. It was shown that the new PET had better absorption capability in both high and low frequency regions than that of the commercial material. It was revealed also that the density and the thickness of PET played an important role to determine the capability of sound absorption. The NRC (noise reduction coefficient) was increased by 22-39% with optimized PET sound absorption material. It should be noted that the PET can substitute the glass wool, a commercial sound absorption material, in view of environment and as well as recycle capability of sound absorption.

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