Sound Absorption Properties of Sound Absorption Materials Using Zelkova serrata Leaves

배은지,고준호,염다혜,Kyung-Rok Won,공이근,변희섭 강원대학교 산림과학연구소 2024 Journal of Forest Science Vol.40 No.2

This study analyzes the characteristics of sound-absorbing materials made from forest by-products of the deciduous tree species Zelkova serrata (Z. serrata) by evaluating their sound absorption performance. Accordingly, sound-absorbing materials with varying sample thicknesses, leaf sizes, and drying conditions were fabricated. The sound absorption properties were measured using the impedance tube method via middle-type measurement tube (100 Hz-3,200 Hz). The sound absorption properties were evaluated using the average sound absorption coefficient (ASAC), which was calculated from the measured sound absorption coefficients at 250 Hz, 500 Hz, 1,000 Hz, and 2,000 Hz. The ASAC value significantly improved as the leaf size increased to 0.5×0.5 cm2, 1.0×1.0 cm2, and 2.0×2.0 cm2. The ASAC values under the two drying conditions were similar. There was no significant difference in ASAC according to the leaf size under the air-dried leaf condition, with a thickness of 2.50 cm. The highest ASAC value according to the sound-absorbing material thickness was 0.47 at a thickness of 2.50 cm and leaf size of 2.0×2.0 cm2 under the air-dried leaf condition. In addition, the variation in ASAC was 0.23, indicating that the sound absorption performance according to leaf thickness was more significant than the difference in absorption properties according to leaf size. A sound absorption coefficient (SAC) of 0.4 or higher was observed across the measurable frequency band (100 Hz-3,200 Hz). Furthermore, the SAC values with respect to leaf size and thickness were close to 1 in the high-frequency range above 2,000 Hz. Therefore, it is considered that sound-absorbing materials using Z. serrata leaves are advantageous in the field of absorbing noise in a high-frequency band of 2,000 Hz or more, and it is better to manufacture a thickness of 2.50 and 2.0×2.0 cm2.

방음판의 흡음률 측정방법 제안을 위한 기초 연구

오양기,김하근 한국음향학회 2023 韓國音響學會誌 Vol.42 No.2

Sound barrier walls are the most basic way to cope with noise problems in urban residential environments. The most important acoustic function of sound insulation board is represented by sound transmission loss and sound absorption coefficient. However, Korea has not yet established a standard for measuring the sound absorption rate of sound insulation boards. In addition, even in the European standard, where the overall acoustic standard of soundproofing boards has already been established, the sound absorption rate is applied only to the standard for measuring the sound absorption rate of general building finishing materials, and a separate measurement method considering the characteristics of soundproof walls and soundproofing boards is not presented. The sound absorption coefficient should be evaluated by summing up the energy absorbed into the material as well as the energy transmitted through the material, but the current European standard has a problem in that the transmitted sound energy is not taken into account. In this paper, we reviewed the sound absorption coefficient measurement standards of sound insulation boards currently being presented, and verified the difference between the results and the new measurement method considering transmission sound for sound insulation boards actually used in Korea. 방음벽은 도시 주거환경의 소음문제에 대응하기 위한 가장 기본적인 방법이다. 방음판의 가장 중요한 음향적기능은 음향투과손실과 흡음률로 표시된다. 특히 주거시설이 밀집되어있는 도심구간의 철도나 간선도로에서 원하지않는 반사음에 의한 2차 소음 문제를 최소화하기 위하여는 방음판의 흡음성능이 중요하다. 그러나 아직까지 우리나라는 방음판의 흡음률 측정방법에 관한 규격이 마련되어있지 않다. 또한 방음판의 전반적인 음향규격이 이미 만들어져있는 유럽규격에서조차 흡음률에 관해서는 일반적인 건축마감재료의 흡음률 측정기준을 준용하고 있을 뿐, 방음벽과방음판의 특성을 감안한 별도의 측정방법을 제시하지 못하고 있다. 흡음률은 재료의 내부로 흡수된 에너지 뿐 아니라재료를 투과한 에너지까지 합산하여 평가되어야 하는데 현재의 유럽규격은 투과음 에너지를 감안하지 못하고 있는문제를 안고 있다. 이 논문에서는 현재 제시되고 있는 방음판의 흡음률 측정 규격에 대해 고찰하고, 우리나라에서 실제 사용되고 있는 방음판을 대상으로 투과음을 감안한 새로운 측정방법과의 결과 차이를 검증하였다. 아울러 새로운 방음판 흡음률 측정규격의 마련을 위한 기초적 아이디어를 제시하였다.

Sound Absorption Capability of Medicine Herb Residues Mat

Eun-Suk Jang,Nam-Ho Lee,Chun-Won Kang 한국펄프·종이공학회 2023 펄프.종이기술 Vol.55 No.4

This study investigated the sound-absorbing properties of herbal medicine waste (HMW) as a promising eco-friendly material for sound absorption. The authors examined the sound absorption coefficient by filling impedance tubes with varying heights of HMW (4 cm, 6 cm, 8 cm, and 10 cm). The results revealed that at a filling height of 4 cm, the optimal sound absorption frequency was found to be 1416 Hz, with a sound absorption coefficient of 0.999. Similarly, at a filling height of 12 cm, the optimal sound absorption coefficient was 0.965 at 456 Hz. It was observed that the sound-absorbing performance at lower frequencies improved as the thickness of the sound-absorbing material increased. Based on the standards established in KS F 3503, HMW would receive a sound absorption grade of 0.5M to 0.7M, depending on the filling height. In conclusion, HMW showed excellent potential as a sound-absorbing material, and the results of our testing showed that it can be used as an alternative to synthetic fibers.

A model for the sound absorption coefficient of multi-layered elastic micro-perforated plates

Kim, Hyun-Sil,Ma, Pyung-Sik,Kim, Sang-Ryul,Lee, Seong-Hyun,Seo, Yun-Ho Academic Press 2018 Journal of Sound and Vibration Vol.430 No.-

<P><B>Abstract</B></P> <P>In this paper, a model for the sound absorption coefficient of multi-layered elastic micro-perforated plates (MPPs) in an impedance tube is developed using an analytical approach. Under the plane wave condition, a low-frequency solution is derived by including the symmetric modes of the plate vibration and the sound pressure field. The sound absorption model derived in this study can handle multi-layered structures composed of any combination of thin elastic plates with or without micro-perforations and rigid MPPs. The effects of the parameters of the plate thickness, hole diameter, perforation ratio, cavity depth, and damping on the sound absorption capabilities are described. For a single MPP, when the perforation ratio is very small, it is observed that the combined effect of the elastic behavior and micro-perforation results in a significant increase of the sound absorption coefficient compared to that of a rigid MPP. However, when the perforation ratio is order of a few percent, the effect of the elastic behavior is negligible compared to that of micro-perforations. Some guidelines for selecting optimum parameters to achieve the maximum average sound absorption coefficient for a given frequency band are discussed for double- and triple-elastic MPPs. It is important to ensure that the perforation ratio of the last MPP is small such that the elastic behavior is dominant, while for the first MPP (and for the second MPP in the triple configuration), the elastic behavior should not be dominant. In addition, maintaining equal cavity depths is beneficial for a high average sound absorption coefficient.</P>

Sound Absorption Coefficients of Micro-fiber Fabrics by Reverberation Room Method

Na, YoungJoo,Lancaster, Jeff,Casali, John,Cho, Gilsoo Sage Publications 2007 Textile research journal Vol.77 No.5

<P>The sound absorption properties of materials are important not only for noise reduction, but also for controlling reverberation time for speech intelligibility in rooms and for promoting fuller sound in concert halls. Industrial textiles are focusing on these materials' application for sound absorption, thus new textiles were to be examined in relation to this performance. Micro-fiber fabric has fine fibers and a high surface area and it has been used in such applications as wipers, thermal insulator, filters or breathable layers. It can be also used for sound absorption. This paper examines the possibility of using micro-fiber fabrics as sound absorbent materials. We tested the sound absorption coefficients of five micro-fiber fabrics and one regular fiber fabric by the reverberation room method. The results showed that the micro-fiber fabrics' sound absorption is superior to that of conventional fabric with the same thickness or weight, and the micro-fiber fabrics' structure was found to be important for controlling sound absorption according to sound frequency. Fabric density was found to have more effect than fabric thickness or weight on sound absorption, and the Noise Reduction Coefficient increases to its highest value at a fabric density of about 0.14 g/cm3, and it decreases thereafter.</P>

Peanut Shells as an Environmentally Beneficial Sound-Absorbing Material

장은석 한국목재공학회 2022 목재공학 Vol.50 No.3

This study investigated the prospect of using peanut shells as an alternative and green sound-absorbing material. The sound-absorption coefficients were determined after filling impedance tubes of 30, 60, and 90 mm in height with peanut shells. The sound-absorption ability increased as the filling height increased, showing noise reduction coefficient (NRCs) of 0.23, 0.43, and 0.54 for the 30-, 60-, and 90-mm heights, respectively. In addition, for sounds greater than 2,000 Hz, the average sound-absorption coefficient of peanut shells in the 60- and 90-mm heights was 0.9. In summary, peanut shells were found to have good sound-absorption properties comparable to or better than those of bamboo, sisal, jute, and wool, and this research suggests that peanut shells may be useful as an environmentally friendly sound-absorbing material.

Use of Pine (Pinus densiflora) Pollen Cones as an Environmentally Friendly Sound-Absorbing Material

장은석 한국목재공학회 2022 목재공학 Vol.50 No.3

This study examined the utility of pine (Pinus densiflora) pollen cones as an environmentally friendly material with sound-absorbing properties. Pine pollen cone samples with widths of 0.8–1.2 cm and lengths of 3.5–4.5 cm were prepared. After filling impedance tubes to heights of 6, 8, 10, or 12 cm with the pine pollen cones, the sound absorption coefficient of the pine pollen cones was investigated. The peak sound absorption frequency of the samples with a thickness of 6 cm was reached at 1,512 Hz; however, this value shifted to 740 Hz in samples with a thickness of 12 cm. Therefore, the sound-absorbing performance of pine pollen cones at low frequencies improved as the material thickness increased. According to KS F 3503 (Korean Standards Association), the sound absorption grade of pine pollen cones ranges from 0.3 to 0.5 M, depending on the material thickness of the pine pollen cones. In conclusion, the pine pollen cones demonstrated good sound absorption properties. They, thus, may be considered an environmentally friendly sound-absorbing material.

시험방법에 따른 흡음률 비교

이재원(Lee, J.W.),구진회(Gu, J.H.),박형규(Park, H.K.),강대준(Kang, Dae-Joon) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.5

Today, the use of the sound absorptive material is increasing to improve the room acoustics in the auditorium and music hall, etc. Usually, the sound absorption materials have been used to enhance the performance of a noise barrier and improve the room acoustics in construction site. Generally, the sound absorbtion coefficients are the most important factor reflecting the sound absorbtion performance. There are two methods to measure the sound absorption coefficient. The first one is the reverberation room method, and the second is the impedance tube method. In this study, we measure the sound absorbtion coefficients using these two methods, and then we compared the results of the sound absorbtion coefficients to look into the difference of results between reverberation room method and impedance tube method. Also we compared the results of the sound absorbtion coefficients with respect to the size of sample and the volume of reverberation room. From the experiment, we could see that the sound absorbtion coefficients are measured equally for different sample size. But the sound absorbtion coefficients are measured differently according to test methods and test conditions.

Effect of the suspended ceiling with low-frequency resonant panel absorber on heavyweight floor impact sound in the building

Ryu, Jongkwan,Song, Hansol,Kim, Yonghee Elsevier 2018 Building and Environment Vol.139 No.-

<P><B>Abstract</B></P> <P>This study investigated the effect of the suspended ceiling panel with low-frequency resonant panel absorber on heavyweight floor impact sound. The resonant panel absorber was designed with a perforated top panel, an air gap with or without glass wool, and a bottom panel to ensure a high absorption coefficient in the low-frequency range around 100 Hz. Absorption coefficient measurements were carried out first in the reverberation chamber for resonant panel absorbers varying with the hole diameter of the top panel, the thickness of the glass wool and the air gap between the top and bottom board. As a result, the glass wool had the greatest influence on the absorption coefficient, and the highest absorption coefficient of the resonant panel absorber was about 0.6 in the band of 100 Hz. Floor impact sounds after installing the suspended ceiling with the best resonant panel absorber were also measured in test building using heavyweight floor impact sound sources (bang machine and rubber ball) and compared with result for normal suspended ceiling with gypsum board. Heavyweight floor impact sound by the resonant panel absorber was decreased by 2 dB and 4 dB in single number quantity (<I>L</I> <SUB>i,Fmax,Aw</SUB>) for bang machine and rubber ball, respectively. In particular, the resonant panel absorber reduced by 6 dB in 125 Hz octave band with the largest absorption coefficient.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Suspended ceiling with resonant panel absorber reduces heavyweight floor impact sound. </LI> <LI> Glass wool has significant influence on resonance frequency of resonant panel absorber. </LI> <LI> Effect of glass wool in resonant panel absorber depends on hole diameter. </LI> <LI> Resonant panel absorber diminishes air-spring effect in space above ceiling. </LI> </UL> </P>

Comparison of Transfer Function Method and Reverberation Room Method in Measuring the Sound Absorption Coefficient of Rice Straw Particle Mat

( Chun-won Kang ),( Eun-suk Jang ),( Sang-sik Jang ),( Ho-yang Kang ) 한국목재공학회 2018 목재공학 Vol.46 No.4

This study estimates the sound absorption capability of rice straw particle mats by two methods: the transfer function method and the reverberation room method. In the reverberation method, the central frequency was set to the one-third octave band in the 100-5000 Hz range; in the transfer function method, the frequency range was 500-6400 Hz. Both methods yielded similar noise reduction coefficients of the rice straw mats. The noise reduction coefficient was approximately 0.8, indicating a high sound-absorption property of the mats. Therefore, rice straw matting is a suitable candidate material for sound-barrier walls against highway noise.