• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.653-658
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• 2001

In this study, a new practical method of predicting the sound absorption coefficient for multiple perforated-plate sound absorbing system was developed using transfer matrix method. In order to validate the proposed method, the absorption coefficients calculated by transfer matrix method for single perforated plate were first compared with the absorption coefficients measured by SWR method according to different porosity, hole diameter, and thickness of the perforated plate. Based on the comparison results, transfer matrix method was further applied to double and triple perforated plates to evaluate the absorption coefficients. The experimental results showed that the absorption coefficients from transfer matrix method generally agreed well with the corresponding absorption coefficients from SWR method. However, due to the limitations of the impedance model used in this study, the measured values were differed with the calculated values for small porosity, hole diameter, and thickness in size of the perforated plate indicating the need of impedance model development for multiple perforated-plate sound absorbing system covering wide ranges of porosity, hole diameter, and thickness of the perforated plate.

• 한국측량학회지
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• 제35권4호
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• pp.231-240
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• 2017

This paper aims to study a method to estimate precise carbon absorption by quantification of forest information that uses accurate LiDAR data, hyperspectral image. To estimate precise carbon absorption value by using spatial data, a problem was found out of carbon absorption value estimation method with statistical method, which is already existed method, and then offered optimized carbon absorption estimation method with spatial information by analyzing with methods of compare digital aerial photogrammetry and LiDAR data. It turned out possible Precise classification and quantification in case of using LiDAR and hyperspectral image. Various classification of tree species was possible with use of LiDAR and hyperspectral image. Classification of hyperspectral image was matched in general with field survey and Mahalanobis distance classification method. Precise forest resources could be extracted using high density LiDAR data. Compared with existing method, 19.7% in forest area, 19.2% in total carbon absorption, 0.9% in absorption per unit area of difference created, and improvement was found out to be estimated precisely in international code.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.700-702
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• 2003

A new method for automatic detection of absorption features is proposed. This method is based on the modulus maximum of the scale-space image calculated by continuous wavelet transform. This method is computationally efficient as compared to traditional methods. The continuum removal algorithm is than implemented on the detected absorption features to reduce some additive factors caused by other absorbing of materials. The results show that the chlorophyll absorption features are detected exactly.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.709-716
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• 2002

A practical method of predicting the sound absorption coefficient for multiple perforated-plate sound absorbing system was developed using transfer matrix method. The proposed method was validated by comparing the calculated absorption coefficients of a single layer perforated plate with the values measured by the two-microphone impedance tube method for various porosity and spacing of the perforated plate. The developed transfer matrix method was further applied to estimate the multiple layer perforated plates and it is shown that the estimated absorption coefficients agree well with the measured values.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.280-285
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• 2008

The helmholtz resonator with the perforated neck has demerits that the absorption performance is not so outstanding in an anti-resonance frequency and high frequency bandwidth. In order to overcome these problems, in the paper, a resonator combined with porous material is proposed. The absorption performances of resonators are measured by two-microphone method and estimated by transfer matrix method. The experimentally measured values of normal absorption coefficients agree well with the corresponding values from the transfer matrix method. Because of the porous material, it is shown that the absorption performance have been significantly improved in the anti-resonance frequency and high frequency bandwidth.

• 한국소음진동공학회논문집
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• 제19권6호
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• pp.628-633
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• 2009

The helmholtz resonator with the perforated neck has demerits that the absorption performance is not so outstanding in an anti-resonance frequency and high frequency bandwidth. In order to overcome these problems, in the paper, a resonator combined with porous material is proposed. The absorption performances of resonators are measured by two-microphone method and estimated by transfer matrix method. The experimentally measured values of normal absorption coefficients agree well with the corresponding values from the transfer matrix method. Because of the porous material, it is shown that the absorption performance have been significantly improved in the anti-resonance frequency and high frequency bandwidth.

• 한국소음진동공학회논문집
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• 제18권1호
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• pp.71-79
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• 2008

A helmholtz resonator has been widely used for the purpose of suppressing the low frequency noises propagated from various heat and fluid machineries. However, the conventional resonator has demerits that the effective absorption bandwidth is narrow and the absorption performance is not so outstanding in the only limited configurations of neck and cavity as well. In order to overcome these problems, in this paper, a resonator with perforated neck is proposed. The absorption performances of the resonator are measured by two-microphone method and estimated by transfer matrix method. The measured values of normal absorption coefficients agree well with the estimated values. By introducing the perforated plates at the neck of a resonator, it is shown that the absorption performance have been significantly improved.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1317-1324
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• 2011

대기중에 부유하고 있는 입자들의 광흡수량을 측정할 수 있는 기법을 소개한다. 본 연구에서 사용된 기법은 광열분광법이다. 광흡수 측정에 있어서 광열 기법의 장점은 광산란에 둔감할 뿐만 아니라 광산란 계수의 영향을 받지 않고 광흡수 계수를 직접적으로 측정할 수 있다는 것이다. 공기중 부유물질의 흡수 계수 측정의 시간 상수는 10 초이며, 실시간으로 고속도로 주변에서 흡수 계수를 측정하였다. 자동차 경주용 트랙, 공항, 또는 연구소 정문 등 차량 통행량이 많은 지역에서의 흡수 계수가 높게 측정되었는데, 이는 카본 부유물 입자에 의한 영향이라고 판단된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1341-1346
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• 2001

In this study, the acoustic properties of steel-wire sound absorbing materials with different thickness and bulk density were investigated in terms of characteristic impedance, propagation constant, and absorption coefficient. The well-known two-cavity method was used for evaluating those acoustic parameter values in experiments. Also, in order to validate the experimentally measured values, the results were compared with the results obtained from Chung and Blaser's transfer function method and SWR method. The experimentally measured values of normal absorption coefficients were generally agreed well with the corresponding values from the transfer function method and the SWR method. Based on the experimental results, the following conclusions could be made. The magnitude of the absorption coefficient and the frequency range of the maximum absorption coefficient were controllable by changing the thickness and bulk density of the sound absorbing materials. Also, the magnitude of the absorption coefficient depended on the characteristic impedance and the propagation constant. As large as the air cavity depth at the rear side of the steel-wire sound absorbing materials, the maximum magnitude of the absorption coefficient occurred at the lower frequency ranges.

• 산업기술연구
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• 제41권1호
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• pp.15-20
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• 2021

This work proposes a simple method to use the added absorption per person values to predict the expected values of the acoustical conditions in occupied classrooms. This method is based on the effects of the values of added absorption per person on the unoccupied total absorption values of the classrooms and on other room acoustical parameters. The total sound absorption in an unoccupied classroom can be calculated from measured reverberation times in the classroom. The expected occupied absorption can be calculated using equation which was obtained in a previous study (Choi, 2017) by fitting a linear regression line to a plot of total occupied absorption versus the corresponding unoccupied total absorption values measured in 12 university classrooms. The ratios of occupied-to-unoccupied sound absorption are used to predict increments in the values of acoustical parameters that result when occupants are added to the rooms.