선박 및 수중구조물의 고속, 대형화 및 요구조건 강화의 추세에 따라 유동소음 예측기술의 중요성이 강조되고 있다. 항공, 철도 등의 공력소음 분야에서는 음향상사법을 이용하여 순음 및 광대역 유동소음에 대해 활발히 연구되고 있는 반면 조선해양분야에서는 수중추진기의 날개주파수소음에 대해서만 일부 고려되고 있다. 본 논문에서는 날개면 형상의 주요 유동소음발생 메커니즘 뒷날소음을 고려 가능한 FW-H Formulation 1B를 이용하여 수중추진기 및 선저부가물의 기초요소인 수중익에 대해 광대역소음 예측기법을 연구하였다. 기존의 FW-H Formulation 1B는 공기 중의 압력상관관계 모델에 기반하여 구성되어 있어 매질에 대한 일반성 및 정확도의 한계를 가지므로 수중환경에 대해 일반성을 가지는 벽면변동압력 모델로 확장하는 방법론을 제시하였다. 공기 중 날개면의 소음계측결과와 비교해 벽면변 동압력 모델을 이용할 경우 기존모델의 해석결과 대비 5 dB 이내의 오차로 정확도 관점에서의 유용성을 확인할 수 있었으며 전산유체역 학과 벽면변동압력을 이용한 수중환경의 광대역소음해석 절차를 확립하고 수중익의 광대역소음 예측을 수행하였다.

수중에서 빠른 속도로 운동하는 물체 주변에서 감압이 발생하며, 이로 인해 공동 핵이 팽창함으로써 캐비테이션이 발생한다. 캐비테이션이 발생하게 되면 소음 및 진동이 증가하며, 추진기의 경우 추진 성능이 저해되는 악영향을 초래하기 때문에 이에 대한 예측이 필요하다. 본 연구에서는, 캐비테이션 발생으로 인한 공동소음의 해석절차를 정립하고, 타원형 날개에 적용하였다. 먼저 전산유체역학 해석을 수행하여, 날개 형상 주위 유동장 정보를 도출하였다. 공동 핵 밀도 함수를 활용하여, 핵의 초기 반경 별로 개수를 계산하였고 이들을 압력 강하가 큰 날개 끝 전류에 랜덤하게 배치하였다. 이후 공동소음 해석을 위해 각각의 핵에 대하여 Lagrangian 관점에서 버블 다이나믹스를 활용하였고, 계산된 공동의 거동으로부터 소음해석을 수행하였다. 공동소음은 광대역 소음의 특성을 가지는 것을 확인하였으며, 최종적으로 선박해양플랜트연구소(KRISO)의 대형캐비테이션터널(LCT)에서 수행된 실험 계측결과와의 비교를 통해 검증을 수행하였다.

PURPOSES : This paper is aimed at suggesting a novel approach for determining the pavement condition rating based on the tire-surface friction noise using a machine learning algorithm as a low-end pavement condition monitoring system. METHODS : Vehicle on-board type noise measurement system according to the ISO11819-2, and the K-nearest neighbors with dynamic time warping algorithm were applied. The system and algorithm were empirically tested with a field study. RESULTS : The developed AI- and noise-based pavement condition monitoring system demonstrated significantly positive results with a precision 90.8%, recall 84.8%, and f1-score 86.1%. CONCLUSIONS: We herein confirmed that the acoustic property between the tire and road surface can be used for monitoring pavement conditions. It is believed this finding presented a new paradigm for monitoring pavement conditions based on visual information. However, extensive studies focused on the practical application of this method are required.

It is well-known that the primary role of a vehicle exhaust system is to reduce the exhaust emissions and noise caused by a running vehicle. However, as vehicle exhaust systems are being evaluated and improved in various ways to satisfy consumer needs, technologies for reducing noise and vibration are significantly being developed. The biggest challenge in designing an exhaust system is generating the optimal back pressure and flow velocity for a running vehicle, thereby maximizing the performance, while simultaneously reducing the noise caused by the exhaust emissions. In this study, we designed the junction chamber shapes of various exhaust systems, which are applicable to V6 and above engines, and conducted a CFD analysis of the exhaust gas flowing through an exhaust pipe. In addition, we precisely measured the noise and vibration caused by a vehicle and analyzed the correlation.

Of the daily noises, construction noises cause serious conflicts between a construction firm and residents due to their high sound pressure level and shocking, repetitive sound. While South Korea regulates construction noises on the basis of legal criteria to minimize the damage from the noises, the regulation only involves a weighted sound level (dB(A)), which is loudness, like other types of noises. However, since construction noises are characterized by very diverse spectra and waveforms, it has been indicated that they cannot be reflected only by physical loudness: SPLdB(A). In addition, the need to reflect acoustic psychological characteristics and meanings of human beings in evaluating construction noises has recently been indicated. This study aimed to use six Zwicker parameters to determine the sound quality and acoustic psychological characteristics of construction noises and analyze the correlation between physical indexes of construction noises, as found in literature review, and the Zwicker parameters. Loudness of construction noises were closely correlated with SPLdB(A); shocking noises were perceived as ‘loud, sharp, and annoying’ sound. The Zwicker parameters were most strongly correlated with loudness, followed by unbiased annoyance and sharpness, among the evaluation indexes; as for correlation with construction noises, ‘normal noises’ were closely correlated with loudness, ‘shocking noises’ were closely correlated with loudness, unbiased annoyance, and sharpness, and ‘fluctuating noises’ were closely correlated with loudness. Therefore, if loudness, unbiased annoyance, and sharpness were taken into account in terms of the sound quality in evaluating construction noises, it is expected to be useful to make and revise criteria for regulating the noises.

This study investigates the noise characteristics of small DC motors and applies them to the production line of small DC motors to qualify. Because currently the noise and vibration are greatly reduced due to vibration reduction technology and sound insulation technology of engine and transmission development. For this reason, the noise and vibration problems of various small DC motors that have not been heard before are emerging. For this purpose, noise characteristics of good and bad products of company A and B which are most used at present are analyzed and noise characteristics are investigated.

Noises in each construction field cause residents in the neighborhood to make complaints due to their high sound pressure level and repetitive, shocking sound. While South Korea regulates construction noises on the basis of legal criteria to minimize the damage from the noises, the regulation only involves a weighted sound level (dB(A)), which is loudness, like other types of noises. It is therefore necessary to make typology of construction noise sources and evaluation vocabularies with the objective of making criteria for regulating construction noises suitable for the South Korean situation. While research based on a survey has been conducted to make typology of construction noise sources and evaluation vocabularies, there have been lots of difficulties in using it to make criteria for regulation because no consideration was given to psychological responses of people. On the basis of the findings from literature review, this study aimed to make typology of construction noise sources and vocabularies through a psycho-acoustic experiment and analyze the psychological characteristics and meanings of construction noises more accurately. The respondents’ psychological responses to construction noise sources were grouped into three factors ‘normal, shocking, and fluctuating noises’ and into ― ― six factors ‘annoying,’ ‘loud,’ ‘confusing,’ ‘noisy,’ ‘alarming,’ and ‘boisterous’ in terms of evaluation ― ― vocabularies. Since the factor with the biggest eigenvalue drawn from the respondents’ psychological responses is most important, the most important influential factor in evaluating construction noises was ‘normal noises’ for construction noise sources and ‘annoyance’ for evaluation vocabularies. This typology is expected to be useful to make and revise criteria for regulating construction noises.

In advanced countries, various policies are being enforced to reduce equipment noise level at it’s source. This paper analyses the problems of domestic noise policies related to noisy equipment, and presents a plan for improving the implementation of expansion policy of low noise equipment based on this analysis. This paper proposes that the equipment satisfying the compulsory rule be able to use the environmental certification mark, the standards of which are defined in recommended rules, to improve the linkage between the two policy measures. This paper also suggests expanding the range of equipment to be supervised and using new noise label that has grades and shows detailed noise level of the equipment to improve environmental certification system. In addition, supplementing the construction permission system and supporting international certification system are offered to expand the use of low noise equipment.

The object of this paper is to estimation of noise reduction effect of road noise by operating condition due to tire noise regulation. A prepare the countermeasure of the noise reduction according to collect tire/road noise data under various influencing factors by using the tire test method. To accomplish the object : A automotive is used as a test platform to test tire/road noise by changing different types of tires and using the On-Board Sound Intensity test system. The influence of inflation pressure, road, load, speed and pattern type on tire/road noise is compared and analyzed. At the same time, the mechanism of tire/road noise is analyzed, which provides an experimental basis for tire noise reduction.

PURPOSES: This paper presents the noise reduction effect of asphalt concrete pavement using steel slag aggregate. METHODS: Steel slag aggregates induce various mechanical effects because of their high stiffness and specific gravity. It is also known that the noise reduction effect is due to its high specific gravity and porous nature. In this study, the noise reduction in a steel slag asphalt concrete pavement section was measured and analyzed. RESULTS : On average, an asphalt concrete pavement with steel slag reduces road traffic noise by about 2 dB(A). In addition, the analysis of sound pressure levels by frequency showed lower sound pressure levels in steel slag asphalt concrete pavement than general HMA in all frequency ranges (from low to high frequencies). An analysis of the benefits with regard to noise, by assuming a road-traffic noise reduction of 2 dB(A) with asphalt concrete pavement using steel slag, shows that the noise abatement cost approach can save 1.6 million won a year over soundproof wall costs. In addition, the noise damage cost approach results in cost savings (with regard to noise) of between 19 and 60 million won per year depending on the population density. CONCLUSIONS: The use of steel slag aggregate as an asphalt concrete mixture material not only improves the mechanical performance but also has a noise reduction effect. It is expected that the steel slag asphalt concrete pavement can reduce the environmental burden by utilizing resources and provide a safer and more comfortable pavement condition to the road users.

By analyzing the status of Korean tire labeling regulation and comparing the performance indicators of tire labeling in different countries, this paper expounds the serious impact of tire noise on traffic noise pollution, and puts forward that in order to improve the comfort of car ride, control traffic noise pollution and build a green tire industry, the tire labeling system should be improved, and the corresponding requirements for tire rolling noise should be put forward according to the road conditions in Korea.

The study on the tire noise due to the On-Board Sound Intensity test method. The object of this project is to prepare the countermeasure of the noise reduction according to collect tire/road noise data under various influencing factors by using On-Board Sound Intensity test method. To accomplish the object ; A automotive is used as a test platform to test tire/road noise by changing different types of tires and using On-Board Sound Intensity test system. The influence of inflation pressure, road, load, speed and pattern type on tire/road noise is compared and analyzed. At the same time, the mechanism of tire/road noise is analyzed, which provides a experimental basis for tire noise reduction.

PURPOSES : Exposed aggregate concrete pavements have been adopted in several countries because of their advantages of pavement texture characteristics, which can produce low tire-pavement noise and higher load-carrying capacities. The magnitude of tire-pavement noise greatly depends on the wavelength of pavement texture. The wavelength of exposed aggregate concrete pavement can be controlled with maximum sizing and by controlling the amount of coarse aggregates in the concrete mixture. In this study, the maximum size and the amount of coarse aggregate in the exposed aggregate concrete pavement are investigated to produce equal levels of wavelength in the asphalt pavement. METHODS: A simple method to measure the average wavelength of pavement texture is introduced. Subsequently, the average wavelength of typical asphalt pavement is investigated. A set of mixture designs of exposed aggregate concrete with three maximum-sized coarse aggregates, and three amounts of coarse aggregate are used. The average wavelengths are measured to find the mixture design needed to produce equal levels of wavelength as typical asphalt pavement. RESULTS : With a cement content of 420 kg/m3 and fine aggregate modulus of 30%, the number of exposed aggregates was 48, and the shortest texture depth provided a wavelength of 4.2 mm. According to the number of exposed aggregates, the exposed aggregate concrete pavement could be rendered low-noise, because its wavelength was similar to that of asphalt pavement ranging from 3.9 to 4.4 mm. CONCLUSIONS : Selection of appropriate maximum sizes and the amount of coarse aggregates for exposed aggregate concrete pavement can produce a wavelength texture closely resembling that of asphalt pavement. Therefore, the noise level of exposed aggregate concrete pavement can be reduced with an appropriate maximum size and the amount of coarse aggregates are employed.

잠수함에서 발생하는 수중방사소음은 적함의 소나에 의해 피탐될 확률과 직결되며, 잠수함 저소음화 방안은 생존성 향상을 위해 필수적이다. 최신 잠수함의 경우 기계류 소음저감 및 고속/대형화가 진행됨에 따라 선체 주위에 발생하는 유동소음에 대한 관심이 높아지고 있다. 본 연구에서는 자유수면의 효과를 고려하여 잠수함 형상 주위에 발생하는 유동소음 수준을 예측할 수 있는 소음해석기법을 개발하였다. 잠수함이 자유수면 근처 운항시에 잠수함 주위 유동장의 교란에 의해 발생하는 난류유동소음과 쇄파버블에 의한 소음이 발생한다. 먼저 잠수함 주위 유동장 해석을 위해, VOF법 기반의 비압축성 이상유동(two-phase flow)해석을 수행하여 잠수함 주위 자유수면 형상과 유동장 정보를 도출하였다. 이후 난류유동소음해석을 위해 음향상사기법인 Permeable FW-H를 적용하였고, 쇄파버블 소음해석을 위해 유동해석에서 도출된 난류운동에너지 분포결과를 기반으로 쇄파버블 소음모델을 적용하였다. 최종적으로 개발된 유동소음 해석기법은 선박해양플랜트연구소(KRISO)의 대형캐비테이션터널(LCT)에서 수행된 잠수함 모형 유동소음계측 실험결과와 비교를 통해 검증을 수행하였다.

PURPOSES : In Korea, concrete pavements with transverse tining, which have excellent skid resistance, have been mainly constructed to secure road bearing capacity and safety. However, transverse tining has higher noise level of approximately 4-5 dB(A) compared with asphalt pavement. As a method to determine low-noise characteristics of concrete pavements, the fine-size exposed aggregate concrete pavement (EACP) has been studied in Korea and abroad. The surface of EACPs consists of exposed coarse aggregates and 2-3 mm removal surface mortar. EACPs have the advantages of maintaining low-noise and adequate skid-resistance levels during the performance period. Although EACPs have been widely studied to reduce noise, quantitative noise analysis with various paving methods has not been performed owing to differences in mixture proportioning, construction conditions, environmental conditions, and measurement methods. Therefore, the purpose of this study is to investigate the low-noise characteristics of fine-size EACPs by comparing noise with various paving methods, including concrete and asphalt pavements. METHODS: In this study, noise data were collected to quantitatively analyze the low-noise characteristics of EACPs compared with various paving methods such as transverse tining, longitudinal tining, SMA, and HMA. RESULTS: The evaluation of the low-noise characteristics of EACPs compared with transverse tining showed that the relative noise of 13 mm EACP with transverse tining was reduced by approximately 2% at 60 km/h, 4% at 80 km/h, and 5% at 100 km/h. The relative noise of 10 mm EACP with transverse tining was reduced to 3%, 7%, and 8% at 50 km/h, 80 km/h, and 100 km/h, respectively. In addition, it was confirmed that the noise of 10 mm EACP was similar to that of asphalt pavement. CONCLUSIONS : It was confirmed that EACP using 10 mm coarse aggregates generates lower noise than that using 13 mm coarse aggregates. Therefore, the use of coarse aggregates smaller than 10 mm needs to be considered to improve the low-noise effect of EACP.