Experimental Identication of Acoustic Emission Characteristics of Large Wind Turbines with Emphasis on Infrasound and Low-Frequency Noise

정성수,정완섭,Cheolung Cheong,신수현 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

Infrasound and low-frequency noise below 200 Hz is known to affect the health of human beings. The main purpose of this paper is to experimentaly identify the characteristics of acoustic emission of large modern upwind wind turbines with emphasis on infrasound and low-frequency noise. The sound measurement procedures of IEC 61400-11 and ISO 7196 are applied to field test and noise emission from each of 1.5-MW and 660-kW wind turbines utilizing the stal regulation and the pitch control for power regulation is evaluated. The sound spectral density showed that the blade-passing-frequency (BPF) noise is clearly dominant up to 6 - 7 harmonics, which generaly occupy the frequency range of 1 - 10 Hz, i.e., infrasound. The A-weighted sound pressure levels (SPLs) of the stal control type of wind turbine were found to increase with wind speed in a more correlated way than those of the pitch control type of wind turbine while the G-weighted SPLs of low-frequency noise, including infrasound, were found to show a positive correlation with the wind speed irrespective of the method of power regulation. Potential complaints of local communities about infrasound and low-frequency noise of wind turbines are assessed by comparing the measured data with the existing hearing thresholds and criteria curves. These comparisons show that it is highly possible that low-frequency noise from the 1.5-MW and the 660-kW wind turbines in the frequency range over 30 Hz may lead to psychological complaints by ordinary adults and that in- frasound in the frequency range from 5 Hz to 8 Hz could cause complaints due to rattling house fittings such as doors and windows.

소리전달경로를 고려한 풍력발전기 소음 소리성분 연구

김봉영(Bong-Young Kim),송욱진(Uk-Jin Song),배명진(Myung-Jin Bae) 인문사회과학기술융합학회 2018 예술인문사회융합멀티미디어논문지 Vol.8 No.10

급격한 산업발달은 화학에너지를 고갈시키고, 지구온난화를 심화시키고 있다. 풍력발전기는 자연친화적인 신재생에너지로써 주목을 받고 있다. 그러나 풍력발전기의 가동시 발생하는 소음으로 인해 인근 주민들의 민원이 끊이지 않고 있다. 풍력발전기 소음은 일반 생활소음과 다르게 매우 낮은 저주파 소음과 충격소음의 특성을 가지고 있다. 그러나 풍력발전기 소음에 대한 허용기준조차 없이 일반 환경소음 기준만을 적용하고 있는 실정이다.본 논문에서는 소리전달경로를 고려하여 풍력발전기 소음이 어떠한 특성으로 전파되는지 확인하였다. 실험결과 일반 생활소음이 800m를 전파하여 측정위치보다 소음레벨이 32dB가 감소하였던 반면, 풍력발전기 소음은 2000m를 전파해야 측정위치보다 소음레벨이 32dB 감소하는 것을 확인하였다. 또한, 풍력발전기 소음은 저주파성분의 충격소음도 함께 멀리까지 전파되었으며, 저주파성분만 집중적으로 남아 전파함으로써 매우 답답함을 느끼게 하는 것을 확인하였다 Rapid industrial development is depleting chemical energy and deepening global warming. The wind power plant is attracting attention as a nature-friendly renewable energy. However, due to the noise generated during the operation of the wind power plant, the complaints of nearby residents are still continuing. The noise of the wind power plant is characterized by very low low-frequency noise and impact noise, unlike ordinary living noise. However, there is no acceptance criterion for wind power plant noise. Only the general environmental noise standard is applied to wind power plant. In this paper, the characteristics of wind power plant noise are analyzed by considering the sound propagation pathways. Experimental results show that the noise level is reduced by 32dB from the measured position when the ordinary living noise propagates 800m. On the other hand, it is confirmed that the noise level is reduced by 32dB from the measured position when the wind power plant noise propagates at 2000m. In addition, the noise of the wind power plant propagated far away along with the impact noise of the low frequency components, and it was found that only the low frequency components were intensively remained so that the wind power plant noise was very uncomfortable.

버스의 저주파 소음 분석

정성수,전병수,서재갑,김용태 한국물리학회 2009 새물리 Vol.59 No.5

Low-frequency noise below 250 Hz, including infrasound (< 20 Hz), is known to affect the human circulatory, respiratory, nervous, and endocrine systems. In the middle of the 1990's, some European countries prepared guidelines to measure and evaluate the low-frequency noise. We, however, are still in the initial stage of doing so. In this article, low-frequency noise levels of buses were investigated. The results indicated that the interior peak noise level was almost 100 dB at 12.5 and 16 Hz. The peak noise frequencies could be well explained by the first resonance of the inner space of the bus. The noise level of the bus in the frequency range between 12.5 and 50 Hz may lead to an oppressive and vibration feeling. Therefore, further research on the reduction of low-frequency noise is required for a quieter mass-transportation environment. 저주파 소음은 비록 귀에는 잘 들리지 않으나 장시간 노출될 경우 사람의 순환계, 호흡계, 신경계 그리고 내분비계 등에 영향을 주는 것으로 알려져 있다. 따라서 이미 몇몇 유럽국가들은 1990년 중반에 저주파 소음에 대한 측정 및 평가방법에 대한 지침서를 마련한 바 있으나 국내의 연구는 아직 초기단계에 있다. 본 연구에서는 대중교통 수단인 버스를 대상으로 버스 내 저주파 소음이 어느정도 발생되고 있는지를 살펴보았다. 측정결과 12.5와 16 Hz에서 100 dB 정도의 강한 피크 소음이 발생되었으며, 이것은 버스의 내부 공간에 대한 음향 공명 주파수에 해당됨을 알 수 있었다. 주파수 12.5 ~ 50 Hz 범위에서는 인체에 압박감과 진동감을 줄 수 있을 정도의 소음이 발생되므로 향후 저주파 소음 저감 대책에 대한 연구가 요구된다.

차량용 브레이크 시스템의 Low Frequency Noise 해석 연구

조호준(Hojoon Cho),이재한(Jaehan Lee),이종화(Jongwha Lee),정명구(Myoungkoo Chung),오정용(Jungyong Oh),장진희(Jinhee Jang),김인동(Indong Kim) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5

Brake low frequency noise phenomena (Moan, Groan Noise) are occurred by frictional stick-slip between pads and a rotor. When frictional stick-slip between pads and a rotor is occurred, this excitation source makes resonance of suspension system, which can generate structure-borne noise. Therefore, mechanism of low frequency noise phenomena should be systematically approached and analyzed in many different directions. In this study, automotive brake low frequency noise phenomena were approached and analyzed through three different simulation methods. A complex Eigenvalue analysis, steady state dynamic analysis and dynamic explicit analysis were performed and compared in an automotive drum brake system of trailing arm suspension type. For this, modal testing in the state of vehicle was performed and correlated with finite element analysis. Drum brake system was used in brake squeal noise simulation FE model which were correlated with brake components and sub-assembly modal testing results. Finally, causes of low frequency noise phenomena in this brake system were analyzed through three simulation methods.

Current–voltage and low-frequency noise analysis of heterojunction diodes with various passivation layers

Ko, Young-Uk,Yun, Ho-Jin,Jeong, Kwang-Seok,Kim, Yu-Mi,Yang, Seung-Dong,Kim, Seong-Hyeon,Kim, Jin-Sup,An, Jin-Un,Lee, Hi-Deok,Lee, Ga-Won Elsevier 2016 THIN SOLID FILMS - Vol.598 No.-

<P><B>Abstract</B></P> <P>Low-frequency noise (1/<I>f</I> noise) has been analyzed to characterize the amorphous/crystalline silicon heterojunction diodes with passivation layer of a-Si:H (p–i–n), Al<SUB>2</SUB>O<SUB>3</SUB> (p–Al<SUB>2</SUB>O<SUB>3</SUB>–n), and ZnO (p–ZnO–n) and without passivation (p–n). Four types of diodes show high ideality factors and the dependence of the reverse leakage current on the electric field shows that the diodes commonly follow the Poole–Frenkel model, which is field-assisted thermionic emission from the traps in the materials. However, the conduction mechanism in the reverse bias can be more easily clarified from the bias dependence of the 1/<I>f</I> noise. That is, the p–i–n and p–n diodes are affected by the diffusion current mechanism, and the p–Al<SUB>2</SUB>O<SUB>3</SUB>–n and p–ZnO–n diodes with an inferior interface are affected by the generation–recombination current mechanism. This indicates that the p–i–n and p–n diodes have a better interface quality than the p–Al<SUB>2</SUB>O<SUB>3</SUB>–n and the p–ZnO–n. These results show that the 1/<I>f</I> noise measurement can be a useful and more sensitive method to estimate the interface quality of heterojunction diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Leakage current is on Poole–Frenkel in heterojunction diode with inferior interface. </LI> <LI> Low-frequency noise is proposed to evaluate heterojunction diode. </LI> <LI> Low-frequency noise is useful to distinguish the leakage conduction mechanism. </LI> </UL> </P>

Analysis of sound absorption performance of an electroacoustic absorber using a vented enclosure

Cho, Youngeun,Wang, Semyung,Hyun, Jaeyub,Oh, Seungjae,Goo, Seongyeol Elsevier 2018 Journal of sound and vibration Vol.417 No.-

<P><B>Abstract</B></P> <P>The sound absorption performance of an electroacoustic absorber (EA) is primarily influenced by the dynamic characteristics of the loudspeaker that acts as the actuator of the EA system. Therefore, the sound absorption performance of the EA is maximum at the resonance frequency of the loudspeaker and tends to degrade in the low-frequency and high-frequency bands based on this resonance frequency. In this study, to adjust the sound absorption performance of the EA system in the low-frequency band of approximately 20–80 Hz, an EA system using a vented enclosure that has previously been used to enhance the radiating sound pressure of a loudspeaker in the low-frequency band, is proposed. To verify the usefulness of the proposed system, two acoustic environments are considered. In the first acoustic environment, the vent of the vented enclosure is connected to an external sound field that is distinct from the sound field coupled to the EA. In this case, the acoustic effect of the vented enclosure on the performance of the EA is analyzed through an analytical approach using dynamic equations and an impedance-based equivalent circuit. Then, it is verified through numerical and experimental approaches. Next, in the second acoustic environment, the vent is connected to the same external sound field as the EA. In this case, the effect of the vented enclosure on the EA is investigated through an analytical approach and finally verified through a numerical approach. As a result, it is confirmed that the characteristics of the sound absorption performances of the proposed EA system using the vented enclosure in the two acoustic environments considered in this study are different from each other in the low-frequency band of approximately 20–80 Hz. Furthermore, several case studies on the change tendency of the performance of the EA using the vented enclosure according to the critical design factors or vent number for the vented enclosure are also investigated.</P> <P>In the future, even if the proposed EA system using a vented enclosure is extended to a large number of arrays required for 3D sound field control, it is expected to be an attractive solution that can contribute to an improvement in low-frequency noise reduction without causing economic and system complexity problems.</P>

국내 저주파수 무작위 지진잡음의 특성 연구

박이슬 ( Iseul Park ),김기영 ( Ki Young Kim ),변중무 ( Joong Moo Byun ) 한국지구물리·물리탐사학회 2016 지구물리와 물리탐사 Vol.19 No.2

To investigate spatial and temporal variations of low-frequency (≤ 5 Hz) ambient seismic noise, we analyzed the noise data recorded for one whole year of 2014 at surface accelerometer stations in South Korea. After decomposed into low-frequency (LF; < 1 Hz) and high-frequency (HF; ≥ 1 Hz) components, the root-mean-squared (RMS) amplitudes and power spectral densities (PSD) of the noise data were computed. The RMS amplitudes were larger on islands and near-shore stations, but also large RMS amplitudes were observed at inland stations in large cities only for HF components. The RMS amplitudes of HF components were larger in the daytime than at nighttime and during weekdays than on Sunday and holidays. This indicates the HF components are closely related to human activities. On the contrary, daily and weekly variations were not clear in the LF components while they showed seasonal variations with its maximum during the winter and a good correlation with significant wave height. Therefore, we interpret the mechanism of LF components is closely related to natural phenomena such as sea. The amplitude of LF components decreased as an exponential function of the distance to the center of typhoons. The exponential index of .0.76 suggested that ambient seismic noise included both surface and body waves. Peak frequencies of the PSD curves were near 0.34 Hz indicating the double frequency. No temporal variation in the peak frequency was clearly noticed.

풍력발전시설 소음 측정 방법에 대한 고찰

이영진,이종태,민현경,권선용,이병찬 한국환경영향평가학회 2023 환경영향평가 Vol.32 No.5

Recently, as wind farms using wind power as new and renewable energy have been installed nationwide, noise problems have emerged. The environmental impact assessment and postenvironmental impact assessment also require the measurement of background noise and lowfrequency noise for wind farms, especially by applying the living noise measurement method according to the low-frequency noise management guidelines issued by the Ministry of Environment in 2018. Due to the nature of wind power generators that generate loud noise in high winds, noise measurement should be made at high winds, but when wind speed increases, wind noise increases and living noise and low-frequency noise are not properly evaluated. Therefore, the type of noise generated by wind power generators was confirmed, and matters to be considered when measuring wind noise such as wind noise were confirmed.

풍력발전기 저주파 소음해소에 관한 연구

박상범,이원희,배명진 사단법인 인문사회과학기술융합학회 2017 예술인문사회융합멀티미디어논문지 Vol.7 No.9

The modernization of the upgrading system makes use of chemical energy indiscriminately and the global warming has become acute and serious, and by developing renewable energy sources that are environmentally friendly throughout the world, In JeJu Island, development is being carried out with an interest in renewable energy. In the case of renewable energy, wind power generators complain that the residents of the nearby houses are suffering because of the low frequency noises that come out when they are operated In this study, we propose a method to solve the low-frequency noise from the wind power generator.The results of the experiment show that the wind power generation facility During construction at sea, it was possible to obtain neutralization and masking effects due to sea and wind noise from the sea, and wind power generation facilities were built on the sea, and fishing grounds were formed for the com- plex structures It is proposed that rational measurement regulations capable of measuring low-frequency noise due to the activation of the wind power generation industry and noise environment standards that reflect this will be prepared. It is necessary to investigate the noise situation of the environment inhabited by the residents near the wind power generation facility. 산업이 근대화가 됨에 따라 화학에너지를 무분별하게 사용하여 지구 온난화가 급격히 심화되고 있다. 이로인해 전세계적으로 친환경적인 신재생에너지를 개발함에 따라, 국내에서도 신재생에너지에 관심을 갖고 개발을 하고 있다. 신재생에너지 중 풍력발전기는 가동될 때 나오는 저주파 소음 때문에 인근 주거주민들이 고통을 호소하고 있다. 이에따라, 최근 제주도에서 해상에 풍력발전시설을 건설을 하고 있다. 본 연구에서는 풍력발전기에서 나오는 저주파 소음을 해소방법을 제안하였다. 실험결과, 풍력발전시설을 해상에 건설 시, 바다에서 불어오는 해풍과 파도소리로 인해 중화 및 마스킹효과를 얻을 수 있었다. 또한, 풍력발전시설이 해상위에 건설되어 콘크리트 구조물로 인해 어장이 형성되는 이점이 있다. 풍력 발전산업이 활성화 됨에 따라 저주파소음을 측정할 수 있는 합리적인 측정 규제와 이를 반영한 소음 환경 기준이 마련될 것을 제안한다. 이 제안을 기준으로 풍력발전시설 인근 주민들이 주거하는 환경의 소음실태를 조사할 필요가 있다.

음향메타물질 기반 차음판넬의 유한요소 모델링

왕세명(Semyung Wang),정재순(Jaesoon Jung),현재엽(Jaeyub Hyun) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4

Noise insulation panels have been widely used to insulate the sound from the source to receiving region. Generally, the noise insulation performance of the panel is proportional to the product of mass and frequency of the noise source. This is known as mass law. Therefore the noise insulation panel is very weak to the low frequency noise. Although the noise insulation performance is proportional to the mass also, increasing mass should be avoided for many machines. To overcome this limitation, the acoustic metamaterial is proposed, recently. The acoustic metamaterial is a grid structure which composed of thick frame and thin plate. Using the anti-resonance effect, the acoustic metamaterial shows good noise insulation performance in low frequency region compared with flat panel with same mass. To design and investigate the noise insulation performance of acoustic metamaterial based panel, the effective analysis method should be established. Thus, this paper presents the finite element analysis procedure for acoustic metamaterial based noise insulation panel. The panel is discretized by 3node triangular element and the radiated sound is computed by assuming the panel as a set of elementary radiators. The computed transmission loss shows acoustic metamaterial is better compared with flat panel with the same mass.