• Title/Summary/Keyword: 1/1 Octave Band Noise

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Real Time 1/3 Octave Band Control System for High Intensity Acoustic Chamber (음향 챔버 내부의 1/3 옥타브 스펙트럼 실시간 제어 시스템)

  • Kim, Young-Key;Kim, Hong-Bae;Moon, Sang-Mu;Woo, Sung-Hyun;Lee, Sang-Seol
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.881-885
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    • 2002
  • This paper presents the performance and the algorithm of a 1/3-octave band spectrum control system. The system is developed to provide various spectrums in a high intensity acoustic chamber. The required spectrum, which usually comes from launch vehicle company, starts from 25Hz band and ends 10kHz band. Automatic spectrum control system is preferred since the system requires short settling time to guarantee the safety of test objects and to reduce the amount of operating gas. The developed system adapted a PCI data-acquisition/signal-generation board installed in a personal computer to implement whole control logic. The control software used three cascade digital Butterworth filters using software. The filers are designed following ANSI S1.11 standard to implement 1/3 octave band filter bank. The graphical user interface of the system guides the user to follow standard operation procedure. The averaged control spectrum showed less than 0.05 dB in every running 1/3-octave band.

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Real-Time 1/3-Octave Band Spectrum Control System of High Intensity Acoustic Chamber (음향 첨버 내부의 1/3-옥타브밴드 스펙트럼 실시간 제어 시스템)

  • Kim, Youngkey K.;Kim, Hong-Bae;Moon, Sang-Mu;Woo, Sung-Hyun;Lee, Sang-Seol
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11a
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    • pp.386.2-386
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    • 2002
  • This paper reports the performance and the Algorithm of an 1/3-octave band spectrum control system. The system is developed to provide various required spectrums in a high intensity acoustic chamber. The required spectrums, which usually comes from launch vehicle specification, starts from 25㎐ band and ends 10,000㎐. Short settling time is required to guarantee the safety of test objects and reduce the amount of operating gas. (omitted)

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Field Test and Evaluation of Noise from Wind Turbine Generators at Yongdang and Hangwon in Jeju Island (제주도 용당/행원 풍력발전기 현장 소음 실증)

  • Cheong, Cheol-Ung;Jeong, Sung-Su;Cheung, Wan-Sup;Shin, Su-Hyun;Jeon, Se-Jong;Lee, Saeng-Hui
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.818-821
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    • 2005
  • The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from 1.5 MW wind turbine generator (WTG) at Yongdang and 660 kW WTG at Hangwon in Jeju Island. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. 1.5 MW WTG at Yongdang is found to emit lower sound power than 660 kW one at Hangwon, which seems to be due to lower rotating speed of the rotor of WTG at Yongdang. Equivalent continuous sound pressure levels (ECSPL) of 660 kW WTG at Hangwon vary more widely with wind speed than those of 1.5 MW WTG at Yongdang. The reason for this is believed to be the fixed blade rotating speed of WTG at Yongdang. One-third octave band analysis of the measured data show that the band components around 400-500 Hz are dominant for 1.5 MW WTG at Yongdang and those around 1K Hz are dominant for 660 kW WTG at Hangwon.

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Field Test and Evaluation of Wind Turbine Noise according to IEC Standards (IEC 규격에 따른 풍력 터빈 소음의 현장 실증)

  • Cheong, Cheol-Ung;Jung, Sung-Su;Cheung, Wan-Sup;Shin, Soo-Hyun;Chun, Se-Jong;Lee, Sang-Hee
    • 한국신재생에너지학회:학술대회논문집
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    • 2005.11a
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    • pp.579-582
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    • 2005
  • The sound measurement techniques in IEC 61400-11 are applied to field test and evaluation of noise emission from 1.5 MW wind turbine generator (WTG) at Yongdang-Lee and 650 kW WTG at Hangwon-Lee in Jeju Island. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. 1.5 MW WTG at Yongdang is found to emit lower sound power than 660 kW one at Hangwon, which seems to be due to lower rotating speed of the rotor of WTG at Yongdang. Equivalent continuous sound pressure level s (ECSPL) of 650 kW WTG at Hangwon vary more widely with speed than those of 1.5 MW WTG at Yongdang. The reason for this is believed to be the fixed blade-rotating speed of WTG at Yongdang. One-third octave band analysis of the measured data show that the band components around 400-500 Hz are dominant for 1.5 MW WTG at Yongdang and those around 1K Hz are dominant for 660 kW WTG at Hangwon.

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Wind Turbine Noise (풍력발전기 소음평가)

  • Jung, Sung Soo;Jeon, Byung Soo;Seo, Jae Gap;Lee, Yong Bong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.431-434
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    • 2014
  • Wind turbine industry is the most developing field among other renewable energy industry. As expanding wind farms, noise is the big problem to solve. This study is about wind turbine noise measuring method based on IEC 61400-11. Sound pressure levels, 1/3-octave band levels, and low frequency sound pressure levels of a 3 MW wind turbine were measured and analyzed.

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Noise Evaluation of the Rumble Strips Constructed at Tall Gate of Highway (고속도로 영업소 광장의 럼블스트립 관련 소음평가)

  • Lee, Jae-Jun;Mun, Sung-Ho;An, Deok-Soon;Kwon, Soo-Ahn
    • International Journal of Highway Engineering
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    • v.14 no.5
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    • pp.201-206
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    • 2012
  • PURPOSES: This study evaluated a measuring technique for tire-pavement interaction noise that uses a noble close proximity (NCPX) method as well as for noise level measured inside of a car (e.g., Inside Noise Level) in term of rumble strips constructed at a tall gate. METHODS: According to the measurements of NCPX and inside noise level (INL), 1/3 octave band frequency analysis and overall noise level calculation were conducted in order to evaluate noise levels of NCPX and INL, depending on types of rumble strips. RESULTS: The tested sections of general concrete pavement surface and two different types of rumble strips were evaluated, using 1/3 octave band frequency analysis and overall noise level. From the analyzed results, it can be concluded that rumble strips generate a relatively huge noise levels when compared to the concrete pavement surface. CONCLUSIONS: Noting that above 3 dBA different noise levels can let drivers know that they are getting close to toll gate; therefore, they should apply their brakes. Thus, the noise levels of rumble strips are required to be reduced, based on considering the neighbors living near toll gates.

A Study for Comparing Road Noise by Surface Types using NCPX (NCPX를 이용한 도로 표층 유형별 노면 소음 비교 연구)

  • Kang, Won Pyoung;Moon, Hak Ryong
    • International Journal of Highway Engineering
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    • v.15 no.6
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    • pp.61-68
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    • 2013
  • PURPOSES : The purpose of this study is to study the noise reducing effect of Micro Surfacing by comparing general asphalt, longitudinal tining and Slurry Seal. METHODS : This study measures vehicles' noise of each section by the NCPX method that can measure noise between the road surface and the tire at the field. Total sound pressure and sound pressure level by the 1/3 octave band frequency are calculated through the field data of each section. Total sound pressure level is compared by ANOVA test statistically. After ANOVA test, post-hoc test is conducted to know mean difference of surface type by Tukey. RESULTS : As the result of CPB analysis to confirm sound pressure levels by frequency, it was shown that sound pressure levels by frequency are totally similar except for those of frequency bands between 100Hz and 500Hz. The result of ANOVA test and post-hoc test, it was shown that sections of surface type have a difference. The result of Micro Surfacing was lower 2~5dB(A) than other surface type. CONCLUSIONS : It is found that the noise reduction performance of Micro Surfacing was better than other surface type.

Characteristic of Road Traffic Noise According to Road Vertical Alignment (도로 종단선형에 따른 도로교통 소음 특성 분석)

  • Moon, Hak Ryong;Han, Dae Cheol;Kang, Won Pyoung
    • International Journal of Highway Engineering
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    • v.15 no.4
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    • pp.95-105
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    • 2013
  • PURPOSES: The purpose of this study is to research the influence of road traffic noise by road slope through the analysis of the field road traffic noise and determine consideration of road slope in the case of appling active noise cancellation. METHODS: This study measures vehicle's noise by the NCPX method at the three field sections such as uphill, downhill, and flatland. Total sound pressure and sound pressure level by the 1/3 octave band frequency are calculated through the raw field data. Total sound pressure level is compared by ANOVA test and T test statistically. The results obtained are compared in accordance with the road slope and the progress of the uphill section. RESULTS : The noise characteristic of early, medium, and last parts of uphill was found to be consistent when the vehicle was travelling uphill section. The result of statistical test, it was shown that total sound pressures are not different each other. According to the comparison by the geometry, sound pressure of the uphill section was higher than those of the flatland and downhill section in high frequency band. By the result of statistical test, total sound pressure are different according to geometry in the case of high vehicle speed. In the comparison result by road slope, each sound pressure level was found to be consistent in total frequency. However, total sound pressure proportionally increased according to road slope. CONCLUSIONS: It is found that the effect of road slope on noise generation was little in this experimental sites.

A Study on the Sound Absorption Coefficient by Varying Sample Size (시편의 크기에 따른 흡음계수 변화 연구)

  • 정성수;이우섭;조문재;서상준
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.5
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    • pp.83-88
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    • 2001
  • The sound absorption coefficient of glass wool (bulk density of 48 kg/m:1 and 32 kg/m7) was measured by reverberation room method as varying their cross-sectional area. The results show that the absorption is larger for smaller samples because of edge effect. The absorption coefficient with two different kinds of sources. 1/.7-octave band and while noise, gives similar values.

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An Experimental Study on the Propagation of Impulse Noise in the Far Sound Field (원음장에서의 충격성 소음전파에 관한 실험적 연구)

  • 송화영;제현수;이주원;이성태;이동훈
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.852-855
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    • 2004
  • This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a straight pipe attached to the open end of a simple shock tube. The sound pressure level and directivity of the impulse noise propagating from the exit of pipe with several different diameters are measured in the far sound fold for the range of the incident shock wave Mach number between 1.07 and 1.26. The experimental results showed that the peak values of impulse noises had a strong dependance on the exit diameter of a pipe and the shock wave Mach number. The impulse noise had the directivity propagating toward to the pipe axis and the characteristics of inverse square law of propagation distance. Moreover, it was shown that the one-third octave band SPL of impulse noise was almost constant regardless of the frequency band.

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