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

Search Result 58, Processing Time 0.027 seconds

A Study on the Development of a New Muffler Component required in the Geometrically Constrained Space (제한된 공간에 맞는 새로운 소음기부품의 개발에 대한 연구)

  • 이정권;이병호
    • The Journal of the Acoustical Society of Korea
    • /
    • v.1 no.1
    • /
    • pp.76-81
    • /
    • 1982
  • To get minimum noise level by making full use of the constrained geometric space and being compatible with the minimum pressure-drop condition, 3-pipe through-flow system is designed by inserting a new pipe which is shaped a resonator in the cavity of 2-pipe system. As a result of the 1/3-octave-band frequency analysis for the noise reduction characteristics, this system is proved to have good sound attenuation effect in the high frequency region, so that it is found to be a useful component of a muffler.

  • PDF

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

  • Jung, Sung-Soo;Lee, Woo-Seop;Jho, Moon-Jae;Suh, Sang-Joon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2000.06a
    • /
    • pp.185-190
    • /
    • 2000
  • The sound absorption coefficient of glass wool (bulk density of 48 kg/$m^3$ and 32 kg/$m^3$) 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, 1/3-octave band and white noise, gives similar values.

  • PDF

An Investigation of Power Flow Mechanism in Beam-plate Built-up Structures with an Energy-absorbing Plate (보-판 결합 구조물에서 에너지 흡수체로 작용하는 판의 특성에 따른 파워 전달 특성에 관한 연구)

  • Yoo, Ji-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.17 no.1 s.118
    • /
    • pp.55-64
    • /
    • 2007
  • In the built-up structure consisting of a stiff beam and a flexible plate, Grice showed that the plate behaves as an energy absorber in narrow frequency bands(called plate blocking effect). This paper deals with such beam-plate coupled structures, where the plate is an energy absorber and the excited beam is an energy path. It is found that such energy dissipation can occur in the relatively broad bands, if different stiffnesses are used in the rectangular plate. It was experimentally verified by Heckl that the energies in terms of one-third octave band averages transferred to the plate(or dissipated in the plate) increase for increased plate damping. This Paper, however, shows that the energy absorption suddenly reduces at the certain narrow frequency bands where the plate damping effect upon the coupled beam is maximum. Also, in order to minimize energy transfer through the beam in terms of one-third octave band averages, it is advantageous to increase the plate damping closer to the excitation point All these results are based on the wane method.

The Study of Improvement of the Void Slab Applying the Impedance Method (임피던스법을 이용한 보이드 슬라브의 개선방안에 관한 연구)

  • 오재응;김영식
    • Journal of KSNVE
    • /
    • v.11 no.2
    • /
    • pp.276-284
    • /
    • 2001
  • In apartment buildings, floor-impact sound has been regarded as the major source that causes complaints from residents. It is mainly due to the use of light-weight structures and the lack of researches in terms of floor-impact sound. The purposes of this study are analyzing the characteristics of vibration response and sound radiation of 12type void slabs in the improvements void slab by impedance method and finding the fittest improvements void slab on the 12type void slab. The main results of this study are summarized as below: (1) In the $\frac{1}{3}$ octave band level of sound radiation, $\frac{1}{3}$ octave band levels, measured from four-divided improvement void slab(No.8) and eight-divided improvement void slab(No.12), are 10~25 dB lower than that of standard void slab(No.1) in the 1250 Hz. Especially, eight-divided improvement void slab(No.12) is the best void slab in terms of radiation efficiency of sound level. (2) In the correlation relation of acceleration and sound radiation, standard void slab(No.1), four-divided improvement void slab(No.8), SK standard four-hole void slab(No.10), and eight-divided improvement void slab(No.12) are positive correlation relation.

  • PDF

An analysis of railway noise from comparison and evaluation between A-weighted SPL and sound quality indices (A-weighted 음압레벨과 음질 지수의 평가 및 비교를 통한 철도소음의 해석)

  • Kim, Dae-Sung;Wang, Se-Myung;Shin, Min-Cheol;Cho, Jun-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2006.05a
    • /
    • pp.1459-1464
    • /
    • 2006
  • In the previous studies on railway noise analysis, the main purpose of noise analysis is concerned with the reduction of A-weighted sound pressure level in order to satisfy noise regulations. However, more important facts on noise reduction are the subjective feelings of the human being on noise because people might be annoyed from the noise caused by train. In this paper, railway noise from different type of train are compared using the calculation of sound quality metrics with using strength related method that is calculation of A-weighted sound pressure level.

  • PDF

Transfer Function of Structure-borne Noise to Underwater Radiated Noise (고체음의 수중방사소음 전달함수)

  • 김재승;김현실;김상렬
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2001.05a
    • /
    • pp.138-142
    • /
    • 2001
  • A comparison between theoretical and measured transfer function, which relates structure-borne noise source level to underwater radiated noise, of a naval ship is presented in this study. Transfer functions are obtained by dividing far field underwater noise by the value of structure borne noise source levels below machinery mounts. In prediction, statistical energy analysis of the whole ship structure is used to get vibration levels of wetted hull plates below water line. Then, far field radiated noise is calculated by summing up contributions from each plates using vibration levels and radiation efficiencies. And 1/3-octave band underwater sound pressure at the distance of 1 m away from the hull were measured to get experimental transfer functions. The two transfer functions are compared to show resonable agreements in spite of the subtle physical differences between each other.

  • PDF

Investigation into influence of sound absorption block on interior noise of high speed train in tunnel (터널 내부 도상 블록형 흡음재의 고속철도차량 내부 소음에 미치는 영향에 대한 고찰)

  • Lee, Sang-heon;Cheong, Cheolung;Lee, Song-June;Kim, Jae-Hwan;Son, Dong-Gi;Sim, Gyu-Cheol
    • The Journal of the Acoustical Society of Korea
    • /
    • v.37 no.4
    • /
    • pp.223-231
    • /
    • 2018
  • Recently, due to various environmental problems, blast tracks in tunnel are replaced with concrete tracks, but they have more adverse effects on noise than blast tracks so that additional noise measures are needed. Among these measures, sound-absorbing blocks start to be used due to its easy and quick installation. However, the performance of sound absorption blocks need to be verified under real environmental and operational conditions. In this paper, interior noise levels in KTX train cruising in Dalseong tunnel are measured before and after the installation of sound-absorbing blocks and the measured data are analyzed and compared. Additionally, noise reduction are estimated by modeling the high speed train, the tunnel and absorption blocks. Measurement devices and methods are used according to ISO 3381 and the equivalent sound pressure levels during the cruising time inside the tunnel are computed. In addition to overall SPLs(Sound Pressure Levels), 1/3-octave-band levels are also analyzed to account for the frequency characteristics of sound absorption and equipment noise in a cabin. In addition, to consider the effects of train cruising speeds and environmental conditions on the measurements, the measured data are corrected by using those measured during the train-passing through the tunnels located before and behind the Dalseong tunnel. Analysis of measured results showed that the maximum noise reduction of 6.8 dB (A) can be achieved for the local region where the sound-absorbing blocks are installed. Finally, through the comparison of predicted 1/3-octave band SPLs for the KTX interior noise with the measurements, the understanding of noise reduction mechanism due to sound-absorbing blocks is enhanced.

A Study on the Development of a Resonator to Reduce the Ship Engine Room Noise (선박기관실의 소음 저감을 위한 차폐공명기의 개발에 관한 연구)

  • Yu, Y.H.
    • Journal of Power System Engineering
    • /
    • v.11 no.4
    • /
    • pp.72-77
    • /
    • 2007
  • It is known that elimination of ship engine room noise is impossible thing, so the working environment in the engine room is getting worse because ships are recently built with huge engines to take higher sailing power. In the yacht and cruise yacht, the engine room noise is more serious because they have bigger engines relative to their hull sizes. The noise generated from the main engine makes the employee to hearing loss and the transmitted noise make the uncomfortable conditions in the cabins of ship. The noise generated by ship engine must be attenuate for the employee and passenger. In yacht and cruise yacht, the noise levels in cabines are the most important criterions to the value of commodities. In this study, the noise absorbtion barrier which have resonators is experimentally studied by the 1/3 octave band noise elimination rates(%).

  • PDF

Prediction of Non-cavitation Noise from Large Scale Marine Propeller (수치해석을 통한 대형 선박용 프로펠러의 비공동소음 예측)

  • Ryu, Ki-Wahn;Lee, Jong-Yeol;Kim, Bong-Ki;Byun, Jeong-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.25 no.2
    • /
    • pp.75-82
    • /
    • 2015
  • Noises from the large scale marine propeller are calculated numerically on non-cavitation condition. The hydrodynamic analysis is carried out by potential based panel method with time marching free wake approach. The distribution of hydrodynamic loads on the propeller surface and noise signals are obtained using the unsteady Bernoulli's equation and the Farasssat's formula respectively. It turns out that the noise signal at the narrow band shows strong peak at the blade passage frequency, and the peak value at the 1/3 octave band also shows the same trend. Noise signals and directivity patterns for both the thickness and the loading noise are compared with each other. The directivity pattern for the loading noise shows minor lobe at the backward side of the rotating disc plane.

Analysis of Vehicle Noise Effect by Microphone Position and Road Geometry (도로 기하구조에 따른 차량 Microphone 위치별 소음 영향 분석)

  • Moon, Hak Ryong;Han, Dae Cheol;Kang, Won Pyoung
    • International Journal of Highway Engineering
    • /
    • v.15 no.4
    • /
    • pp.75-83
    • /
    • 2013
  • PURPOSES: The purpose of study is to understand the characteristic of driving noise from the front and rear tire for effective active noise cancellation application. METHODS : As literature review, noise measurement methods were reviewed. Noise measurement conducted at three kind of section by road slope using CPX(Close Proximity Method). Noise data was compared by total sound pressure level and 1/3 octave band frequency sound pressure level. Also, each section was compared by T-test using SPSS. RESULTS : In the case of the uphill section, it was shown that the sound pressure level of the front tire at Sugwang-Ri and Sinchon-RI sections was higher than that of the rear tire in low and high frequency band. In the case of high slope section of Sangsaek-Ri, the sound pressure level of the front tire was higher than that of the rear tire in high frequency. Also, in the case of the downhill section, it was shown that the sound pressure level of the front tire at Sugwang-Ri and Sinchon-RI sections was higher than that of the rear tire in low frequency band. However, the sound pressure levels of both the front and rear tires were approximately the same in the high slope section of Sangsaek-Ri. The result of T-test showed that total sound pressures of the front and rear tires were not different from each other in the case of high slope and high speed. CONCLUSIONS: Road slope was not an important variable for effective active noise cancellation.