• Title, Summary, Keyword: Sound characteristics

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A Simulation for the Characteristics of the Sound-Pipe of King Song-Dok Bell (시뮬레이션에 의한 성덕대왕 신종 음관의 특성)

  • Choi Myung-Jin;Park Hong-Eul
    • Journal of the Korea Society for Simulation
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    • v.14 no.4
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    • pp.69-76
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    • 2005
  • To investigate the characteristics of the sound-pipe on the top of King Song-Dok bell, using computer simulation, the throat impedance was evaluated for the straight pipe and conical pipes with varying taper angles. When sound propagates in a rigid walled, unflanged circular pipe with wavelength larger than radius, the acoustic motion is planar, much as in a bar. The incident sound waves are reflected at the end of pipe and some of them are transmitted. The reflection coefficient and radiation impedance of the sound-pipe of King Song-Dok bell were calculated, and the results demonstrated that the high frequency sound is radiated through the sound-pipe. It behaves like a frequency filter.

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Development and Application of Measuring Method for Instantaneous Intensity (순시 인텐시티 측정 기법의 개발 및 응용)

  • 이장우;안병하
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.960-963
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    • 2003
  • Sound intensity method is well known as a visualization technique of sound field and sound propagation in noise control. Sound intensity is a vector quantity that describes the magnitude and the direction of net flow of acoustic energy at a given position. The current measuring method is expensive and difficult to identify the noise source exactly. In this paper, we have studied the noise source identification and the characteristics of noise source of rotary compressor for air conditioner using complex sound intensity method. The new method for instantaneous sound intensity is also proposed and it is useful for transient state and steady state. The criteria of these state, select auto correlation coefficient. The advantage, simplicity and economic attribution of this method are verified by analyzing the characteristics of noise source with instantaneous sound intensity compared to mean sound intensity.

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Development and Application of Measuring Method of Instantaneous Intensity (순시 인텐시티 측정 기법의 개발 및 응용)

  • 이장우;김영종;안병하;이운섭
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.560-563
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    • 1997
  • Sound intensity method is well known as a visualization technique of sound field and sound propagation in noise control. Sound intensity is a vector quantity that describes the magnitude and the direction of net flow of acoustic energy at a given position. The current measuring method is expensive and difficult to identify the noise source exactly. In this paper, we have studied the noise source identification and the characteristics of noise source of rotary compressor for air conditioner using complex sound intensity method. The new method for instantaneous sound intensity is also proposed and it is useful for transient state and steady state. The criteria of these states select auto correlation coefficient. The advantage, simplicity and economic attribution of this method are verified by analyzing the characteristics of noise source with instantaneous sound intensity compared to mean sound intensity.

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Effects of the sound field characteristics of the receiving room on heavy-weight impact sound measurement generated by impact ball (임팩트 볼에 의한 중량충격음 측정에 있어서 수음실 음장특성의 영향)

  • Yoo, Seung-Yup;Lee, Sin-Young;Jeong, Young;Jeon, Jin-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.622-625
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    • 2006
  • This study is a fundamental investigation for standardization of the heavy-weight floor impact measuring method by the impact ball. The distribution chrematistics of floor impact sound level and reverberation time in a receiving room of the testing building for floor impact sound were measured with variations of number and arrangement of the sound-absorbing materials. Total 8 cases were investigated. The distribution of the floor impact sound level($L_{i,\;Fmax}$) was measured at 30 points with same intervals. The absorption coefficient of the room is 0.10 in case of installation of 6 absorbing materials and 0.02 in case of non-installation. The distribution shape of the impact sound pressure level was similar to the result of the bang machine driving at the measured frequency range. However, the overall reduction of the impact sound level investigated in the 125 to 500 Hz shows that the sound absorption characteristics of the receiving room actually affects the result of the heavy-weight impact measurement.

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Analysis of Heart Sound Using the Wavelet Transform (Wavelet Transform을 이용한 Heart Sound Analysis)

  • 위지영;김중규
    • Proceedings of the IEEK Conference
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    • pp.959-962
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    • 2000
  • A heart sound algorithm, which separates the heart sound signal into four parts; the first heart sound, the systolic period, the second heart sound, and the diastolic period has been developed. The algorithm uses discrete intensity envelopes of approximations of the wavelet transform analysis method to the phonocard-iogram(PCG)signal. Heart sound a highly nonstation-ary signal, so in the analysis of heart sound, it is important to study the frequency and time information. Further more, Wavelet Transform provides more features and characteristics of the PCG signal that will help physician to obtain qualitative and quantitative measurements of the heart sound.

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Absorption Characteristics of Sound Proof Wall by Scrap Aluminum and Perforated Plate (알루미늄칩과 타공판을 이용한 방음벽 충진재의 흡음특성)

  • Lee, Young-Jung;Kim, Dae-Gun;Park, Kyung-Hwa;Kim, Young-Do
    • Korean Journal of Materials Research
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    • v.19 no.7
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    • pp.382-385
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    • 2009
  • Efforts to reduce noise in industrial application fields, such as automobiles, aircrafts, and plants have been gaining considerable attention while a sound proof wall to protect people from the noise has been intensively investigated by many researchers. In this study, our research group suggested creating a new sound proof wall composed of scrap aluminum chips and perforated plates in a commercial polyester sound proof wall, which was then successfully fabricated. This wall's sound absorption characteristics were measured by an impedance tube method. The sound absorption property was evaluated by measuring the Noise Reduction Coefficient (NRC) to the standard, ASTM C 423-90a. The noise reduction coefficient of the sound proof wall composed of 3.5 vol.% and 7.5 vol.% of scrap aluminum chips relatively increased to 5% and 8% compared to the commercial polyester sound proof wall. The scrap aluminum perforated plate also relatively increased to 13% compared to the commercial polyester sound proof wall.

An Experimental Study on the Prediction of Indoor Sound Level Distribution in Apartment for Exterior Noise (외부소음에 대한 공동주택 실내 소음레벨분포에 관한 실험적 연구)

  • Park, Hyeon-Ku;Kim, Jong-Bin;Kang, Dong-Yong;Jang, Hyun-Choong;Song, Hyuk;Kim, Sun-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.259-264
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    • 2001
  • It is necessary to predict the sound pressure level(SPL) in rooms before designing an apartment when exterior noises are produced. In order to predict SPL for an apartment that has some specific exterior noises, the following should be known: the characteristics of outdoor noise, sound insulation performance and sound level differences of each room. The purpose of this study is to find out the possibility of predicting sound pressure level of rooms in an apartment by analysing sound level differences among rooms. Sound sources used in this experiment are construction noise, aircraft noise, railroad noise, road traffic noise and white noise as a reference to compare with the previous four. These noises were recorded and reproduced by speaker. As a result, we found that within the sound reduction pattern, the sound difference level appeared uniform depending on the sound insulation characteristics of the windows installed when facing the noise source. When the windows having the same acoustic performance were installed, the SPL in each room resulted in nearly the same values.

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A Study on the Reduction of the Lightweight Impact Sound Level by Floor Coverings (바닥마감재가 경량충격음 저감량 평가에 미치는 영향)

  • 정진연;이성호;정갑철
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.137-142
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    • 2004
  • The aim of this study is to investigate the characteristics and quantity of the noise reduction by floor coverings. The characteristics on the reduction of the lightweight impact sound level by floor coverings is as follows. The insulation level attained by floor coverings tends to be smaller in actual buildings than in public laboratories. The reduction of the impact sound level to the tape is similar to the method of adhesives. For this reason, the reduction of impact sound level by floor coverings in public laboratories can be utilized to tape. And the reduction of impact sound level by floor coverings is not influenced by the size of specimen except the specific frequency.

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An Evaluation on the Sound Insulation Performance of Drywall for High-Rise Buildings (초고층 건물에 적용 가능한 건식벽체의 차음성능 평가)

  • Lee, Sang-Woo;Yoo, Ho-Chun;Lee, Su-Yeal;Jung, Gap-Chul;Jung, Young-Min
    • KIEAE Journal
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    • v.7 no.2
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    • pp.3-8
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    • 2007
  • Recently, the structural system of public residential buildings has been changed from the reinforced concrete (RC) wall system to the (PC) wall and moment resisting systems. Thus, it is important to develop the suitable wall system in accordance with the trend of the modern structural system. This paper presents the basic study on the suitable boundary wall in high-rise buildings. The research also demonstrates the evaluation results on sound characteristics in the aspect of sound insulation. The evaluation of sound insulation capability for the commercialized wall structure was conducted based on literature survey while the measurement of sound insulation capability for the light-weght EPP concrete was performed in according to KS F2808 in laboratory. The main objective of this research is to propose the most suitable dry wall system as a sound insulation structure through the comparison and analysis of frequency characteristics and weight-acoustic attenuation.

A Study on Acoustical Characteristics in Microcellular Foaming Plastics (초미세 발포 플라스틱의 음향특성 연구)

  • Cha, Sung-Woon;Kim, Hak-Bin;Lee, Byoung-Hee;Kang, Yon-Jun
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.9
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    • pp.71-77
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    • 2008
  • Microcellular foaming plastics create a sensation at polymer industrial for lowering product costs and overcoming a lowering of mechanical intensity. Among many advantages, microcellular foaming plastics is well known to have a good acoustical properties. This research based on the experiment of sound absorption and transmission characteristics inquire into acoustical properties of microcellular foaming plastics. Difference of transmission loss of microcellular foaming plastics and solid materials was defined as cell effect. Also, cell effect is expressed by sound reflection and sound absorption. This study is expected to fundamental research to present economical, functional alternative plan for products using sound absorption and transmission materials.