• 제목/요약/키워드: sound wave

검색결과 573건 처리시간 0.026초

관내법 시험시 Air-Damping 이 흡음계수에 미치는 영향 고찰 (Investigation on the Effects of Air-Damping on the Sound Absorption Coefficients Measured in the Tube)

  • 정완섭;서재갑;이두희;황재호
    • 소음진동
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    • 제7권5호
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    • pp.797-801
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    • 1997
  • This paper raises issues in testing the absorption coefficients of sound-absorptive samples using the standing wave apparatus according to the Korean standard of KS F 2814. The standard code does not consider any effect of air-damping which is significant in testing relatively low sound-absorptive samples. This limitation has been shown to yield much variation of sound absorption coefficients for recent samples tests whose coefficients are less than 10%. An improved method of calculating the sound absorption coefficients is proposed in this work and its effectiveness in real test is also illustrated. Finally, the guideline for the modification of our national standard code KS F 2814 is proposed.

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음선 기법을 이용한 초음파 음장 해석 (Ultrasonic Field Analysis Using a Sound-Ray Method)

  • 문병환;김진오
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2001년도 추계학술대회논문집 II
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    • pp.1329-1334
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    • 2001
  • This paper deals with the application of a sound-ray method to the analysis of the sound field in an ultrasonic cleaner. In order to include the wave interference phenomenon, the method has been modified to consider the phase of sound rays, The improved algorithm has been implemented by developing a Visual C++ program, The algorithm has been verified by comparing the analysis results of BEM reported earlier. It has been shown that the algorithm can be used to calculate ultrasonic fields in a cleaning- container with an object to be cleaned.

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평균 유동을 고려한 1차원 그린 함수를 이용한 덕트 내부의 음장 예측 방법 (Prediction of Sound Field Inside Duct with Moving Medium by using one Dimensional Green's function)

  • 전종훈;김양한
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 추계학술대회논문집
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    • pp.915-918
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    • 2005
  • Acoustic holography uses Kirchhoff·Helmholtz integral equation and Green's function which satisfies Dirichlet boundary condition Applications of acoustic holography have been taken to the sound field neglecting the effect of flow. The uniform flow, however, changes sound field and the governing equation, Green's function and so on. Thus the conventional method of acoustic holography should be changed. In this research, one possibility to apply acoustic holography to the sound field with uniform flow is introduced through checking for the plane wave in a duct. Change of Green's function due to uniform flow and one method to derive modified form of Kirchhoff·Heimholtz integral is suggested for 1-dimensional sound field. Derivation results show that using Green's function satisfying Dirichlet boundary condition, we can predict sound pressure in a duct using boundary value.

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Development and Embodiment of Automatic Location Tracing Service for Rescue Requester

  • Kim, Sun-Hyo;Kim, Jung-Hun;Kim, Hee-Sun;Yoon, Sung-wook
    • Journal of Multimedia Information System
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    • 제8권1호
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    • pp.11-16
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    • 2021
  • This study developed a design to estimate the location of rescue demander using the sound system at disaster site, in the conditions of indoor positioning cannot be performed properly. It is a location tracing system through smart phone application. It generates sound wave information of rescuer at the rescue site, and it can be used as assistant means for indoor location tracing at the disaster site using sound wave receiving measurement technology.

근거리 음압의 공간 변환에 의한 음원의 음장 분포 해석 (Analysis of the Sound Source Field Using Spatial Transformation of the Sound Pressure in a Near-field)

  • 김원호;윤종락
    • 한국음향학회지
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    • 제22권8호
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    • pp.660-669
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    • 2003
  • 본 논문은 음원 근처의 홀로그램 평면에서 측정된 음압에 대한 상호 파워 스펙트럼으로부터 홀로그램 평면에서의 음압 분포를 구하고 획득된 음장을 공간 변환하여 음원의 음장을 구하기 위한 이론을 설명하였으며, 홀로그램 평면에서의 상호 파워 스펙트럼으로부터 모든 지점에서의 음압을 구하기 위해 비선형 방정식에 대한 Taylor 급수를 전개하고 Newton-Raphson 법을 이용하여 계산하는 방법과 음원 영역으로의 역방향 전파시 발생되는 오차를 줄이기 위한 파수 필터를 제시하였다. 무한 배플 내의 원판형 진동체 수중 음원에 대한 모의실험을 통해 결과를 고찰하고 제시된 이론을 검증하였다.

맞대기 용접부내의 인공 결함에서 초음파의 전파특성 (Propagation Characteristic of Ultrasonic on Slit Defect in Butt Joint)

  • 남영현
    • Journal of Welding and Joining
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    • 제14권6호
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    • pp.37-47
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    • 1996
  • An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of ultrasonic wave is related to determination of testing sensitivity, scanning pitch and defect location. This paper investigated the directivity of ultrasonic wave, which scattered from slit defect located in heat-affected zone (HAZ) in butt joint using visualization method. The directivity of shear waves scattered from slit defect were different according to probe direction (far defect, near defect) and probe position (forward movement, maximum echo position, backward movement). The difference of directivity of reflection wave was existed between 2 MHz and 4 MHz angle probes. In the case of 2 MHz angle probe, the directivity of reflection wave was appeared sharp form because of the relation wave length and defect size.

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음파진동 안마의자제품의 성능향상을 위한 판스프링의 효율적 설계 (Efficient Design of Plate Spring for Improving Performance of Sound Wave Vibration Massage Chair)

  • 김창겸;박수용;조은현;이동형
    • 산업경영시스템학회지
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    • 제42권4호
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    • pp.1-7
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    • 2019
  • The customer of massage chair is expanding day by day from middle age to all ages. In 2018, the market size was 700 billion KRW, an increase of 30 times over 10 years. However, most related SMEs suffer from excessive competition by the market monopoly of some major companies. In this situation, in order for a related company to survive, it is necessary to steadily research and develop new products. Founded in 2009, company L produces massage chairs for health and relaxation of customers. L's products use a sound wave vibration module that is favorable for human body, unlike other products that use vibration motor type. However, frequent breakdowns of massage chair due to the vulnerability of plate (leaf) springs, which play an important role in sound wave vibration modules, made sap its competitiveness. In this paper, we propose a method to design desirable plate spring structure by sequentially experimenting with five different plate springs. The results of this study are expected to contribute to improve the quality of plate spring and the reliability of sound wave vibration module. In the future, it is necessary to find a way to use it in the development of foot massage or scalp management device as well as continuous research to find optimal plate spring structure through various analysis.

음파진동기와 스위스볼을 이용한 허리안정화운동이 근육두께와 수축시간에 미치는 영향 (Effects of Lumbar Stability Exercise on the Muscle Thickness and Contraction Time Using Sound Wave Vibrator and Swiss Ball)

  • 김용수;이진명;박소현;박혜리;최민주;김세광;양회송;정찬주;유영대;전현주
    • 대한통합의학회지
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    • 제4권1호
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    • pp.85-97
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    • 2016
  • Purpose : The purpose of this study was to investigate the effects on the muscle thickness and contraction time using sound wave vibrator and swiss ball. Methods : This study was performed on 20 subjects. 20 subjects were divided into two groups; Lumbar stability exercise using sound wave vibrator exercise(n=10)(Group1), Lumbar stability exercise using Swiss ball exercise(n=10)(Group2). Both of the group performed the exercise 3 times a week for 5 weeks. The data was analyzed by the paired t-test to compare before and after difference of factors on each group and the Independent t-test to compare the between groups. Results : Both group were increased muscle contracture time on Straight Leg Rise(SLR) test (p<0.05). It means both group were increased lumbar stability. However, by comparing the between groups, there were no statistically significant difference about muscle thickness of multifidus and transverse abdominal.(p>0.05). Conclusion : As a result of this study, we suggest that the sound wave vibrator may be effective exercise tool for lumbar stability exercise like a swiss ball.

잘못된 초음파 센서 데이터를 여과하기 위한 음압 비교법 (Comparison of Sound Pressure for Detecting Incorrect Sonar Measurements)

  • 이경민;정완균
    • 제어로봇시스템학회논문지
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    • 제15권3호
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    • pp.273-279
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    • 2009
  • In this paper, we address the problem of detecting incorrect sonar measurements. We use ideas from the inconsistency of information among sonar measurements together with the sound pressure of the wave from the sonar sensor to develop a new method, called the comparison of the sound pressure (CSP), to detect incorrect sonar readings. The inconsistency of information in cells can be a clue that indicates candidates for incorrect measurements, and the sound pressure of the wave from the sonar sensor determines incorrect readings among the candidates. From various experiments, the proposed method is confirmed that it is better than existing method at deciding the state of sonar measurements.

Sound Propagation in 5CB Liquid Crystals Homogeneously Confined in a Planar Cell

  • Ko, Jae-Hyeon;Hwang, Yoon-Hwae;Kim, Jong-Hyun
    • Journal of Information Display
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    • 제10권2호
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    • pp.72-75
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    • 2009
  • The Brillouin spectrum of 4'-n-pentyl-4-cyano-biphenyl (5CB) liquid crystals homogeneously confined in a planar liquid crystal (LC) cell was measured using a 6-pass tandem Fabry-Perot interferometer. By adopting a special right-angle scattering geometry, the sound velocity of 5CB was estimated from the Brillouin shift without knowing the refractive index. The sound velocity of the longitudinal wave propagating along the direction of the directors aligned parallel to the glass plates of the LC cell was 1784${\pm}$7 m/s at 300 K. The attenuation coefficient $\alpha$ was estimated to be approximately $1.9{\times}10^6m^{-1}$, which is about twice as large as that of the longitudinal sound wave propagating along the direction perpendicular to the directors. The present method may be very useful in the evaluation of the elastic properties of the materials used in display devices, whose refractive indices are not known.