• Title/Summary/Keyword: Sound Pressure

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An Analysis of the Acoustic Radiation Characteristics from the Acoustic Transducer (압전세라믹스를 이용한 음향트랜스듀서의 음향방사특성 해석)

  • 노현택;고영준;박재성;남효덕;장호경
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.703-706
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    • 2000
  • The acoustic characteristics radiated from the acoustic transducer with metal-piezoceramic laminated circular plate were simulated. The Vibrational modes of metal-piezoceramic laminated circular plates were calculated by using the finite element method. After meshing the inside closed boundary of the acoustic transducer, the pressure gradients and the isotaric lines were calculated for the various frequencies. It has been observed that the characteristics of the sound pressure calculated for the various frequencies. Also, the directivity patterns and the sound pressure radiated from the acoustic transducer were calculated by 2-dimensional analysis.

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Prediction of Radiated Sound on Structure-acoustic Coupled Plate by the Efficient Configuration of Structural Sensors (구조센서의 효율적인 구성을 통한 구조 음향연성 평판의 방사음 예측)

  • Lee, Ok-Dong;Oh, Jae-Eung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.9
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    • pp.695-705
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    • 2014
  • In this paper, two types of techniques for the prediction of radiated sound pressure due to vibration of a structure are investigated. The prediction performance using wave-number sensing technique is compared to that of conventional prediction method, such as Rayleigh's integral method, for the prediction of far-field radiated sound pressure. For a coupled plate, wave-number components are predicted by the vibration response of plate and the prediction performance of far-field sound is verified. In addition, the applicability of distributed sensors that are not allowable to Rayleigh's integral method is considered and these can replace point sensors. Experimental implementation verified the prediction accuracy of far-field sound radiation by the wave-number sensing technique. Prediction results from the technique are as good as those of Rayleigh's integral method and with distributed sensors, more reduced computation time is expected. To predict the radiated sound by the efficient configuration of structural sensors, composed(synthesized) mode considering sound power contribution is determined and from this size and location of sensors are chosen. Four types of sensor configuration are suggested, simulated and compared.

Sound Quality Characteristics of Refrigerator Noise in Real Living Environments (주거환경에서 냉장고 소음의 음질 특성)

  • You, Jin;Chang, Ho-Yeon;Lee, Chung-Hwa;Jeong, Jeong-Ho;Jeon, Jin-Yong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.8 s.113
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    • pp.797-805
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    • 2006
  • The sound quality characteristics of refrigerator noise in an anechoic chamber and in a real living environment for 30 models of refrigerators were investigated. Subjective evaluation experiments were conducted to determine subjective tolerance level for refrigerator noise. Refrigerator noise was played from a loudspeaker at the position normally occupied by a refrigerator in a real living environment. A nine-point scale was used to measure subjective satisfaction of the sound pressure levels for refrigerator noise. Point 3 on the scale corresponded to a sound pressure level of about 30 dB(A). Seventy percent of the participants were satisfied with this level of refrigerator noise. A semantic differential test was also conducted to evaluate the sound quality of refrigerator noise. From the results of correlation and multiple regression analyses on the psychoacoustical parameters and subjective evaluations of 30 refrigerators, sound quality indices which predict the subjective rating score were proposed.

Self-Excited Noise Generation from Laminar Methane/Air Premixed Flames in Thin Annular JetsPut (환형제트에서의 메탄과 공기의 층류 예혼합 화염에서 발생되는 자발적인 소음에 대한 실험적 연구)

  • Jin, S.H.;Joung, J.H.;Kwon, S.J.;Chung, S.H.
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.159-165
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    • 2003
  • Self-excited noise generation from laminar flames in thin annular jets of methane/air premixture has been investigated experimentally. Various flames were observed in this flow configuration, including conical shape flames, ring shape flames, steady crown shape flames, and oscillating crown shape flames. Self-excited noise with the total sound pressure level of about 70dB was generated from the oscillating crown shape flames for the equivalence ratio larger than 0.95. Sound pressure and $CH^{\ast}$ chemiluminescence were measured by using a microphone and a photomultiplier tube. The frequency of generated noise was measured as functions of equivalence ratio and premixture velocity. A frequency doubling phenomena have also been observed. The measured $CH^{\ast}$ chemiluminescence data were analyzed from which the corresponding sound pressure has been calculated. By comparing the data with those of measured ones, the noise source can be attributed to the flame front fluctuation near the edge of the oscillating crown-shape flames. The flame stability regime was influenced sensitively to the supplying air through the inner tube.

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Complex envelope of sound field and its application (음장의 복소 포락과 응용)

  • Park, Choon-Su;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.502-505
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    • 2006
  • Acoustic holography allows us to predict spatial pressure distribution on any surface of interest from measured hologram. It is noteworthy that the data size is so huge that it takes long time to calculate pressure field. Moreover the reconstructed pressure field is frequently too complicated to get what we want to know. One possible candidate is complex envelope. Complex envelope in time domain is well known and widely used in various engineering field. We have attempted to extend this method to space domain, so that we can have rather simple spatial pressure picture that provides information we need, for example, where sound sources are. First we start with the simplest case. We examine the complex envelope of a plane wave on both space and wave number domain. Then we extend to monopole case. Holographic reconstructed sound field on the monopole is processed according to what we propose. We demonstrate how this method provides better picture for analyzing the sound field.

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A Experimental Comparison Analysis for the Characteristics of Impulse Noise Caused by Shooting of Small Arms (소구경 화기의 사격음 특성에 대한 비교분석 연구)

  • Park, Mi-You;Shim, Cheul-Bo;Hong, JunSeok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.5
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    • pp.578-583
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    • 2016
  • In order to provide a basis data for design of small arms and their silencer, an experimental study on firing noise of small arms was performed around the muzzle of a gun. For this experimental comparison analysis, the target small arms were included most operating small arms in our country. The sound pressure levels were measured at a certain distance which was predetermined according to US army firing test procedure, TOP 3-2-045. By this experimental study, the sound pressure levels of 5.56 mm caliber small arms are 143 dB ~ 145.4 dB and 7.62 mm caliber small arms are 144 dB ~ 145.2 dB. Between the heavy machine gun K12 and M60, the sound pressure level of K12 is slightly lower than M60.Also silencer for K14 snifer rifle was tested. Using this result, it has been found that the reduction effect of the silencer is 15.4 dB but the improvements of silencer performance in the high frequency range have to be studied later on.

Optimal Design and Analysis of a Class IV Flextensional Transducer (Class Flextensional 트랜스듀서의 최적설계 및 특성해석)

  • 강국진;노용래
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.4
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    • pp.69-76
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    • 2000
  • In this research, with the FEM we analyzed the variation of the sound pressure and thermal distribution of a Class IV Flextensional transducer in relation to its material properties and structures. Based on the results, we determined optimal structure of a Class IV Flextensional transducer that had maximum sound pressure, minimum thermal distribution, and 1 kHz resonance frequency. The sound pressure by the optimal structure is higher than that of the basic structure by two times, and the thermal distribution is much lower. Results of the present work can be utilized to design Class IV Flextensional transducers of various resonance frequency, maximum sound pressure, and minimum thermal distribution.

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A Study on Development of a Prediction Model for the Sound Pressure Level Related to Vehicle Velocity by Measuring NCPX Measurement (NCPX 계측 방법에 따른 속도별 소음 데시벨 예측 모델 개발에 대한 연구)

  • Kim, Do Wan;An, Deok Soon;Mun, Sungho
    • International Journal of Highway Engineering
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    • v.15 no.4
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    • pp.21-29
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    • 2013
  • PURPOSES : The objective of this study is to provide for the overall SPL (Sound Pressure Level) prediction model by using the NCPX (Noble Close Proximity) measurement method in terms of regression equations. METHODS: Many methods can be used to measure the traffic noise. However, NCPX measurement can powerfully measure the friction noise originated somewhere between tire and pavement by attaching the microphone at the proximity location of tire. The overall SPL(Sound Pressure Level) calculated by NCPX method depends on the vehicle speed, and the basic equation form of the prediction model for overall SPL was used, according to the previous studies (Bloemhof, 1986; Cho and Mun, 2008a; Cho and Mun, 2008b; Cho and Mun, 2008c). RESULTS : After developing the prediction model, the prediction model was verified by the correlation analysis and RMSE (Root Mean Squared Error). Furthermore, the correlation was resulted in good agreement. CONCLUSIONS: If the polynomial overall SPL prediction model can be used, the special cautions are required in terms of considering the interpolation points between vehicle speeds as well as overall SPLs.

An Experimental Study on the Optimistic Recognition Level of Public Address System as a Soundscape Application Facility (사운드스케이프 적용을 위한 옥외 P.A. 시스템의 적정 인지레벨에 관한 실험적 연구)

  • Song, Min-Jeong;Jang, Gil-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.11
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    • pp.1050-1055
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    • 2007
  • P.A.(public address) system is considered as an useful active soundscape appliance which can gives a place identity and vitality by introducing conventional musics, environmental musics, bird singing sounds etc. In this study, the main aim is to know the optimistic distance from the speaker and sound pressure level range of introducing sound. So, the sound pressure level of P.A. system due to distances were measured and subjects' responses with level variations were checked. The main results are as follows. Level range from 64 dB to 71 dB is comfortable for subjects. And the optimal level of introducing sound is related with sound source characteristics. The results of this study could be used for street furniture location design and P.A. system output level.