• Title/Summary/Keyword: Acoustic Noise Reduction

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A study on the performance test and acoustic design of interference type noise reduction device for railway noise (철도소음 저감을 위한 간섭형 방음장치 음향 설계 및 성능시험에 관한 연구)

  • Cho, Jun-Ho;Koh, Hyo-In
    • Journal of Environmental Impact Assessment
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    • v.20 no.6
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    • pp.787-795
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    • 2011
  • Noise barrier is generally used with welding of joint rail for railway noise reduction in our country. But the noise barrier for high speed railway has weak point in low frequencies about 315Hz band. In this study, For developing of Interference-type Noise Reduction Device(INRD), acoustic analysis were performed using commercial software. For verifying the improvement in the noise reduction, noise measurement before and after installing of INRD were performed in Anechoic Chamber. From these acoustic analysis and noise measurement, it was known that developed INRD has a good noise reduction performance and can be used efficiently with conventional noise barrier.

Vibration and Acoustic Noise Reduction Method of SRM Using Auxiliary Winding (보조권선 활용에 의한 SRM의 진동 및 소음 저감 방안)

  • 정태욱
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.11
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    • pp.548-556
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    • 2003
  • Switched reluctance motor(SRM) has simple magnetic structure, and needs simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase. In the vibration and acoustic noise characteristics. the considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural frequency of mechanical structure. This radial vibration force is generated by abrupt change of radial magnetic force in the phase commutation region. This paper studied about simple electromagnetic structure of SRM using auxiliary compensating winding for the reduction of noise and vibration. This auxiliary winding is coupled with all phase windings electromagnetically and absorb and transfer magnetic energy variation from phase to other phase. By this interaction of phase windings and compensating winding can reduce abrupt radial force change and vibration and acoustic noise. In this paper the improvement effect is examined by the test of prototype machine.

Design of Close-Fitting Acoustic Enclosure of Diesel Engine (디젤엔진의 근접 음향 차폐장치 설계 및 성능평가)

  • 류정수;정우진;전재진
    • Journal of the Korea Institute of Military Science and Technology
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    • v.2 no.1
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    • pp.82-89
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    • 1999
  • In this article, the performances of acoustic enclosure with double resilient mount system which was designed by ADD to reduce the radiated noise by main noise source of ships, was tested and evaluated. From test results, it was verified that the acoustic performances of acoustic enclosure satisfied the requirements; vibration isolation level at 1st stage mount system of 15 ㏈ and airborne noise reduction level of 20 ㏈ in broad band.

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Acoustic Source Power Control and Global Noise Reduction by Selection of Distribution and Impedance of Absorptive Materials in Acoustically Small Enclosures (흡음재의 배치와 임피던스 선정을 통한 음원 방사파워 제어와 전역 소음 감소)

  • 김양한;조성호
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.8
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    • pp.668-674
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    • 2004
  • The possibility of global noise reduction by the sound power control through selection of distribution and impedance of absorptive materials is discussed. It is necessary to investigate the relation between the global sound energy in the field and the total sound power radiated by sources. In the previous work,$^{(1.2)}$ the authors presented a useful design method to change boundary condition that can be useful to reduce noise in acoustically small enclosures. Changing boundary condition Is related to not only enclosure’s geometrical shape but also acoustical treatment on walls for example, attaching of impedance patches (ex: absorptive material). In many practical situations, we often meet situation to change acoustical treatment on walls. The possibility of total acoustic potential energy(globa1 noise) reduction by acoustic source power control is examined in an acoustically small cavity Using acoustic energy balance equation, the relation between global noise control performance and absorptive material’s arrangement/impedance is deduced. Numerical simulation is performed to interpret its physical meaning in terms of absorbent’s distribution and impedance.

A study on the acoustic performance test method using speaker of a noise reduction device for noise reduction of the 400km/h class high-speed railroad (스피커를 이용한 400km/h급 고속철도 소음저감용 방음벽 상단장치의 음향성능 시험방법에 관한 연구)

  • Yoon, Je-Won;Kim, Young-Chan;Jang, Kang-Seok;Eum, Ki-Young;Jang, Seung-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.04a
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    • pp.625-629
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    • 2014
  • For the purpose of the acoustic performance evaluation of noise reduction device(NRD) installed at the top of noise barrier for further decreasing of noise level of 400km/h class high-speed railroad(HEMU), the acoustic performance test method using speaker instead of really running railway vehicle was suggested in this paper. For this, noise source location and frequency spectrum of HEMU was analyzed through the field noise test. These data were used for the determination of speaker's installation positions and frequency correction values applied to the speaker noise source. And, 400 meters long NRD was installed at the site where HEMU will be running at a speed of 400km/h. Finally, the outdoor speaker test with and without NRD showed that this NRD could decrease noise level even more than 3dB(A). In the future, the acoustic performance results of NRD conducted with speaker test will be compared with that of field test for HEMU running at a speed of 400km/h.

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Acoustic Power Control of a Lightly-Damped Enclosed Sound Field

  • Kim, Woo-Young;Kim, Dong-Kyu;Hwang, Won-Gul
    • International Journal of Aeronautical and Space Sciences
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    • v.2 no.2
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    • pp.19-27
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    • 2001
  • This research attempts to find an active control strategy which reduces acoustic power and acoustic energy in lightly-damped enclosed sound field such as a vehicle compartment or an operating room of heavy industrial machinery. An active control strategy, which takes into consideration of the acoustic radiation power of the source as a cost function, is formulated and examined to find capability of reducing noise. An adaptive filtering algorithm for sound power control is suggested and implemented to control lightly-damped sound field. To verify the method, sound power based active noise control algorithm was implemented on a rectangular box with lightly-damped wall, and popular acoustic energy based control with modal coupling reduction was performed to compare the noise reduction performance. It was shown that a total sound power based strategy provides a practical mean for global noise reduction for lightly damped sound field.

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Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1146-1151
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.196-201
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

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Image Noise Reduction Using Structural Mode Shaping for Scanning Electron Microscopy

  • Hamochi, Mitsuru;Wakui, Shinji
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.2
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    • pp.28-33
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    • 2008
  • In a scanning electron microscope (SEM), outside acoustic noise causes image noise that distorts observations of the specimen being examined. A SEM that is less sensitive to acoustic noise is highly desirable. This paper investigates the image noise problem by addressing the mode shapes of the base plate and the transmission path of the acoustic noise and vibration. By arranging the position of the rib, a new SEM base plate was developed that had twisting as the 1st and 2nd modes. In those two twisting modes, vibration nodes existed near the center of the base plate where the specimen chamber is placed. Less vibration was transmitted to the chamber and to the specimen by the twisting modes compared to bending ones, which are the 2nd and 3rd modes for a rectangular plain base plate. An SEM with the developed base plate installed exhibited a significant reduction of image noise when exposed to acoustic noises below 250 Hz.

Control for Seek Time Reduction in Disk Drives (디스크 드라이브의 탐색시간 단축제어)

  • Kang, Chang-Ik;Chu, Sang-Hun
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.2
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    • pp.104-112
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    • 2002
  • Controllers for acoustic noise reduction in disk drives have been developed but they have slower seek time performance than time-optimal controllers. We propose a new seek servo controller that has acoustic noise reduction benefit and faster seek time performance than conventional controllers. The proposed controller is designed to make sure that head is moved with maximized acceleration and deceleration under the voltage limitation imposed on head-positioning motor and so it provides faster seek time than conventional controllers designed by considering the current limitation. The experimental results using a commercially available disk drive confirm that the use of the proposed controller results in foster seek time than conventional controllers for acoustic noise reduction.