• Title/Summary/Keyword: 소음 감소

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An experimental investigation into the mechanism of the refrigerator contraction-expansion noise (냉장고 수축팽창 소음의 발생기구에 대한 실험적 규명)

  • Lee, Yeong-Gyu;Kim, Won-Jin
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.4
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    • pp.389-396
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    • 2022
  • This paper aims to identify the causes and mechanisms of contraction-expansion noise in refrigerators and proposes noise reduction methods. Contraction-expansion noise generated in refrigerators is mainly due to stick-slip phenomenon occurring on the contact surface between inner parts. Friction experiments were conducted to identify the factors causing the stick-slip phenomenon. Furthermore, the vibration level of the internal components was measured to determine the characteristics and location of the contraction-expansion noise. Based on the experimental results, experiments have been conducted to verify the noise characteristics for each factor. From this, it was confirmed that the friction experiment and the refrigerator contraction-expansion noise generation location and frequency were the same. The vibration level also increased as the vertical force was increased due to load loading. Also, it was confirmed that the contraction-expansion noise was reduced when the surface roughness was increased. Therefore, it was concluded that increasing the surface roughness of the contact surface in the same way as the results of the friction experiment was the method of reducing contraction-expansion noise.

The Noise Level Assessment of Dental Equipment (치과 의료장비의 소음 수준 평가)

  • Lee, Jeong-Suk;Han, Ye-Seul;Cho, Young-Sik
    • Journal of dental hygiene science
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    • v.15 no.5
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    • pp.603-611
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    • 2015
  • This research is aimed at cutting off hearing loss and other harmful factors due to noise and providing basic material for noise reduction plan. As the research method, this research assessed noise by measuring acoustic pressure level and frequency in various situation of non-treatment and treatment. As the measurement result, average noise degree of high speed handpiece of non-treatment, ultrasonic waves scaler, and low speed handpiece showed 58~66 dB(A). Average noise degree of scaling of treatment, tooth elimination, and denture adjust showed 73~81 dB(A). The result is inferior to recognized standards of noise induced hearing loss. But the result of assessing this with (noise rating) NR curve was NR-73~78, which exceeded general workplace noise standard. This level can cause hearing loss when exposed to a long time. Therefore, treatment office noise during dental treatment can cause psychological and physical damage in dental clinic employees, and it is urgently required to establish systematic and active noise reduction plan.

Investigation of the BSR Noise characteristics in Seat Cushion-frame with respect to Vibration Durability Test Using Multi-simulator (다축 가진기를 이용한 시트 쿠션 프레임의 내구 전후 BSR 진동특성 연구)

  • Choi, Ho-Il;Nam, Jae-Hyun;Kang, Jae-Young;Park, Jung-Hee
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.8
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    • pp.4776-4783
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    • 2014
  • Many studies have examined the reduction of primary noise sources, but quality-related noise, such as BSR, is rarely studied. This study describes the quantitative BSR test method using a multi-axial simulator. The sine sweep test was conducted to detect the system resonance and its relation to BSR noise with high frequency. This method is applied to the seat frame with/without the vibration durability test. The results showed that the 1st lateral resonance leads to higher BSR frequency noise. In addition, the reduction of the lateral mode system stiffness after the durability test results in a decrease in the BSR noise in sine sweep test mode.

Study on Tip-Vortex Cavitation and Its Noise Characteristics - Effects of Surface Roughness - (타원형날개끝 캐비테이션과 유기소음 특성연구 - 표면거칠기의 영향 -)

  • B.S. Hyun;C.M. Lee;H.S. Choi
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.1
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    • pp.84-93
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    • 1994
  • The purpose of present study is to investigate the surface roughness on tip-vortex cavitation and its induced noise, emanating from an elliptic wing of NACA 0012 section. Roughness elements of 200μm are applied to the 10% portion of wing tip, and then, the wing tip as well as the leading edge. It is shown from cavitation observation that the cavitation inception is first visible at about half chord downstream of wing tip for most experimental conditions, and developed into the tip-vortex cavitation and finally the fully developed cavitation as cavitation number is decreased. Acoustic noise generated by a tip-vortex cavitation has its frequency range of 3 kHz to 50 kHz, while the fully-developed cavitation at lower cavitation number induces a broad band spectrum. It is also shown that, when the roughness elements are applied to the wing tip and the leading edge, the cavitation characteristics and its induced noise are improved. Moreover, it is appeared that the condition at which the rough surface is at pressure side gives a better result. although its lift-drag ratio is reduced.

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Study on Elevator Induced Structural Vibration Reduction Performance Using Polymer Concrete (폴리머 콘크리트를 이용한 엘리베이터 기인 구조 진동저감 성능 연구)

  • Yeom, Jihye;Kim, Jeong-Jin;Park, Junhong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.90-94
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    • 2021
  • With the increased interest on quiescent place for residential place, the noise generation from facilities needs to be minimized. One important noise source include sounds from operation of elevators. The elevator operates between floors and generates significantly annoying sounds to the nearby living spaces. It is recognized as the significant contributor inducing noise annoyance to residents. Elevator is supported to the building structure at several locations for movements between floors. In this study, the vibration reduction by use of polymer concrete on the support location was demonstrated. By measuring and comparing the vibration generation when supported on cement and polymer concrete, the noise reduction performance was evaluated. The polymer concrete was made in the form of being inserted into the wall that imitates the hoistway. The impact vibration was induced to the bracket and vibration transfer magnitude was measured. The damping ratio was evaluated through normalization and curve fitting of transient response, and comparison was performed for each resin mixing ratio. By use of polymer concrete, it was possible to reduce the vibration generation in an effect manner without sacrifice on the structural rigidity.

A Study on Reduction of Sound Noise Induced by Disk Rotation in Optical Disk Drives (광 디스크 드라이브의 공력소음 감소에 관한 연구)

  • 송인상;박건순;최학현;김수경;이승엽
    • Journal of KSNVE
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    • v.9 no.4
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    • pp.693-702
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    • 1999
  • We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

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Noise Reduction of Range Hood in Kitchen Ventilation System (주방 환기 시스템에서 렌지 후드의 소음 감소 방안)

  • 최영석;김철호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.848-851
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    • 2004
  • This paper studied a method for minimizing the noise level emitted from range hoods. Range hoods were used for discharging various hazardous materials generated during household cooking to the outdoors, thus preventing them from being diffused through rooms in the house since they are the main cause of air pollution within dwellings. This study assumed that static pressure was not applied at the discharge outlet of the range hood. As such, the range hood was installed on the wall without the use of a connecting duct or other connectors attached to its discharge outlet. The vibration having the greatest influence on the noise level was determined by measuring the vibration at the front side of the hood where the acoustic omission was at its maximum. A method was then proposed to reduce the noise by simply suppressing the vibration at the vibrating part.

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ANALYSIS OF PERMANENT MAGNET OVERHANG EFFECT BY USING 3D FEM IN THE POINT OF NOISE AND VIBRATION (3차원 유한요소법을 이용한 BLDC 모터의 영구 자석 오버행에 의한 소음 및 진동 특성)

  • An, Young-Gyu;Kang, Gyu-Hong;Kim, Gyu-Tak
    • Proceedings of the KIEE Conference
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    • 2006.07b
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    • pp.831-832
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    • 2006
  • 본 논문에서는 Brushless DC Motors(이하 BLDC Motor이라 함)의 영구 자석의 오버행에 따른 진동, 소음 특성에 대하여 다루었다. 비대칭 오버행 구조에서는 Z축 방향 힘이 발생한다. 이는 베어링에 손상을 입힐 뿐 아니라 큰 노이즈와 진동을 유발시킨다. 따라서 진동과 소음의 감소를 위한 자석 오버행 효과 해석이 필수적이다. 본 논문에서는 비대칭 영구 자석 오버행 효과를 해석하고 BLDC Motor에서 발생하는 소음과 진동을 분석하였고 비대칭 영구 자석 오버행 효과를 고려하여 Z축 방향의 영향력을 계산하기 위하여 3차원 유한요소법(3D FEM)을 사용하였다.

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