• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.2
• /
• pp.205-213
• /
• 2011

The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 dBA. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.6
• /
• pp.117-122
• /
• 2017

Cabin noise due to the electric powertrain of electrical vehicle may consists of motor noise caused by electrical mismatch and gear noise coming from reduction gearbox. These sound may be considered rather small noise compared to those of internal combustion engine, but without masking effect, the noise can be more annoying for customer. Thus, this paper demonstrates the characteristics of electrical vehicle powertrain noise, and the effect of passive damping material for the noise reduction. The typical motor noise can be affected by the motor torque. Also, it is demonstrated that the reduction gearbox may be a weak point for the noise path compared to the motor housing. With vehicle test, it is shown that the damping patch is more effective for noise reduction with deceleration condition than with acceleration condition.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.1
• /
• pp.17-21
• /
• 2011

The effects of screening hydrophones with open-cell foams for reduction of the infrasonic self-noise induced by the flow around hydrophones are investigated by at-sea experiment. Test results of the 10 ppi polyurethane open-cell foams with different thickness show that the foams of 1 cm and 3 cm thickness reduce the flow-induced self-noises up to 20 dB and 28 dB at the frequency band of 2-10 Hz, respectively.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.223-226
• /
• 2000

흡기 럼블 소음의 발생원을 규명하고 흡배기계와 엔진을 포함한 1-D 모사 실험을 통하여 흡기럼블 소음을 저감하기 위한 다기관의 구조를 제안하고 실험을 통하여 확인하였다. 흡기 럼블 소음은 다기통 엔진에서 기통간 흡입 편차 외에도 쓰로틀 바디로부터 각 연소실 흡기 밸브 사이의 거리 편차를 인하여 발생하고 거리 편차를 줄여 제작된 흡기 다기관에서 Half Order 성분이 저감되어 럼블 소음이 저감되었다.

• Journal of the KSME
• /
• v.53 no.2
• /
• pp.49-53
• /
• 2013

철도차량은 중요한 친환경 대중교통 수단으로서 운행 구간이 확장되고 있다. 그러나 철도선로가 거주지역을 통과하여 설치되면서 환경 소음 문제가 야기되고 있으며 이의 저감이 중요한 이슈 중 하나이다. 철도차량 및 궤도에서 발생하는 전동음은 저감해야 할 주요 소음원 중 하나이다. 따라서 철도의 진동 및 소음 관련된 연구현황들에 대해 알아보고 궤도 지지단을 고려한 레일의 진동과 방사 소음 특성을 예측하고 궤도 모니터링 시스템 개발에까지 적용이 가능한 방법들에 대한 연구가 필요하다.

• Journal of the KSME
• /
• v.33 no.2
• /
• pp.171-182
• /
• 1993

소음을 현저히 저감하기 위해서는 상품의 원가상승, 고효율화 및 상품의 외곽크기 콤팩 트(compact)화에 제약을 받기 때문에, Q(품질 : quality), C(가격 : cost), D(납기 : delivery)를 만족하는 기술개발과 상품개발의 노력이 매우 필요하게 된다. 따라서 국내 . 외 가전업체에서는 소음을 줄이기 위한 심도있는 연구가 많이 진행되고 있으며, 이를 반영한 상품 출시도 매우 빠 르게 변화하고 있는 추세이다. 이 글에서는 에어콘 저소음화에 관련한 각종 기술자료 및 논문 들을 토대로 하여 가정용 에어콘에서의 소음발생의 종류 및 각각의 소음발생 원인에 대해 소개 하고, 그 저소음화 대책 기술 동향을 매우 제한된 범위내에서 서술하였다.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.2
• /
• pp.150-159
• /
• 2002

The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. Piezoelectric smart panel is basically a plate structure on which piezoelectric patch with shunt circuits is mounted and sound absorbing material is bonded on the surface of the structure. Sound absorbing materials can absorb the sound transmitted at mid frequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to tune the piezoelectric shunt circuit, the measured electrical impedance model is adopted. Resonant shunt circuit composed of register and inductor in stories is considered and the circuit parameters are determined based on maximizing the dissipated energy through the circuit. The transmitted noise reduction performance of smart panels is investigated using an acoustic tunnel. The tunnel is a square crosses sectional tunnel and a loud speaker is mounted at one side of the tunnel as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across the panels is measured. Noise reduction performance of a double smart panel possessing absorbing material and air gap shows a good result at mid frequency region except the first resonance frequency. By enabling the piezoelectric shunt damping, noise reduction is achieved at the resonance frequency as well. Piezoelectric smart panels incorporating passive method and piezoelectric shunt damping are a promising technology for noise reduction in a broadband frequency.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.3 no.1
• /
• pp.49-57
• /
• 2002

The possibility of a transmission noise reduction of piezoelectric smart panels using piezoelectric shunt damping is experimentally studied. Piezoelectric smart panel is basically a plate structure on which piezoelectric patch with shunt circuits is mounted and sound absorbing materials are bonded on the surface of the structure. Sound absorbing materials can absorb the sound transmitted at mid frequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to reduce the sound transmission at low panel resonances, piezoelectric damping using the measured electrical impedance model is adopted. Resonant shunt circuit for piezoelectric shunt damping is composed of register and inductor in series, and they are determined by maximizing the dissipated energy throughout the circuit. The transmitted noise reduction performance of smart panels is investigated using an acoustic tunnel. The tunnel is a tube with square crosses section and a loud-speaker is mounted at one side of the tube as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across panels is measured. Noise reduction performance of a smart panels possessing absorbing material and/or air gap shows a good result at mid frequency region but little effect in the resonance frequency. By enabling the piezoelectric shunt damping, noise reduction of 10dB, 8dB is achieved at the resonance frequencise as well. Piezoelectric smart panels incorporating passive method and piezoelectric shunt damping are a promising technology for noise reduction in a broadband frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1994.10a
• /
• pp.80-85
• /
• 1994

전 세계적으로 환경에 대한 관심이 고조됨에 따라 육상 교통 기관, 건설 장비, 심지어 가전 제품에 있어서도 소음 문제에 대한 관심이 크게 대두되고 있다. 특히, 수출을 하기 위해서는 그 나라의 소음 규제법을 만족시켜야 하며 제품의 경쟁력을 위해서는 그 이상의 것이 요구되고 있다. 또한, 소음 문제는 소비자의 제품 구매 선택에 영향을 주기도 한다. 일본의 경우 JIS 규격으로 건설 장비의 소음을 규제하고 있으며, 소음 수준에 따라 일반 장비, 저 소음 장비, 초 저소음 장비로 구분하여 장비에 따라 건설 작업을 제하하기도 하며, 특히 초 저소음 장비 인증을 받은 것은 장비 사용 단가 및 사용에 있어 차등을 두어 혜택을 주고 있다. 본 논문에서는 현재 크롤러 굴삭기에 대해 시행중인 유럽 소음 규제법 86/662/EEC 보다 강화되어 '97년부터 적용 예상되고 있는 89/514/EEC 소음 규제에 대비하여 크롤러 굴삭기의 소음 저감 대책을 논하고자 한다.

• Journal of Drive and Control
• /
• v.2 no.3
• /
• pp.20-27
• /
• 2005