• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.340-341
• /
• 2010

Noise reduction is an important factor to design low noise sensor array. In this paper three layers of the de-coupler in the conformal sensor array were used to investigate noise reduction. Conformal sensor array is positioned in the layers and the distance from the layer is 0.25cm~1.5cm. Transfer function in the frequency density function is investigated according to the three different positions. When increasing the embedded distance the flow noise decreased in the region of the kx>10.

• 유체기계공업학회:학술대회논문집
• /
• 2002.12a
• /
• pp.123-128
• /
• 2002

Over the range(OTR) has been applied for cooking and ventilation functions especially in northern Amarica. Because flow rate and operating rpm of the double sided sirocco fan for ventilation are much higher and than the microwave oven system, the major noise source is the sirocco fm. Recently, the quiet fan development is one of very important issues for amenity. In this study, the noise source identification using multi-microphone array system was carefully carried out and numerical simulations for understanding the aerodynamic and aeroacoustic of the fan were peformed. The sound level of tonal noise is predicted with a good accuracy but that of the broadband shows some discrepancy. In order to reduce the broadband noise, the inlet region of sirocco fan have to be modified that the secondary flow should be suppressed. Based on these results, new low noise fan and OTR is now developing.

• Journal of KSNVE
• /
• v.7 no.6
• /
• pp.888-893
• /
• 1997

진공청소기에서 발생하는 주 소음원은 홴(fan)에 의한 공력 소음및 모터의 진동에 기인하는 청소기 본체의 소음과 청소기 흡입 노즐(nozzle)에서 발생하는 공력 소음으로 나눌수 있다. 청소기 본체의 주 소음원인 원심 홴(centrifugal fan)은 고속으로 회전하며 구조가 복잡함으로 인해 소음 해석에 필수적인 유동의 해석이 어려우나 이산 와류법을 이용한 소음원 해석등의 연구가 진행중이다. 진공청소기 노즐부에서는 일반적인 분류(jet)의 토출과는 상이하게 공기를 흡입하는 구조로 소음 발생 기구의 모델링 (modeling)에 대한 연구는 거의 전무하다. 공력 소음은 Lighthill에 의하면 비정상 유체가 운동할 때 나타나는 변형에 기인한다고 하며 주변에 고정 경계면이 없는 상태에서 유체가 흐를 때 발생하는 소음을 이론적으로 연구하였다. 그후 Curle에 의해서 고체 벽면의 영향을 고려한 방정식의 해가 구해졌다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.802-805
• /
• 2007

The exhaust system, including a muffler, is one of the major sources to generate the radiated noise of construction equipment. The muffler is generally known that it reduces the exhaust noise level, but it sometimes increases the noise level because of the flow effect inside a muffler. So, it is required to consider the flow effect inside a muffler to reduce the exhaust noise level of construction equipment. In this paper, an experimental method to consider a quantitative flow effect inside a muffler was set up through a series of tests. Finally, the experimental result was verified through the flow noise analysis using CFD analysis result. These results make it possible to understand the dynamic characteristics of the flow noise and to design the low noise muffler for the construction equipment.

• Journal of Korean Society for Quality Management
• /
• v.28 no.1
• /
• pp.41-56
• /
• 2000

Recently, the regulations from the government and concerns of the people give rise to the interest in noise from a passengers car In this paper, Taguchi method is adopted to reduce the noise from the intake system of a cu. Based on the current design of the intake system, the factors such as the length and radius of each component of the intake system, which are thought to be effective for the system are arranged using L$_{18}$ table of orthogonal array Moreover, the non-controllable factors are included for the analysis. Thus, the relation between control factors and non-controllable factors are analyzed with constraints..

• Journal of KSNVE
• /
• v.11 no.1
• /
• pp.15-20
• /
• 2001

홴(fan)은 모터로부터 회전력을 전달받아 공기동력인 풍량과 정압을 발생시켜 발열부품의 냉각 및 환기용으로 산업현장과 가전기기에서 널리 사용되고 있다. 과거 산업현장에서 주로 사용되어지던 송풍기가 가전기기에 적용되면서 홴에 대한 관심이 더욱 증폭되었는데 특히 국내에서 독자적인 소형 홴 연구가 본격적으로 시작된 것도 이 때이다. 가전에서의 홴은 고효율 뿐 만 아니라 주로 저소음화에 대한 연구에 초점이 맞추어져 있는데 이는 기존의 산업현장의 송풍기가 주로 풍량과 정압에 목표를 두고 개발해 왔던 것도 한 이유지만 구조적인 안정성 때문에 소음을 고려한 설계가 한계가 있었기 때문으로 저소음홴에 대한 응용기술이 충분히 발달하지 못했기 때문에 송풍기 기술을 그대로 받아들인 초창기 가전용홴은 소음이 높았다. 또한 가전기기는 모든 연령층이 사용하기 때문에 소음이 큰 제품은 항상 소비자 클레임의 원인이 되기 때문이다.(중략)

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.12
• /
• pp.31-39
• /
• 1999

Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.

• Journal of KSNVE
• /
• v.11 no.2
• /
• pp.234-240
• /
• 2001

Recently, the regulations from the government and the concerns of people be raised to the interest in exhaust and intake noise of passenger car as much as other vehicles. In these demands, performance prediction software was developed in this paper. In this study, Robust design was used for improving the noise reduction capacity of intake system with the performance prediction software. On the basis of the existing design, length and radius of each component that was thought to be effective to the performance of intake system was selected. At first, factors are arranged by using Ll8 table of orthogonal array and then optimum value can be obtained by modified Ll6 table of orthogonal array.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.279-284
• /
• 2002

In this study, it has been developed the program for predicting the noise spectrum of axial flow fan. The radiated acoustic pressure is expressed the discrete frequency noise peaks at BPF(Blade passage frequency) and its harmonics by Wu's method and the line spectrum at the broad band by Wright's method. And this paper presents the characteristics of a fan noise due to modify the design parameters. Accordingly, it is obtained the design parameter values for noise reduction of fan.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.641-645
• /
• 2002

저소음 팬의 설계는 팬 성능의 저감 없이 이루어져야 한다. 따라서 저소음 팬 설계는 기본적으로 다분야간 설계 최적화 또는 다목적 설계 최적화의 문제이다. 본 연구에서는 이러한 요구를 수행하기 위해 반응면 기법을 저소음 축류 팬 설계에 적용하여 보았다. 또한 이러한 설계 단계에서 필요한 수백가지 시험 결과를 효과적으로 구하기 위해 효율적인 유동 해석 툴과 소음 해석 툴을 개발하여 적용시켰다. 마지막으로 이렇게 설계된 팬을 실제 크기로 제작 측정 비교 분석하여 적용된 기법을 검증하며 문제점에 대해 고찰해 보았다.