• 한국소음진동공학회논문집
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• 제17권8호
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• pp.683-692
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• 2007

Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more noise owing to their lower material density. Internal aerodynamic noise from an idle speed control actuator(ISA) is qualitatively analyzed by using a scaling law, which is expressed with some flow parameters such as pressure drop, maximum flow velocity, and turbulence kinetic energy. First, basic flow characteristics through ISA passage are identified with the flow predictions obtained by applying computational fluid dynamics techniques. Then, the effects on ISA passage noise of each design factors including the duct turning shape and vane geometries are assessed. Based on these results, the preliminary low noise design for the ISA passage are proposed. The current method for the prediction of internal aerodynamic noise consists of the steady CFD and the scaling laws for the noise prediction. This combination is most cost-effective, compared with other methods, and therefore is believed to be suited for the preliminary design tool in the industrial field.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 2호
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• pp.433-438
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• 1999

본 논문은 기계장치에서 발생하는 소음 중 불필요한 소음만을 제거하고 실제로 필요한 소음(경고음 작동음 등)의 정보를 가진 소리는 제거하지 않는 소음 제어 방법을 Active Noise Control(ANC)를 이용하여 구현하였다. 소음원으로는 축류팬(Akial Fan)을 사용하였으며 여기서 발생하는 BPF를 효과적으로 제어할 수 있는 Feedback Active Noise Control 방식을 사용하였으며 적응 알고리즘으로 Filtered-X LMS 알고리즘을 사용하였다. 실험은 두 가지 Case(덕트 내 전파 소음, 외부 자유 음장 방사 소음)로 실행되었다. 제거하고자하는 대상은 BPF 소음이며 이 이외의 주파수에는 영향을 주지 않게 하기 위하여 대역필터를 이용하였다. 또한 실제 인간이 느끼는 소음 감소 효과를 알아보기 위해 Loudness로 제어 전후의 결과를 비교하였다. 실험 결과 BPF만 감소시키고 BPF이외의 주파수에는 영향을 주지 않음을 알 수 있었으며 6.7dB의 Loudness level의 감소 효과를 얻어, 제어하고자 하는 주파수만을 제어하였으며 음압뿐 아니라 인간이 느끼는 소음도에서도 효과적으로 감소할 수 있음을 확인할 수 있었다.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.15-23
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• 2000

The present work describes the prediction method for the unsteady flow field and the acoustic pressure field of a ducted axial fan. The prediction method is comprised of time-marching free-wake method, acoustic analogy, and the Kirchhoff-Helmholtz BEM. The predicted sound signal of a rotor is similar to the experiment one. We assume that the rotor rotates with a constant angular velocity and the flow field around the rotor is incompressible and inviscid. Then, a time-marching free-wake method is used to model the fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The newly developed Helmholtz-Kirchhoff BEM lot thin body is used to calculate tile sound field of the ducted fan. The ducted fan with 6 blades is analysed and the sound field around the duct is calculated.

• 소음진동
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• 제9권1호
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• pp.184-188
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• 1999

Noise regulation of heavy construction machinery is getting stricter： 3 dB per every 4 year in European community. To meet this requirement many engineers have adopted the enclosing structures with thick absorbing materials and small opening, This increases internal temperature of the enclosure which have engine systems such as electric equipment that are vulnerable to heat, and engine block and muffler that can be regarded as heat sources. So noise control engineers have to consider a coupling problem: combining heat balance and noise reduction. This paper describes this approach by introducing simple heat transfer theory and SEA. The enclosing system of the loader whose enclosing structure consists of two rooms is investigated to show the validity of this method. The results represent that the simple heat transfer theory can be useful to estimate cooling performance when it is linked together by the back pressure theory in duct system. and the radiated noise can also be estimated by the SEA. Therefore a designer can use these approaches to define the opening ratio of an enclosure and the mass flow rate of air considering radiating noise.