• 대한설비공학회지:설비저널
• /
• 제24권1호
• /
• pp.71-81
• /
• 1995

• 대한설비공학회지:설비저널
• /
• 제25권5호
• /
• pp.401-411
• /
• 1996

• 대한설비공학회지:설비저널
• /
• 제21권1호
• /
• pp.35-39
• /
• 1992

• 대한설비공학회지:설비저널
• /
• 제26권6호
• /
• pp.481-490
• /
• 1997

• 설비공학논문집
• /
• 제22권12호
• /
• pp.897-901
• /
• 2010

A silencer has been widely used for the purpose of suppressing the noises propagated from duct of air conditioning system. The absorption type silencer is usually applied to reduce the noise with high frequency bandwidth. On the order hand, the resonance type silencer is applied to reduce the noise with low-middle frequency bandwidth. The insertion loss of silencer is measured in the reverberation room. The cut-off frequency of reverberation room is 100 Hz. The insertion loss of absorption type silencer is more larger than that for resonance type silencer regardless of changing the flow velocity.

• 설비공학논문집
• /
• 제7권1호
• /
• pp.142-149
• /
• 1995

Axial fans are very useful cooling devices being widely used in many electric and industrial machinery. However those are often accompanying annoying noise. Many efforts have been devoted in order to reduce the fan noise. In this study, the procedure was devided into two major parts in considering effects of design parameters of axial fan concerned with noise ; the fan theory and the Fukano's fan noise study. By using the fan theory we defined stagger angle, camber angle, blade inlet and outlet angle for studying low noise fan. Then the effects of such angles on the flow rate and static pressure were investigated. By using the Fukano's fan noise theory, the relations of the chord length, the rotational speed and the number of blades vs. fan noise are investigated.

• 설비공학논문집
• /
• 제8권3호
• /
• pp.361-374
• /
• 1996

In general, a cooling tower has two major noise sources, one is the fan and the other is the falling water. The fan noise is produced by passage of its blades through the air and radiates from the fan stack. Noises from the falling water are caused by splashing and dropping of water cascading over the internal filler of the cooling tower and into the basin and radiate from the louvered face. In this paper, the noise measurements and its frequency analysis are carried out for the locations facing the louvered side and near the fan stack referring the related code and standards in order to study the noise characteristics of the induced-draft cooling tower, especially for the buildings. As a result, it is found that for every doubling of distance from the noise source the noise level decreases by 2~4dBA in the near field with reflect surfaces and decreases by about 6dBA also in the far field without reflect surfaces. As a supplement to the noise measurements, a computer program with simple algorithm is developed in order to estimate the noise level at a distance from the cooling tower, so that the user could apply and modify it for the particular boundary conditions easily.

• 설비공학논문집
• /
• 제13권7호
• /
• pp.621-626
• /
• 2001

The flow induced noise of the cross-flow fan with uniform/random pitch blades is predicted by computational methods. With the time dependent surface pressure data obtained by solving the incompressible Navier-Stokes equations in moving coordinates, the acoustic pressure is predicted by the Ffowcs Williams-Hawkings equation. The positions of the blade noise source are identified through an investigation of the acoustic pressure history induced by one blade, and it is confirmed that the dominant noise source is near the stabilizer. Since the acoustic pressure of the random pitch fan fluctuates according to the blade passin, the dominant BPF noise of the uniform pitch fan is modulated into some reduced discrete noises which have multiples of a 50Hz difference from BPF.

• 설비공학논문집
• /
• 제26권3호
• /
• pp.103-107
• /
• 2014

To assess a various of workplace noise environment in the tunnel construction site, the measurement is performed while tunnel constructing work. This study focuses on the sound attenuation according to the sound frequency characteristics and the distance from various works in the tunnel. Also, the noise distribution while blasting work is measured according to distance in this study. In addition, the boring processing, muck treatment, and tunnel lining by distance are measured for the noise distributions.

• 대한설비공학회지:설비저널
• /
• 제24권3호
• /
• pp.308-316
• /
• 1995