In this study, the noise reduction effect of the steam vent silencer was investigated by performing a transient flow analysis applying the Loss Model, a porous flow analysis model, and calculating the noise intensity from the pressure fluctuation according to the time change. As a result of flow analysis, it was confirmed that the noise intensity decreased as the number of diffusers and the number of splitters made of foamed aluminum increased. In the case of three-stage diffusers, the noise intensity decreased by up to 33.4 dB when six foamed aluminum with a thickness of 150mm were installed.

There are many disadvantages to existing silencers used in power plants. Recently, high-performance silencers are required in society, so it is necessary to develop silencers accordingly. Therefore, in this study, to develop the flow silencer by taking advantage of the foamed aluminum, the property values such as loss coefficient and porosity were obtained through experiments, based on the Forchheimer's law. CFD analysis was performed by applying a porous modeling technique to foamed aluminum and the results were compared with experimental values. The error rate between the results of the experiment and the flow analysis is within about 2.79%, so the results of the experiment and the analysis agree relatively well. When the foamed aluminum was installed, the flow noise was reduced by about 5.14dB.

High power trends in the diesel engines due to engine downsizing do not provide noise attenuation that can be satisfied with the performance of the existing silencer on account of high frequency increases in the exhaust noise. This study improves the attenuation performance of the exhaust silencer of the diesel engine and suggests silencer structure that performs best attenuation performance, especially at the high frequency range in the exhaust noise. It proposes dual silencer structure with an average attenuation performance of 6.4 dB and a maximum of 10.7 dB in the high frequency range (over 500 Hz), and analyzes its characteristics compared with the existing silencer. The performance analysis is performed according to 'Measurements on silencers in situation–ISO 11820:1996 Acoustics' and describes the results of comparative analysis with the existing silencer.

Based on the attitude of science discovery, an industrial induction motor silencer is designed and developed, and the performance of this silencer is evaluated experimentally in this paper. The basic principle of the silencer was used as the parabola principle. During the experiment, the performance of the proposed silencer is preliminary researched using software simulation method, test analogy method, and some other methods to infer experiment was conducted to evaluate the experiment. During the simulation experiment, 25dB level can be reduced in the 12,500∼16,000Hz range. More than 35dB level was reduced in the 2,500∼5,000Hz range. When we used the silencer, the noise in the high frequency bands above 1,000Hz are reduced. In particular, 1,600Hz band is greatly reduced on average by 5dB. Some effective conclusions are obtained from the analysis of the experiment results, despite some uncertain factors in the experiment

The object of this paper is to examine the noise generating mechanism at manufacturing process of metal material products. To accomplish the object; A noise generating mechanism of high noise machine, which is mounted in the small and medium size enterprise, was investigated. The measurement method of the noise for the machine by manufacturers were investigated. The noise at the 250 point of the manufacturing procrss machine in the 40 processes of the 3 factories, 3 business fields was measured. The database of the noise was built from the measurement data. The major sound sources and frequency range for the manufacturing processes of metal product machine was investigated.