• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.681-686
• /
• 1997

Foamed aluminum is well known metallic porous sound absorption material which has excellent properties of light weight and high absorbing performance. For the purpose of finding out the sound field characteristics within a simple closed cubic enclosure with foamed aluminum, analytic and experimental studies are performed. For the first time, the standing wave apparatus is used to measure absorption coefficient and impedance of the foamed aluminum. Next, the sound effects of absorption material in acoustically loaded rectangular enclosure are identified according as the foamed aluminim is to be or not.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.6
• /
• pp.413-419
• /
• 2002

Noise barriers are widely used to reduce the sound level propagating from highways, railways or factories to residential areas. The reduced noise level at a receiver point is then determined by the diffracted waves around the edge of the barrier as well as by the transmitted waves through the barrier. 1'or proper usage, many studies either theoretical or experimental have been made with the objective of precisely Predicting the acoustic field and improving the noise attenuating properties of barriers. In this study. a simple scattering model. a line acoustic source scattered by an infinite cylinder, is introduced to simply Investigate the sound attenuation efficiency of a sound-resonating barrier. From this model study, it is observed that the sound-resonating harrier can be used as a good sound-shielding element especially for the pure-tone noise generated from the transformer. Large sound-attenuation is achieved by applying the sound-resonating barrier to the large transformers in a substation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.618-621
• /
• 2014

This research is to review the possibility of reducing the noise radiated from the tube exit by controling the sound reflection coefficient at the inclined exit. The sound reflection coefficient at the inclined exit of flanged tube was measured by both transfer function method and standing wave ratio method. Accuracy on the sound reflection coefficient measured by transfer function method was verified through comparison with sound reflection coefficient measured by standing ratio method. The flanged tube had lower sound reflection coefficient than the tube which have no flange. Also the sound reflection coefficient was decreased in accordance with increasing the inclined angle of unflanged tube.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.659-664
• /
• 2001

Noise barriers are widely used to reduce the sound level propagating from highways, railways or factories to residential areas. The reduced noise level at a receiver point is then determined by the diffracted waves around the edge of the barrier as well as by the transmitted waves through the barrier. For proper usage, many studies either theoretical or experimental have been made with the objective of precisely predicting the acoustic field and improving the noise attenuating properties of barriers. In this study, a simple scattering model, a line acoustic source scattered by an infinite cylinder, is introduced to simply investigate the sound attenuation efficiency of a sound-resonating barrier. From this model study, it is observed that the sound-resonating barrier can be used as a good sound-shielding element especially for the pure-tone noise generated from the transformer. Large sound-attenuation is achieved by applying the sound-resonating barrier to the large transformers in a substation.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.1
• /
• pp.22-28
• /
• 2012

While a dash panel component, close to passengers, plays a very important role to protect heat and noise from a power train, it is also a main path that transfers vibration energy and eventually radiates acoustic noise into the cavity. Therefore, it is important to provide optimal design schemes incorporating sound packages such as a dash isolation pad and a floor carpet, as well as structures. The present study is the extension of the previous investigation how design variables affect sound radiation, which was carried out using the simple plate and framed system. A novel FE-SEA hybrid simulation model is used for this study. The system taken into account is a dash panel component of a sedan vehicle, which includes front pillars, front side members, a dash panel and corresponding sound packages. Design variables such as panel thicknesses and sound packages are investigated how they are related to two main NVH indexes, sound radiation power(i.e. structure-borne) and sound transmission loss(i.e. air borne). In the viewpoint of obtaining better NVH performance, it is shown that these two indexes do not always result in same tendencies of improvement, which suggests that they should be dealt with independently and are also dependent on frequency regions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.979-982
• /
• 2007

The effect of a scattering wall surfaces on sound diffusion can be assessed by determining the scattering and diffusion coefficients in the laboratory. However, the sound field in a concert hall including scattered reflections is different from the laboratory measurement condition. Therefore, there is a need for objective investigation of diffusion in real sound fields. In this paper, possible acoustical parameters of in-situ measurements are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.692-693
• /
• 2004

We introduce a new velocity sensor, micro-flown sensor, which was developed by H-E de Bree. The sound absorption coefficients of a fiber material with the conventional pressure microphones and the micro-flown sensors were measured and compared. The experimental results show that both sensors could be well applied to measure the sound absorption coefficient but the pressure sensor was rather stable than micro-flown sensor

• Journal of KSNVE
• /
• v.6 no.6
• /
• pp.781-790
• /
• 1996

The goal of current research is to suppress the acoustic noise radiated from vibration of composite plate structure. The induced noise can be reduced through the control of the corresponding structural vibration modes by using the piezoelectric materials as actuator. The acoustic fields are to be analyzed through the boundary element method (BEM) based on the Rayleigh intergral equation and structural system through the finite element method (FEM). The suppression of rediated sound is studied by adaping the piezoelectric material as the distributed actuator. Numerical results are presented on the sound radiation from composite plate of arbitrary boundary conditions, the noise reduction adapting the piezoelectric materials as distributed actuator. The results show the effectiveness and possibility of piezoelectric actuator in the control of sound radiation from composite structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.5 s.98
• /
• pp.558-563
• /
• 2005

This research aims to derive the general emotion and preference of the 25 sounds by using the questionnaire method to provide the contents for the soundscape design fit to the characteristics of the given situation. The results can be summarized as follows : Nature sounds except dog barking and locust crying showed highest preference, and the traffic sounds, baby crying and footstep of upper floor showed the lowest. Hereby, the sound recognition can be different each other according to quality of tone and situation even they are the same sounds. The most impressive, wanted to be conserved and retrospective sound was the nature sound, and the most wanted to be removed sound was the machinery sound. And the social sound was shown as the most korean and fit to the art theme street.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.806-809
• /
• 2004

This research aims to derive the general emotion and preference of the 25 sounds by using the questionnaire method to provide the contents for the soundscape design fit to the characteristics of the given situation. The results can be summarized as follows; Nature sounds except dog barking and locust crying showed highest preference, and the traffic sounds, baby crying and footstep of upper floor showed the lowest. Hereby, the sound recognition can be different each other according to quality of tone and situation even they are the same sounds. The most impressive, wanted to be conserved and retrospective sound was the nature sound, and the most wanted to be removed sound was the machinery sound. And the social sound was shown as the most korean and fit to the art theme street.