• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.923-929
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• 2017

Generally, the sound emitted from a vehicle powered by an electric motor is lower than that of internal combustion engine vehicles. Therefore, pedestrians often cannot detect approaching electric vehicles. Therefore, a certain additional warning sound is required for these types of automobiles. In this study, to develop an audible warning sound, nine warning sounds are designed based on signal processing and chord theory. The background noise measured on the road is also added to these synthetic sounds. The detectability of these warning sounds is evaluated by subjective tests. The sound metric is correlated to detectability and is investigated through psychoacoustic theory and subjective evaluation. It is determined that known psychoacoustic parameters such as loudness, sharpness, and roughness have a low correlation with detectability. However, it is found that the interval of harmonic sound correlates well with detectability.

• Science of Emotion and Sensibility
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• v.9 no.2
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• pp.133-140
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• 2006

In order to investigate the sensation of the fabric sound simulating the real wear-condition, the fabric sound simulator using reciprocating friction was developed. Fabric sounds from 5 specimen were generated by the fabric sound simulator and recorded using high performance microphone. Physical sound parameters of fabrics including level pressure of total sound (LPT), level range (${\Delta}L$), and frequency differences (${\Delta}f$) were calculated. For psychological evaluation, seven adjectives for sound (softness, loudness, sharpness, clearness, roughness, highness, and pleasantness) were used as the semantic differential scale. Fabric sounds by reciprocating friction of nylon taffeta and polyester leno had the highest value of LPT and evaluated as loud, sharp, rough, and unpleasant while polyester ultra suede and silk crepe de chine haying the lower LPT and ${\Delta}f$ were perceived as soft and quite. Comparing with fabric sound by one-way friction, fabric sound by reciprocation friction was perceived as more sharp, loud, and rough. LPT was also the most important factor affecting the sensation of the fabric sound by reciprocating friction.

• Science of Emotion and Sensibility
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• v.6 no.1
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• pp.27-32
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• 2003

The objectives of this study the effects of fabric noise from active wear on electrodiagnosis(EMG), to examine the effects on subjective sensation, and to relate the EMG results and the subjective sensation.. Five nylon water repellent taffeta fabrics were rubbed each other and the fabric noise were recorded. EMG was done from 10 female university students and electrodes were attached on each participant's upper arm and lower am. The subjective sensation was measured by FMME(Free Modulus Magnitude Estimation). The EMG values from upper arm showed higher voltage than those from lower arm, and the differences between values with fabric sound and without were larger at upper arm than those at lower am. EMG decreased when fabric sound was evaluated soft and pleasant, however It increased in proportion as fabric sound was evaluated loud and sharp. The predicted models for subjective sensation using physical sound properties and EMG results were well explained except roughness. Pleasantness was well predicted by EMG at upper am and EMG at lower arm, as the result, it was explained that the lower the EMG, the more pleasant the participant.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2003.05a
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• pp.1-4
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• 2003

본 연구는 경편성물의 특성에 영향을 미치는 중요한 구조변수인 조직, 편환의 계폐여부, 가이드바의 상호 움직임 방향에 따른 소리특성과 생리적 반응 사이의 관계를 파악함으로써 총합적 감성소재 설계를 위한 기초 자료를 제공하고자 하였다. 직물소리발생장치를 이용하여 7가지의 경편성물에 대한 마찰음을 녹음한 후, 이를 마찰음이 유발하는 생리반응을 측정하여 slow alpha파, fast beta파, ECG R-R, RESP, HF/LF, SCL, PV등을 분석하였다. 조직에 따라서는 LPT, Loundness(Z), Roughness(Z)와 Fluctuation strength(Z) 가장 큰 Sharkskin에서 fast beta파, ECG R-R, RESP는 증가하였으며 slow alpha파, PV, HF/LF는 감소하였다. 편환의 개폐여부에서는 폐환보다는 개환에서 Loudness(Z), Sharpness(Z), Fluctuation strength(Z)가 증가하였으며 RESP는 증가하고 HF/LF는 감소하여 개환이 더 불쾌한 감성을 유발하였다. 가이드바의 상호 움직임 방향은 counter보다는 parallel에서 slow alpha의 변화량이 감소하고 fast beta의 변화량이 증가하여 counter보다는 parallel이 더 불쾌한 감성을 유발하는 것으로 보인다. 또한 편성물의 음향특성 중 ΔL, Δf 와 Roughness(Z), Fluctuation Strength(Z)가 생리반응을 예측하는 중요한 요인으로써 나타났다.

• Journal of Sensor Science and Technology
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• v.25 no.3
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• pp.213-217
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• 2016

The superhydrophobic and superoleophobic meshes surfaces have been used in various applications such as self-cleaning, anti-icing, gas exchange, oil-water separation, sound-wave penetrable anti-wetting structures, etc. In particular, there are many studies for oil-water separation with environmental issues. Because of high pressure and dynamic environment, oil-water separation filters must have stable surface properties as super-hydrophobicity and superoleophobicity. The oleophobicity of surface depends on the surface chemistry and roughness of the surface. The roughness of oleophobic surface enhances its static contact angle and stability. The multi-scale hierarchical structure provides a stable superhydrophobic state by maintaining a Cassie state. In this research, we fabricated a superoleophobic mesh with a multi-scale hierarchical structure to increase the pressure resistance and adjusted a size of the mesh hole.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.56-62
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• 2003

The major noise source for the conventional train is the rolling noise caused by the interaction of the wheels and rails during the train passage on the tangent track. In order to control the rolling noise, the noise radiated from wheels, rails and sleepers should be analyzed and predicted. In this paper, a prediction method of wheel/rail rolling noise generated by the roughness of the wheel/rail surface is described, where the method is considering the effect of noise radiated by sleepers and the effect of ground. The method is applied to the Korean railway system, and the sound pressure level (SPL) predicted by the proposed method is compared with the measured SPL. Overall. the result shows good agreement between the predicted and measured values.

• International Journal of Railway
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• v.7 no.4
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• pp.109-116
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• 2014

For optimization of a low-noise track system, rail vibration and noise radiation needs to be investigated. The main influencing parameters for the noise radiation and the quantitative results of every track system can be obtained using a calculation model of generation and radiation of railway noise. This kind of model includes contact modeling and the calculation model of the dynamic properties of the wheel and the rail. This study used a nonlinear wheel/rail interaction model in the time domain to investigate the excitation of the rolling noise. Wheel/rail response is determined by time integrating Green's function of the rail together with force impulses from the wheel/rail contact. This model and the results of the study can be used for supporting calculation with the conventional model by an addition of the contributions due to nonlinearities to the roughness spectrum.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.163-171
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• 1999

The major source of railway noises is rolling noise caused by the interaction of the wheels and rails. This rolling noise is generated by the roughness of the wheel/rail surface on tangent tack in the absence of discontinuities, such as wheel flats or rail joints. These roughness cause relative vibrations of the wheel and rail at their contact area. The vibrations generated at the contact area are transmitted through the wheel and rail structures, exciting resonances of the wheel and travelling waves ill tile rail. Then these vibrations radiate noise to the wayside. In this paper, we predict the rolling noise radiated from radial/axial motion of the wheel and vertical/lateral motion of the rail using Remington's analytical model and then compare of the predicted sound pressure and measured one. Although there are some inaccuracy in our predication these results show in good agreement between 500 ㎐ and 3150㎐.

• ETRI Journal
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• v.35 no.5
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• pp.859-868
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• 2013

The active noise control (ANC) technique attenuates acoustic noise in a flexible and effective way. Traditional ANC design aims to minimize the residual noise energy, which is indiscriminative in the frequency domain. However, human hearing perception exhibits selective sensitivity for different frequency ranges. In this paper, we aim to improve the noise attenuation performance in perceptual perspective by incorporating noise weighting into ANC design. We also introduce psychoacoustic analysis to evaluate the sound quality of the residual noise by using a predictive pleasantness model, which combines four psychoacoustic parameters: loudness, sharpness, roughness, and tonality. Simulations on synthetic random noise and realistic noise show that our method improves the sound quality and that ITU-R 468 noise weighting even performs better than A-weighting.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.723-729
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• 2013

The contraction and expansion noise of a refrigerator are investigated, and some effective methods are proposed to reduce the level and occurrence frequency of noise. First, the noise of a refrigerator is measured to estimate the frequency spectrum and occurrence frequency of noise. Second, a sound visualization was conducted using an acoustic camera to determine the location of the noise source. From the results, it was observed that the internal part mainly producing noise was the third shelf in the freezer room. A method to estimate the acceleration on the location of the noise source is introduced to analyze the contraction and expansion noise precisely and accommodate experimental convenience. Noise reduction methods such as the replacement of the existing shelf with glass shelves, adoption of rail slides, and increase of roughness on the contact surface of the shelf are proposed and tested.