• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.521-525
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• 2011

It is known that the low-intensity sound stimulation really affect to grow the cell. The cellular growth mechanism, however, does not been clearly identified even the effect on the low-intensity sound stimulation. The purpose of this study is to investigate the effect of low-intensity sound stimulation on the alveolar UC-MSC proliferation. Before the low-intensity sound stimulation is applied, the UC-MSC are cultured for 24 hours to facilitate their attachments. The cells are divided into two groups. And each was exposed to a medium with or without the low-intensity ultrasound stimulation at 71dB intensity level. The UC-MSC are again divided into three treatment groups of group 1, 2, and 3 and exposed to a frequency at 50Hz, 100Hz, and 1000Hz, respectively. In the results, it is investigated that the growth rates of UC-MSC for the stimulated groups were higher than those of control groups. In 1000Hz frequency, the number of UC-MSC cell is significantly higher than control groups (p>0.05). We would put the hypothesis that the cell growth could be enhanced by an appropriate low-intensity sound stimulation.

• International Journal of Highway Engineering
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• v.18 no.5
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• pp.49-56
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• 2016

PURPOSES : In this study, noise reduction effect of a two-layer porous asphalt pavement was investigated through site measurement and computer simulation. METHODS : To examine noise reduction effect, a 3 km long quiet pavement was installed by removing previous normal pavement, which had a rather low porosity. The studied site was a high-rise apartment building surrounded by the quiet pavement and Seoul ring road with heavy traffic volume, indicating relatively high background noise. RESULTS : The measurement result before and after installing the quiet pavement showed a noise reduction effect of 4.3 dB(A) at a distance of 7.5 m from the road. After validating the accuracy of simulation using SoundPLAN, the reduction in SPL(sound pressure level) at the facades by the quiet pavement was predicted by considering five different road conditions generating traffic noise from each road or in the combination of the quiet pavement and Seoul ring road. In the case of no noise from Seoul ring road, noise reduction at the facades was 4.2 dB(A) on average for 702 housing units. With background noise from Seoul ring road, however, the average SPL decreased to 2.0 dB(A). Regarding subjective response of noise, the number of housing units with a noise reduction of over 3 dB(A) was 229 out of 706 units (approximately 32%). For 77 housing units, the noise reduction was between 1~3 dB(A), while it was less than 1 dB(A) for 400 housing units. CONCLUSIONS : The overall result indicates that the quiet pavement is useful to reduce noise evenly at low and high floors compared to noise barriers, especially in the urban situation where background noise is low.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.1
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• pp.1-6
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• 1975

The sea noise of moving trawl net was recorded by an underwater tape recorder which was set wireless, and was analyzed by a sound level meter and an octave-band analyzer. The frequency distribution of sea noise of the moving otter trawl net ranged from DC to 5000 Hz, and the dominant frequency zone ranged from 500 Hz to 700 Hz, and the maximum sound pressure is about 22 dB at the otter trawl net. The main sound source of the sea noise from the moving trawl net was found to be sea noise due to the resistance of the ground rope against the sea bottom.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.456-462
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• 2013

Eco-friendly material applied to building would be one of the materials which is must developed for global environmental conservation and reduction of carbon dioxide. For development of eco-friendly material, a cellulose absorber has been developed with waste paper through adjustment of various mix proportions. The developed cellulose absorber has been tested for its acoustic properties such as absorption coefficient and dynamic stiffness. The absorption coefficient was evaluated by developing six samples and using impedance tube and reverberation chamber. As a result of the evaluation, 0.64(NRC) was secured in absorption coefficient and 4.7 $MN/m^3$ was indicated in dynamic stiffness. Also, for practical use of developed absorbers as inner heartwood in drywall, comparison test of sound reduction index was performed with existing glass wool absorbers and constructed drywall of gypsum board. The results have shown 55 dB(Rw) of sound reduction index in glass-wool wall and 46 dB(Rw) in cellulose.

• Journal of the Korean Society of Radiology
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• v.12 no.4
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• pp.491-496
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• 2018

The purpose of this study is to analyze the noise spectra in DWI (diffusion-weighted imaging) pulse sequences of 1.5 Tesla and 3.0 Tesla MRI, The ACR (American College of Radiology) phantom and noise spectrum were analyzed by FFT (fast Fourier transform) and TFFT (temporal frequency analysis) using WavePad sound editor version 8.13 (NCH software, Greenwood Village, CO, USA). Noise spectra, FFT and TFFT were analyzed for laboratory 1.5Tesla and 3.0Tesla DWI MR pulse sequences. The noise threshold of the frequency amplitude in the FFT and TFFT at 3.0Tesla compared to 1.5Tesla was between 1.5Tesla and -6 dB, and between 3.0Tesla and 0 dB, the DWI pulse sequence for the patient's noise reduction was appropriately MR examination needs to be applied.

• Journal of ILASS-Korea
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• v.18 no.3
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.22-30
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• 2005

We implement an interactive 3D audio broadcasting terminal which synthesizes an audio scene according to the request of a user. Audio scene structure is described by the MPEG-4 AudioBIFS specifications. The user updates scene attributes and the terminal synthesizes the corresponding sound images in the 3D space. The terminal supports the MPEG-4 Audio top nodes and some visual nodes. Instead of using sensor nodes and route elements, we predefine node type-specific user interfaces to support BIFS commands for field replacement. We employ sound spatialization, directivity/shape modeling, and reverberation effects for 3D audio rendering and realistic feedback to user inputs. We also introduce a virtual concert program as an application scenario of the interactive broadcasting terminal.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.15 no.4
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• pp.239-252
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• 1993

This study was done to analyze phonetic dysfunction and the effect of orthognathic surgery to phonation in the patients of mandibular prognathism. 20 persons were chosen as normal group and 20 patients of mandibular prognathism as abnormal for this study. 5 vowel sounds-'ㅏ(a)', 'ㅔ(e)', 'ㅣ(i)', 'ㅗ(o)', 'ㅜ(u)' and 14 consonant sounds-'ㄱ(g)', "ㄴ(n), 'ㄷ(d)', 'ㄹ(l)', 'ㅁ(m)', 'ㅂ(b)', 'ㅅ(s)', 'ㅇ(ng)', 'ㅈ(j)', 'ㅊ(ch)', 'ㅋ(k)', 'ㅌ(t)', 'ㅍ(p)', 'ㅎ(h)', were checked. We recorded these sounds in the period of preopration, postop. 12 months, postop. 24 months. A Formant ratio and a length of consonant time were studied with discriminant analysis. As a result of the study, the following conclusion were gained. 1. As a result of the analysis on vowel dysfunction patiensts of mandibular prognathism, more than 80% of men patients showed the dysfunction in prelingual sound 'ㅔ(e)' and 'ㅣ(i)'. More than 70% of women patients showed the dysfunction in all vowel. 2. One year later from the orthognathic surgery, men patients showed a marked improvement in 'ㅏ(a)'. The next were 'ㅗ(o)', 'ㅜ(u)' and 'ㅣ(i)'. Women patients showed a marked improvement in 'ㅜ(u)'. 3. Two year later from the orthognathic surgery, men patients showed a marked improvement in prelingual sound 'ㅔ(e)' and postlingual sound 'ㅗ(o)'. Women patients showed a marked improvement in 'ㅏ(a)'. More than 20% of patients showed the phonetic improvement compared with the condition of the postop. 12 months. 4. As a result of the analysis on consonant dysfunction patient of mandibular prognathism. more than 80% of men patients showed the dysfunction in lingual sound 'ㅅ(s)'. Most women patients showed the dysfunction in labial sound 'ㅁ(m)' and lingual sound 'ㄴ(n)'. More than 50% of patients showed the dysfunction in labial sound and lingual sound. 5. One year later from the orthognathic surgery. men patients showed a complete improvement in hard palatal sound 'ㅈ(j)'. The next were labial sound 'ㅂ(b)', lingual sound 'ㅅ(s)', soft palatal sound 'ㄱ(g)' and 'ㅋ(k)'. Women patients showed a marked improvement in soft palatal sound 'ㅇ(ng)' and 'ㄱ(g)'. 6. Two year later from the orthognathic surgery, all patients showed remarkable improvement in consonant sounds. except for labial sound 'ㅁ(m)', 'ㅍ(p)' and lingual sound 'ㄴ(n)'. The improvement ratio was increased as the time was going on compared with the condition of postop 12 months.

• International Journal of Fluid Machinery and Systems
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• v.7 no.1
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• pp.7-15
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• 2014

In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.101-104
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• 2005

This study presents experimental results from the performance test of a scaled reverberation chamber for measurement of sound insulation of panels. Experimental investigations were conducted in various parameters such as tunneling effect source locations, and maximum sound transmission loss. It is evident that the tunneling effect which means the variation with specimen location on the test frame gives rise to more than 3 dB deviation. One of the objective of this study that compares measured results between a real reverberation chamber and a simplified test apparatus, by using a specimen of a sandwich panel. It shows qualitatively resonable agreement from which one can find a potential to provide a design tool.