• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.468-475
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• 2016

The purpose of this study is to investigate the acoustic problems of the conventional heat recovery ventilator and to suggest the methods of noise reduction from a heat recovery ventilator according to the installed location. The noise level, in this study, was measured and discussed as the parameters of size, wind volume and sound absorbing duct length for a heat recovery ventilator based on domestic and international related standards. It is found, as a result, that almost all of noise levels from the small and medium heat recovery ventilators without the sound absorbing duct in the anechoic chamber were higher than the noise standard value of 50 dB(A) regardless of the wind volume, and the noise levels went down when a sound absorbing duct was installed. In addition, the sound pressure level relative to frequency bands according to the length of sound absorbing duct was generally decreased, as the length of sound absorbing duct in the small and medium heat recovery ventilators was big, and the sound pressure level was generally increased, as the wind volume was great.

• Journal of Sasang Constitutional Medicine
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• v.10 no.1
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• pp.65-80
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• 1998

Proceeding an objective Study of sasang constitution diagnosis by Sound Analysis which uses Computed Sound lab(CSL), we verified the confidence level of Questionnaire of Sasang Constitution classification II(QSCC II) and the first results of Sound Analysis for verifying correlation between the physical character and Sound character are as follows. 1. The confidence level of QSCC II is 70.8% to Soeumin, 60.8% to Soyangin, 74.5% to Taeumin, and 70.08% in total. But, the actual results of verifying the confidence level after making 100 persons an object of study, are that the confidence level of that is 55.10% to Soeumin, 30.77% to Soyangin, 80.00% to Taeumin, and 55.29% in total. So it doesn't coincide with the confidence lecel of QSCC II 70.8%. 2. The results of verifying the confidence level about other 134 persons after enough explanation before the constitutional diagnosis by QSCC II are that the confidence of that is 71.08 to Soeumin, 54.76% to Soyangin 81.82% to Taeumin, and 69.22% in total. 3. The results of verifying the correlation between B.M.I. and Sasang Costitution are that there are significant differences below P<0.001 between Taeumin and Soeumin, and between Taeumin and Soyangin. 4. Height and Weight influence on a fundamental frequency and formant frequency. 5. There are differences for every constitutions in a amplitude when we nave a Sound analysis. As aboves, it is considered that we can find the differences among the constitutional groups, if we have a Sound analysis of the constitutional Sound characters.

• Journal of Biomedical Engineering Research
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• v.32 no.1
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• pp.55-60
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• 2011

Although sound intensity is considered as one of important factors in auditory processing, its neural mechanism in auditory neurons with limited dynamic range of firing rates is still unclear. In this study, we examined the effect of sound intensity adaptation on the change of glucose metabolism in a rat brain using [F-18] micro positron emission tomography (PET) neuroimaging technique. In the experiment, broadband white noise sound was given for 30 minutes after the [F-18]FDG injection in order to explore the functional adaptation of rat brain into the sound intensity levels. Nine rats were scanned with four different sound intensity levels: 40 dB, 60 dB, 80 dB, 100 dB sound pressure level (SPL) for four weeks. When glucose uptake during the adaptation of a high intensity sound level (100 dB SPL) was compared with that during adaptation to a low intensity level (40 dB SPL) in the experiment, the former induced a greater uptake at bilateral cochlear nucleus, superior olivary complexes and inferior colliculi in the auditory pathway. Expectedly, the metabolic activity in those areas linearly increased as the sound intensity level increased. In contrast, significant decrease interestingly occurred in the bilateral auditory cortices: The activities of auditory cortex proportionally decreased with higher sound intensities. It may reflect that the auditory cortex actively down-regulates neural activities when the sound gets louder.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.3
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• pp.91-96
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• 2014

For Sound source direction and separation method, Frequency Domain Binaural Model(FDBM) shows low computational cost and high performance for sound source separation. This method performs sound source orientation and separation by obtaining the Interaural Phase Difference(IPD) and Interaural Level Difference(ILD) in frequency domain. But the problem of reflection occurs in practical environment. To reduce this reflection, a method to simulate the sound localization of a direct sound, to detect the initial arriving sound, to check the direction of the sound, and to separate the sound is presented. Simulation results show that the direction is estimated to lie close within 10% from the sound source and, in the presence of the reflection, the level of the separation of the sound source is improved by higher Coherence and PESQ(Perceptual Evaluation of Speech Quality) and by lower directional damping than those of the existing FDBM. In case of no reflection, the degree of separation was low.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.186-189
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• 2005

Since human listening is very sensitive to sound, a subjective index of a sound quality is required. Therefore, in the analysis for each situation, the sound evaluation is composed with sound quality factor. Many researchers spends their effort to make a more reliable and more accurate of sound in term of sound quality index for various system noise. In this study a reliable index is constructed and analyzed using correlation analysis, regression analysis and weighting factor for each sound quality factor. We have made the sound quality index that agrees with more than human subjective sensitivity which apply to various sound quality metrics. Also we applied a 'grade' metric to jury for sound evaluation, analyzed relation between sound duality index and sound quality grade. Then we will judge the sound quality level according to the sound quality grade scheme.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.249-250
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• 2023

The objective of this study is to evaluate the airborne sound insulation performance between housing units and community facilities during the construction phase. Community facilities adjacent to housing units can lead to noise problems, hence it is necessary to minimize noise transmission during the design phase. However, flanking noise transmitted through gaps of structures, windows, pipes, and other openings may result in substandard sound insulation performance falling below the design standards. Therefore, It is crucial to measure airborne sound insulation in the field during the construction phase. The measurement was conducted using the survey method for the field measurement of the airborne sound insulation in accordance with KS F ISO 10052:2021. Although the noise standards caused by community facilities in apartment complexes are not specified in current laws and regulations, desired noise level was set based on international guidelines for indoor noise. First, the level of noise generated in community facilities was estimated, and then the sound insulation performance was evaluated to determine whether the desired noise level was achieved.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.36-43
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• 2004

In 1909 Hiram P. Maxim invented one of the first metal silencers for reducing sound levels in firearms. Silenced me have been mainly applied in the hunting and military operation. In particular special force make use of silenced rifle because it is low sound level. This paper considers experimental analysis for the characteristics of shock wave caused by shooting of a silenced me. Experimental results Indicate that the sound level of K-7 silenced rifle was lower than the sound level of MP5 silenced rifle. And, Sound Power Level of K-7 silenced rifle at a distance more than 75m or loom have nearly the constant value. This results that suggested the characteristics data about K-7 rifle's impulse noise will be apply to design the silencer of a small arms.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2003.11a
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• pp.73-76
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• 2003

This paper is contents about method to measure interception performance of shock noise of floor slab of apartment house to be simple. In the case of interception performance of light floor impact sound level, according to measurement method, grade of sound insulation performance showed greatly differently. But, in the case of interception performance of heavy floor impact sound level, it was similar result in all measurement method. Therefore, use of simple method of measurement was examined by possible fact in case of interception performance of heavy floor impact sound level.

• Journal of the Korean Wood Science and Technology
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• v.30 no.3
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• pp.75-84
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• 2002

In order to find out impact insulation properties, various types of current radiant floor heating systems and light-framed floors that are used in light-framed residential buildings were evaluated for two types of impact sources at the same time. Sound Pressure Level (SPL) was different from each impact sources for those spectrum patterns and peaks. In case of light-framed floor framework, the excitation position and the assumed effective vibrating area have effects on sound pressure level but it is not considerable, and Normalized SPL was reduced for each frequency by increasing the bending rigidity of joist. The mortar layer in the radiant heating system had relatively high density and high impedance, therefore, it distributed much of the impact power when it was excited, and reduced the Normalized SPL considerably. Nevertheless, Increasing a thickness of mortar layer had little influence on SPL. Ceiling components reduced the sound pressure level about 5~25 dB for each frequency. Namely, it had excellent sound insulation properties in a range from 200 to 4,000 Hz frequency for both heavy and lightweight impact sources. Also, there was a somewhat regular sound insulation pattern for each center frequency. The resilient channel reduced the SPL about 2~11 dB, irrelevant to impact source. Consequently, current radiant floor heating systems which were established in light-framed residential buildings have quite good impact sound insulation properties for both impact sources.

• Fire Science and Engineering
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• v.32 no.4
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• pp.42-49
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• 2018

In this study, in order to investigate whether or not the emergency broadcasting sound generated from an emergency broadcasting speaker is clearly transmitted to the occupant through architectural sound simulation, when the loudspeaker for emergency broadcasting is installed at intervals of 25 m according to NFSC 202 for a rectangular hallway. The sound pressure level and speech intelligibility index were analyzed according to changes in building finishing materials. With a reflective material finishing, sound pressure level satisfied the standard while speech intelligibility index was low. As a result of applying the sound absorbing material finishing, clarity and speech transmission index was improved to a level that could be understood by the occupant, whereas the sound pressure level delivered to the occupant decreased in the same space.