• The Journal of the Acoustical Society of Korea
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• v.4 no.1
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• pp.35-42
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• 1985

This paper suggests a method on the use of very long linear array microphone in order to obtain clear loud sound reinforcement system without howling. According to the results of the theoretical investigation, we have made that a linear array microphone. This is made of one hundred small condenser microphone having 2 cm of spatical period. To estimate the effect of sound reinforcement system physically and subjectively, four cases have been experimented : In case of using no sound reinforcement, nondirectivity microphone, rectangular window and Hnning window in linear array microphone. The experimental results prove that the case of Hnning window in linear array microphone is more excellent.

• The Journal of the Acoustical Society of Korea
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• v.30 no.8
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• pp.468-473
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• 2011

Speech may not be clearly understandable in the room that is highly reverberant, due to the loss of consonants intelligibility. Therefore, it is very important to obtain a high sound pressure level of direct sound in reverberant room. A properly designed sound reinforcement system can not provide the good speech intelligibility without the absorption treatments of walls. With using the highly directional speaker, we can transmit the sound energy into only the areas where people are sitting. This can be help to improve the speech intelligibility. In this paper, even in reverberant rooms, it will be shown that the good speech intelligibility can be obtained by only the directivity control of speaker without the room treatment. Also, it would be more improved by the properly room tuning using an equalizer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.383-386
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• 2005

Low frequency heavy-weight impact noise is the most irritating noise in Korean high-rise reinforced concrete apartment buildings. This low frequency noise is generated by foot traffic due to the fact that Koreans do not wear shoes at home. The transmission of the noise is facilitated by a load bearing wall structural system without beams and columns which is used in these buildings. In order to control low frequency heavy-weight impact noise, floating floors using isolation materials such as glass-wool mat and poly-urethane mat are used. However, it was difficult to control low frequency heavy-weight impact sound using isolation material. In this study, reinforcement of concrete slab using beams and plate was conducted. Using the FEM analysis, the effect of concrete slab reinforcement using FRP(fiber-glass reinforced plastic) on the bang machine impact vibration acceleration level and sound were conducted at the standard floor impact sound test building. The $3{\sim}4dB$ floor impact vibration acceleration level and impact sound pressure level were reduced and the natural frequency of slabs were changed.

• KIEAE Journal
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• v.2 no.1
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• pp.41-48
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• 2002

This study aims to investigate and evaluate the room acoustic designs of a multi purpose gymnasiums which do not use adjustable treatments in order to change the acoustical characteristics. Considering the main uses of gymnasium and auditorium, experiments were carried out using both nondirectional speakers on the stage and loudspeaker installed on the ceiling. The result from the study are as follows; Measured RT under unoccupied condition was a little longer than the expected value, therefore, in the case of occupied condition RT would be close to the optimum value. However, parameters that evaluate intelligibility and speech transmission property appeared to be low and have large differences depending on the measuring points, therefore, more effective sound reflecting surfaces and sound reinforcement systems should be considered.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.67-75
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• 2011

The present work investigate the effect of sound reinforcement systems on the acoustics of a large dome stadium using a computer simulation. The acoustics of a dome stadium was predicted analyzed by varying room absorption, as well as the configuration of speakers including their directivity, installed height, and numbers. It was found that both D50 and RASTI were improved by increasing room absorption. Larger EDTs were observed according to the increase of room absorption at mid and high frequencies. On the other hand, RT did not show any significant correlation with the changes in room absorption, which might be the effect of a forced linear fitting for non -linear energy decay process. With respect to the speaker configuration, the speech intelligibility of a sound reforcement system installed at higher placed more relied upon their directivity rather than room absorption, Also, lower placing of speakers was found to be effective in decreasing RTs regardless of room absorption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.796-799
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• 2005

In 2005, a regulation on the heavy-weight impact sound was released, which restricted concrete slab thickness of standard floor to 210mm. To reduce heavy-weight impact sound, damping materials and structural reinforcement system have been proposed. In this study, the effect of compressive strength on the heavy-weight impact vibration and sound were investigated. FEM analysis was conducted for the 34PY apartment with different concrete strength (210, 350, 420kg/cm$^2$). In addition, apartment floors with different concrete strength were constructed and the floor impact vibration and sound were measured. Results of FEM analysis and measurement show that the resonance frequency of concrete slab was increased by the increment of concrete strength. However, floor impact sound pressure level did not decrease because the nor impact vibration and sound pressure level in 63Hz band increased.

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.431-444
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• 2012

Constituents of timber framed floor affect the insulation performance against impact sound significantly. Among them, installation of massive sound absorbing layer and reinforcement of stiffness of timber floor have been considered as major factors that improve the insulation performance against impact sound. Researches on evaluating the effect of floor constitutions have been carried out through the field measurements for timber framed buildings in Korea. It is concluded that the impact sound pressure level at the relatively lower frequency governs the overall insulation performance, and can be improved by the installation of sound absorbing layer and reinforcement of floor stiffness. Especially, the insulation performance against heavy impact sound was improved significantly when the massive cement mortar layer for floor heating system was installed and the stiffness was reinforced by shortening the joist span using additional beam at the mid-position of original span.

• KIEAE Journal
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• v.9 no.2
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• pp.99-106
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• 2009

The noise in apartment buildings are major factor that determine the quality of indoor noise environment. Particularly, the noise from children's running footsteps and plumbing noise have caused the residents who live in decrepit apartment houses to uncomfortable environment. And as time go by, sound performance are getting worse according to the aging of the facilities. So this study deals with the plans to improve the sound performance of decrepit apartment house. To compare the noise reduction, we measured the heavy-weight impact sound level and plumbing noise level before and after changes the measurement conditions. As the results of measurements, the heavy-weight impact sound level were decreased when stiffness reinforcement were installed on slab. Especially the sound level were decreased 2.1-7.6dB in 50-80Hz of low frequency range. Instead of PVC pipe system, cast iron pipe and triple elbow drain pipe systems were installed. Noise level were decreased 15dB(A) in 250Hz. Noise level of pipe system's on the slab is less than under slab one. On the contrary water saving stool showed increasing the noise level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.462-467
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• 2000

The aim of this study is to provide fundamental data for acoustic design by analyzing the room acoustic characteristics according to the PA system used in the school gymnasium. The measurements were carried out accordance with the ISO 3382. The sources used in this study were four types; omni-directional, centralized, distribution, the combination of centralized and distribution sound source system. Omni-directional system is recommended by ISO for the acoustic test and the others are installed on the wall, column and ceiling in the school gymnasium for sound reinforcement.

• The Journal of Fisheries Business Administration
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• v.39 no.3
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• pp.111-137
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• 2008

Fisheries resources living in inland have continuously reduced due to over-fishing and development thoughtless for the environment. Inland fisheries that target the fisheries resources have been also confronted by several problems such as insufficiency of inland fisheries management systems, inconsistent fisheries management system, inferior infrastructure of inland fisheries, and decreasing fishermen's real income. These problems have demotivated fishermen who want to focus on fishing and farming activation. Therefore, this paper provides alternatives of reorganization for turning to sound and healthy inland fisheries industries by reviewing Korean inland fisheries management systems. The reorganization should be preferentially granted resource management by water system considering geographical conditions, seed release, and establishment of fisheries order for maintenance of sound and healthy inland fisheries. Also, the reorganization should be moved toward the competitive strengthening of "company unit" for inland fisheries, the nourishment of fisher-oriented fisheries management system, strong relationship among inland fishermen, the systematic management of inland fisheries, the strengthening of guidance service for inland fisheries, the extension of infrastructure related to fisheries production, the development of inland fisheries policy including public people, and the improvement of inland fisheries system and law reflecting various users of inland fisheries.