• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.522-528
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• 2001

This study was conducted to determine the sound paths and transmitted sound level in house. An air-conditioner system was selected a typical sound source. The measured transmission loss data shows that the apertures have an significant effect on the transmitted noise and comparable with the existing theoretical data. Therefore the complex aperture was substitute to quantitative apertures approximately. An effective simulation method, ray tracing and mirror image source method, was employed in the prediction of transmitted sound level. The measured results were reflected on the simulated results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.131-136
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the impact noise reduction methods. Reduction methods consist of four ways. First way is increase thickness of bare floor and other ways are using the soft coverings on the floor and ceiling assembles. Last way is make floating floor with shock absorbing materials.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.495-498
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• 2004

In the sound insulation measurements, the influence of background (extraneous) noise is often serious problem and how to reduce its effect and to improve the signal-to-noise(S/N) ratio is an important theme. As the background noise, such extraneous noises as road traffic noise and machine noise often disturb the measurement. In laboratory measurements on specimens with high sound insulation performances, even the internal noise of the measurement system can become a problem. To improve the signal-to-noise ratio and to improve the measurement accuracy, various kinds of digital signal processing techniques can be applied. In this paper, four kinds of digital signal processing techniques are applied and their effectiveness is examined by a simple sound insulation measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1018-1021
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• 2004

This study is an experimental study to introduce the soundscape design for urban parks. subjective response to soundscape for 4 urban park are carried out using 7 scale S.D. method which are included 25 adjective pairs. In order to recognized the effect environmental sound(bird singing, sweet environmental music, nature sound) for enriching the present sondscape, this study analyse the subject response for soundscape after and before using the environmental sound. The degree of satisfaction for visual atmosphere is higher than for auditory atmosphere of parks, this means that visual clues are much more effective to the environment condition than auditory clues. The effect of using the environmental sound is positive and effective to enrich the soundscape. On providing environmental sounds, it is necessary to consider the charcteristics of urban parks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1747-1751
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• 2000

It is well known that acoustic signals, even measured in an anechoic chamber, can be contaminated due to the wall interference. Therefore, it is necessary to reconstruct the original signal from the measured data, which is very critical for the case of measurement of source signal in a water tunnel. In this thesis, new methods for the reconstruction of sound sources are proposed and validated by using Boundary Element Method from measured data in a closed space. The inverse Helmholtz integral equation and its normal derivative are used for the reconstruction of sound sources in a closed space. An arbitrary Kirchhoff surface over the sources is proposed to solve the surface information instead of direct solution for the source. Although sound sources are not directly known by the inverse Helmholtz equation, the original sound source of pressure-field outside of the wall can be indirectly obtained by using this new method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.469-474
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• 2016

Abnormal sound was heard from a heat exchanger of condensate water system in a nuclear power plant, which was identified as impact sound of a loose part later. Nuclear power plants are normally equipped with loose part monitoring system for primary water system, but not for secondary water system. The abnormal sound was analyzed by using the impact signal-processing methodology based on the Hertz theory. The predicted results for impact location and size of the loose part showed good agreement with those of the actual loose part found during the overhaul period in the plant. So, this analysis methodology for the impact signal will be widely utilized for the primary and secondary side of the nuclear power plant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.719-724
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• 2013

In the case of newly developed stud which has more performance of sound transmission loss, it is expected that sound would transmit through runner than stud. so we developed construction method of runner and stud. As a result, sound transmission loss is improved about 2 dB by using this method. But this construction method could be applied to only newly developed stud. In addition, sound leak of wall joint is about 2 dB, and it could be improved by using rubber gasket at joint.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.792-796
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• 2003

In this paper, to detect external sound frequency on the latticed structure, fiber optic sensor net using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 50cm in width and 50cm in height, the optical fiber, 50m in length, distributed and fixed on the latticed structure. Single mode fiber, a laser with 1,550nm in wavelength, 2${\times}$2 coupler were used. External sound signal applied to the fiber optic sensor net and the detected optical signals were compared and analyzed to the detected microphone signals against time and frequency domain. Based on the experimental results, fiber optic sensor net using Sagnac interferometer detected external sound frequency, effectively. This system can be expanded to the structural health monitoring system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1244-1249
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• 2002

In this study, the physical characteristics of steel-wire sound absorbing materials with different thickness and bulk density is experimentally obtained in terms of the porosity and specific flow resistivity. Based on the experimental results, the following conclusions can be made. The porosities of steel-wire sound absorbing materials are smaller than those of general absorbing materials, which are inversely proportional to the volume densities. For the porosity measurement with a good accuracy, the dynamic correction based on the system compliance should be involved in porosity measurement. In addition, the flow condition for the precise measurement of the specific flow resistivity of steel-wire sound absorbing materials should be limited in the laminar flow region.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.579-585
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• 2002

This study has measured and evaluated the sound insulation of building elements of the hotel near airport. That measurement was made in both the actual site and laboratory. The differences of sound insulation performance in between granite and double glass were measured. Moreover, the difference of sound insulation was analyzed. For the measurement, this study has tried several methodologies, and analyzed the differences respectively. The results from this analysis were applied to produce a design guides for sound insulation to prevent external noise and to make more silent indoor space which satisfied the standard rate of noise.