• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.81-84
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• 2007

In this paper, fiber optic sound and vibration monitoring sensor which is latticed shape structure based on Sagnac interferometer is fabricated and tested in laboratory conditions. To detect external vibrations surface mounted fibers on the latticed steel wire fence with a dimension of 170cm by 180cm is used. To detect external sound frequency the tightened fiber optic itself wire netting fence with a dimension of 50cm by 50cm is used. Experiments for the detection of the excited vibration and sound signals were performed. A small vibrator induced external vibration signal and it is applied to the latticed structure in the range of 100Hz to several kHz. External sound signal applied to the fiber optic sensor net using non-directional sound speaker. The detected optical signals were compared and analyzed to the detected both accelerometer and microphone signals in the time and frequency domain. Based on the experimental results, distributed fiber optic sensor using Sagnac interferometer detected effectively external vibration and sound signal and had a good performance. This system can be expanded to the monitoring of a significant system and to the structural health monitoring system.

• 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.569-576
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• 2004

In this paper, to detect external sound frequencies on the latticed structure, fiber optic sensor net using Sagnac interferometer was fabricated and tested. The latticed structure was fabricated with a dimension of 50 cm in width and 50 cm in height. The optical fiber of 50m in length was distributed and fixed on the surface of the latticed structure. Single mode fiber, a laser with 1,550 nm in wavelength, 2 ${\times}$ 2 coupler were used. External sound signal, 240 Hz, 495 Hz, 1.445 kHz, 2k Hz, applied to the fiber optic sensor net and the detected optical signals were compared to the detected microphone signals against time and frequency domains. 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.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.621-628
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• 2022

The most realistic way to reduce noise outside the building, such as road traffic noise and aircraft noise, is to strengthen the sound insulation performance at the sound collecting points such as balconies, windows, and exterior walls of each building. However, in light of the reality that shading devices outside buildings are not yet widely used, there are not many studies on sound insulation performance improvement using external windows and window devices such as louvers and blinds. In particular, external blinds can not only block the inflow of strong sunlight in the morning and evening from the outside of the building, but also target the sound insulation effect that blocks the peak noise that occurs during commuting hours. In this study, a study was conducted to improve sound insulation performance against external noise by using an external electric blind (EEB), which is one of the most efficient window and door external shading devices. Various sound insulation performance tests were conducted while changing the configuration of external electric blinds developed for light blocking purposes. Through this, it was verified that an additional sound insulation performance of 6 dB can be obtained by installing an external electric blind compared to the reduction performance of general windows.

• Journal of the Korean housing association
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• v.10 no.2
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• pp.203-212
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• 1999

The purpose of this study is to evaluate the Korean residents' subjective opinion of the noise on the lowrise multifamily house in America. The results of this study can be applied for the prevention of noise when planning cities, roads, and multifamily houses in Korea. The subjects of this study are three kinds of multifamily houses and their 124 Korean residents in Athens, America. The results of this study are as follows. The Korean residents felt the noise from lawn mowers and the sound of filter fan of air conditioners were higher than all the other external noise. They were disturbed a little by the external noise. The air borne sound was recognized a little by Korean residents but they only felt moderate sound of building services and household equipment from the solid borne sound of the internal noise. They suffered worse from external noise in the summer and they felt worse from 8～12 o'clock due to external noise and 20～24 o'clock due to internal noise. The Korean residents liked the sound of birds or insects, the sound of cars and trains. However many Korean people in Athens disliked the sounds of birds or insects and lawn mowers more than these sounds in Korea. The Korean residents who were living in the apartment houses felt better than those in the other multifamily houses.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.698-704
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• 2022

In this paper, the radiated aerodynamic noise generated from sound sources of a nozzle inflow is quantitatively investigated and compared with experimental results of externally radiated noise. A high-resolution unsteady compressible Large Eddy Simulation (LES) technique is used to accurately predict the internal and external flow of three types of nozzle shape. Through using the vortex sound source for sound sources, the geometry of nozzle neck is identified as most significant aerodynamic noise sources. For validation of quantitative analysis, the vortex sound source intensity of internal nozzle flow is compared with results of external radiated noise of calculation and experiment.

• Korean Journal of Human Ecology
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• v.1 no.2
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• pp.61-74
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• 1998

The purpose of this study is to investigate residents subjective opinion of the noise on the low-rise multifamily house in U.S.A. The results of this study can be applied for the prevention of noise when planning cities, roads, and multifamily houses in Korea. The subjects of this study are three kinds of multifamily houses and their 109 residents in Athens, U.S.A. The results of this study are as follows. The residents felt the noise from lawn mowers and the sound from filter fans of air conditioners were higher than in the other external noise. The residents daily activities were disturbed a little by the external noise. Of the internal noise, the air home sound was recognized a little by residents. They only felt a moderate sound level from the building services of the solid borne sound. They suffered worse from noise in the summer and they felt worse from 16∼20 o'clock due to noise. The residents who were living in town houses felt better than those in the other multifamily houses. (Korean J Human Ecology 1(2):61∼74. 1998)

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.181-188
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• 2023

In a typical living space, windows are directly exposed to the external noise environment. The best way to reduce outside noise is to block it from the outside, not the inside. Exterior blinds for blocking sunlight are commercialized in various ways. However, it has not yet been actively utilized in Korea. In the previous study, an experiment was conducted in an accredited laboratory to verify the sound insulation performance of an external motorized blind manufactured for shading. And it was verified that there is a sound insulation performance of 6 dBA compared to the reduction performance of a general window. In this study, we tried to confirm the reduction performance by applying the sound insulation performance of external electric blinds to windows in actual living spaces. In addition, an improvement plan was sought to increase the effective noise reduction performance. As a result of the measurement, the reduction performance of the external motorized blind itself was insufficient at the level of 1 dBA to 3 dBA. However, additional reduction performance of the 2 dBA level was confirmed by filling the gap between the blind slits.

• Journal of KSNVE
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• v.7 no.3
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• pp.427-437
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• 1997

Mean active intensity based active control for the cancellation of radiated noise out of the duct exit is studied. The active intensity control strategy is drerived based on the relation of the exterior sound field out of the duct termination and interior sound field of the duct. One of the characteristics of this control strategy is that the control performance can be maintained regardless of the sensor loction, compared with the conventional local pressure control methods at either interior downstream or exterior field positions. It is also suggested that the digital filtering for the active intensity control can be achieved by time-domain filtered-x LMP (Lest-Mean-Product) adaptive algorithm. Experiments for an open-ended duct are performed to compare the active intensity control performance with conventional pressure control one. Active control experiment of local sound pressure is conducted by widely used filtered-x LMS adaptive Algorithm and active intensity control implementaion uses the derived filter d-x LMP algorithm. It is shown that the exterior sound fileds was much better observable by sensing of the active intensity than by just sound pressure. It is also demonstrated that the global control performance of external field by acoustic intensity is superior to the conventional sound pressure control performance.

• Speech Sciences
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• v.7 no.4
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• pp.83-90
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• 2000

The purpose of this study was to examine some acoustic characteristics in the ear canal. It was assumed that a sound outside the external auditory canal could be different from the sound inside the external auditory canal. The acoustic signals were captured by a probe microphone placed at a distance within 1 cm from the tympanic membrane, and a reference microphone was placed over the upper pinna. Three vowels /a/, /i/, /u/ were recorded from a normal adult male speaker. The parameters such as the formant frequency ($Fl\simF5$) and the peak intensity were measured using a speech analyser, PCquirer. It was found that the entering part of the external auditory canal functions as a narrowing point as to the speech that passes through the free field. Results show that acoustic characteristics were changed for speech discrimination rather than speech perception.