• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.452-459
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• 1997

For computer aided design and construction of low noisy power plants, indoor and outdoor noise prediction program has been developed. The program utilizes the predefined data of noise sources and building materials and has the faculty to estimate the source level using the empirical formula in case of the measured data not being available. In the noise prediction, the mutual noise propagation between indoor and outdoor sites are considered. The outdoor noise source in the calculation of geometric divergence effects is modelled as the omni-directional finite line or planar source according to the source geometry and the receiving points. Outdoor noise prediction is carried out to consider the diffraction effect due to plant structures as well as the attenuation effect due to atmospheric absorption and soft ground. The results of indoor and outdoor noise prediction for a recently constructed diesel engine power plant show good agreement with the measured.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.4
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• pp.374-385
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• 2012

The indoor noise of a ship is usually determined using the A-weighted sound pressure level. However, in order to better understand this phenomenon, evaluation parameters that more accurately reflect the human sense of hearing are required. To find the level of the satisfaction index of the noise inside a naval vessel such as "Loudness" and "Annoyance", psycho-acoustic evaluation of various sound recordings from the naval vessel was performed in a laboratory. The objective of this paper is to develop a single index of "Loudness" and "Annoyance" for noise inside a naval vessel according to a psycho-acoustic evaluation by using psychological responses such as Noise Rating (NR), Noise Criterion (NC), Room Criterion (RC), Preferred Speech Interference Level (PSIL) and loudness level. Additionally, in order to determine a single index of satisfaction for noise such as "Loudness" and "Annoyance", with respect to a human's sense of hearing, a back-propagation neural network is applied.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.982-986
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• 2013

The noise emitted from construction machinery has long been a cause of environmental disputes, especially to the nearby residents. In 2008, the Ministry of Environment adopted the construction machinery noise labeling system to encourage the development of the low noise construction machinery. After the implementation of the noise labeling system of the construction machinery, the noise emitted from the construction machinery has been decreased over the six years. But, as the quality of life improves, a growing number of people desire more comfortable and quite living environment. Under the situation, new systems like the low noise labeling system are considered to encourage the development of the low noise construction machinery. In accordance with the low noise labeling system, the construction machinery satisfying the standard of low noise are qualified to attach the low noise label in front of the products. Thus, the product qualified the low noise certification will be incentivized by the choice of the consumer. In this paper, we have studied the necessity of the low noise labeling system for the construction machinery and the considerations to adopt the low noise labeling system of construction machinery. And we have studied appropriate criterion to judge the low noise construction machinery. The considerations studied in this paper will be helpful to adopt the low noise labeling system of construction machinery in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.91-96
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• 2000

In this paper a simulation program is developed to abate the aircraft noise in the buildings near the airport. This indoor aircraft noise prediction computer program, which is based on the various data and measured results, is useful for the understanding the noise reduction efficiency of the existing buildings as well as for the effective noise abatement method to keep the optimum indoor level for quiet environment.

• KIEAE Journal
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• v.17 no.1
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• pp.83-89
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• 2017

Purpose: Thermal sensation or thermal comfort was randomly used in many studies which focused on combined effects of thermal and acoustic environments on human perception. However, thermal sensation and thermal comfort are not synonyms. Thermal comfort is more complex human perception on thermal environment than thermal sensation. This study aims to investigate effects of noise on thermal sensation and thermal comfort separately, and also to investigate effects of temperature on acoustic sensation and comfort. Method: Combined thermal and acoustic configurations were simulated in an indoor environmental chamber. Twenty four participants were exposed to two types of noise (fan and babble) with two noise levels (45 dBA and 60 dBA) for an hour in each thermal condition of PMV-1.53, 0.03, 1.53, 1.83, respectively. Temperature sensation, temperature preference, thermal comfort, noisiness, loudness, annoyance, acoustic comfort, indoor environmental comfort were evaluated in each combined environmental condition. Result: Noise did not affected thermal sensation, but thermal comfort significantly. Temperature had an effect on acoustic comfort significantly, but no effect on noisiness and loudness in overall data analysis. More explicit interactions between thermal condition and noise perception showed only with the noise level of 60 dBA. Impacts of both thermal comfort and acoustic comfort on the indoor environmental comfort were analyzed. In adverse thermal environments, thermal comfort had more impact than acoustic comfort on indoor environmental comfort, and in neutral thermal environments, acoustic comfort had more important than thermal comfort.

• Journal of the Korean Home Economics Association
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• v.43 no.4 s.206
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• pp.31-47
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• 2005

This study is a preliminary investigation into improving the environmental quality of schools. The purpose was to clarify the present conditions and reasons of noise in elementary schools located near airports and roads by noise level measurements and questionnaire surveys of subjective responses. fold measurements on equivalent and instantaneous noise levels, indoor and outdoor, were carried out in 3 schools during the periods 11th~ 13th of February and 2nd~ 7th of July,2003. The respondents were 94 teachers working in the 3 schools. The results were as follows. 1) Indoor noise levels of the 3 schools were 36.g~73 dB(A) in winter, and 46.9~ 91 dB(A) in summer. These values were higher than the indoor noise standard of 50 dB(A), except for the average of equivalent noise levels in winter.2) Outdoor noise levels of the schools were 41.1 ~ 101 dB(A) in winter, and 52.4~ 102 dB(A) in summer. These values were generally inappropriate relative to the standard for environmental noise of 65 dB(A). 3) The respondents showed relatively non- positive responses during school hours for interruptions by environmental noise.4) The frequently checked types of environmental noise of the schools were 'airplane noise','surrounding facilities', and 'traffic noise'. The frequently checked types of damage by environmental noise were 'Interrupting school hours' and 'Interrupting business'.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.830-833
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• 2004

An indoor package air-conditioner (PAC) has complex noise sources such as motor noise and fluid noise caused by the fan motor, heat transfer and shroud. Sound intensity techniques and ODS(Operational deflection shape) techniques are applied to identify the noise characteristics of an indoor air-conditioner's cabinet. The sound intensity is used to visualize the noise source locations. and the ODS to visualize the vibration pattern and to obtain the dynamic characteristics of the noise source. Acoustic intensity and operational deflection distribution are obtained in space domains as well as frequency domains. Using the visual information of source locations and its dynamic characteristics, the damping patch is applied to reduce structure borne noise in the cabinet. As a result, the noise emitted by the cabinet is reduced by 5dB.

• Journal of Environmental Health Sciences
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• v.45 no.6
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• pp.668-674
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• 2019

Objectives: Modern people spend most of their day indoors. As the health impact of radon becomes an issue, public interest also has been growing. The primary route of potential human exposure to radon is inhalation. Long-term exposure to high levels of radon increases the risk of developing lung cancer. Radon exposure is known to be the second-leading cause of lung cancer, following tobacco smoke. This study measures the indoor radon concentrations in detached houses in area A of Chungcheongbuk-do Province considering the construction year, cracks in the houses, the location of installed detectors, and seasonal effects. Methods: The survey was conducted from September 2017 to April 2018 on 1,872 private households located in selected areas in northern Chungcheongbuk-do Province to figure out the year of building construction and the location of detector installed and identify the factors which affect radon concentrations in the air within the building. Radon was measured using a manual alpha track detector (Raduet, Hungary) with a sampling period of longer than 90 days. Results: Indoor radon concentrations in winter within area A was surveyed to be 168.3±193.3 Bq/㎥. There was more than a 2.3 times difference between buildings built before 1979 and those built after 2010. The concentration reached 195.4±221.9 Bq/㎥ for buildings with fractures and 167.2±192.4 Bq/㎥ for buildings without fractures. It was found that detectors installed in household areas with windows exhibited a lower concentration than those installed in concealed spaces. Conclusion: High concentrations of indoor radon were shown when there was a crack in the house. Also, ventilation seems to significantly affect radon concentrations because when the location of the detector in the installed site was near windows compared to an enclosed area, radon concentration variation increased. Therefore, it is considered that radon concentration is lower in summer because natural ventilation occurs more often than in winter.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.85-90
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• 2014

The purpose of this study is to analysis the 3 differential size of the interior space for impulse noise. To achieve this goal the 3 kinds (27, 35, $50m^3$) of interior space were performed comparing the impulse noise. Result of this study, the standard error of the mean peak sound pressure of value from 0.19 to 0.27dB and there was no significant difference (p<0.01). And B-duration is significant differences (P<0.01) range from 3.98 to 7.93ms. This is respectively less than 10ms. These findings are confirmed in accordance by the 3 differential space size of the indoor-impulse noise due to 0.3 dB or less, so there was no difference to the operational influence. And also below 100 Hz were found fundamental mode frequency analysis. Results were matched with calculated theoretical values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11C
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• pp.1498-1509
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• 2004

In this paper, we evaluate the performance of a noncoherent OOK (On-Off Keying) UWB (Ultra Wide Band) system based on power detection with noise power calibration and noise power windowing for ubiquitous sensor network applications in typical indoor wireless channels. Utilizing noise power calibration and noise power windowing, the current noise information can be initially or adaptively provided to determine suitable detection threshold value for signal demodulation. Simulation results show that the noncoherent OOK UWB system using noise power calibration achieves good BER (Bit Error Rate) performance which is favorably comparable to that of the system using the ideal adaptive threshold, while maintaining simple receiver structure. However, despite the serious loss of the data transmission rate, the performance improvement by noise power windowing is not so remarkable. furthermore, these performance results are similarly maintained in BEE 802.15 Task Group 3a UWB indoor channel model, and it is also revealed that the BER performance can be significantly improved by increasing the pulse repetition rate.