• The Journal of Engineering Geology
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• v.16 no.2 s.48
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• pp.161-169
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• 2006

A short seismic reflection survey was performed to map the basement and the upper units in the Gomso Bay. This research was mainly aimed at clarifying the basement by improving the signal-to-noise ratio in data processing steps. The strategies employed in this research included enhancement of the signal interfered with large-amplitude noise, through pre- and post-stack processing such as time-variant filtering, bad trace edit, careful muting after f-k filter and NMO correction. The subsurface structure mapped from this survey mainly consists of the top of basement and the upper three units, which were well correlated to the result from the previously conducted MT survey. Furthermore seismic section clarifies approximately 30m deep subhorizontal event of the top of the basement, which was not shown in the central portion of the MT section due to data qualify.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.264-274
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• 2012

Evaluation on the environmental noise is carried out by surveying subjective response of residents with physical measurement of noise during long period in field. Particularly field survey is used to make regulations from the analysis on how many people are annoyed for specific noise level, and laboratory test used to analyze the relationship between physical parameters of noise and subjective responses. In the laboratory controlling the variables is easy but the results could be biased because the condition in room would be different with field. Most of all noise exposure time is considered to be different with real situation, and this study aimed to evaluate the subjective response by exposure time of transportation noise, by applying three kinds of variable how much they give effects on the annoyance as the exposure time is operating condition, windows type and sound level. As a result there was somewhat difference between operating type and annoyance, which is caused by the sound characteristics operated in different condition. However the window type didn't give much effect to the annoyance as much as sound type. This means that the subjective response could give similar result by exposure time even for different window types. Most of all, the main factor affecting subjective response is considered to be the sound level and the exposure time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.272-280
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• 2009

Measurement of the background radio noise is very important process being used in survey of radio noise environment, calculating the threshold level for the frequency occupancy measurement and so forth. First step of background radio noise measurement is to select the sample sub-band which is mostly dominated by the background white Gaussian noise (WGN) within the target band. The second step is to carry out the main measurement of radio noise on this selected sample sub-band for the representative value of the noise power. In this paper, a method for selection of sample sub-band for the effective background radio noise measurement using SVD is proposed under the assumption that background radio noise is WGN. The performance of the proposed method is compared with that of the APD method which is widely used for the same purpose. Simulation results are shown to demonstrate the high performance of the proposed method in comparison with the existing APD method.

• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.274-281
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• 2015

Although noise-induced hearing loss (NIHL) is a significant public health problem, many people might not be aware that exposure to loud noise could occur hearing loss. The purpose of this study is to evaluate and analyze how importantly and seriously people are aware of NIHL using a 22-question survey. It was administered to random 150 people including between 20 s to 60 s. The questionnaire contained questions about i) views toward general health issues including hearing loss and tinnitus, ii) noise exposure, and iii) views toward hearing protection. Results showed that hearing loss was defined on a likert scale as 'a very big problem' by 17.33 % of respondents compared with other health issues. Surprisingly, most respondents (82 %) had not heard, read, or seen anything lately related to the issue of hearing loss. Many respondents had experience hearing problem or tinnitus under loud noise situations (85 %), however, only 11.33 % of respondents had used earplugs. Fortunately, many could be motivated to try ear protection if they were advised by a medical professional (80 %) or were aware of the potential for permeant hearing loss (78.67 %). We concluded that awareness of the potential for permanent hearing loss with noise and effective methods of hearing protection should be announced to public for preventing NIHL.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.939-942
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• 2007

Vacuum cleaner is a close life product that can remove various dusts from our surroundings. However well vacuum cleaner clean our environments, many people are looking away from it, due to its loud noise. Its noise causes a big trouble in the usual life, for example, catch calls, TV watching and discussing etc. To reduce these inconveniences, noise reduction methods and systematic design of low noise vacuum cleaner are studied in this paper. At first, sound quality investigation is performed to get the noise level and quality that make people TV watching and catch calls available. Based on the European and domestic customer SQ survey result, sound power, peak noise level and target sound spectrum guideline are studied and introduced. As a second, precise product sound spectrums are designed into each part based on the sound quality result. Fan-motor, brush, mainbody, cyclone spectrums are decided to get the final target sound based on the contribution level. Fan-motor is the major noise source of vacuum cleaner. Specially, its peak sound, RPM peak and BPF Peak, cause the people nervous. To reduce these peak sounds, high rotating impeller and diffuser are focused due to its interaction. A lot of experimental and numerical tests, operation points are investigated and optimization of flow path area between diffusers is performed. As a bagless device, cyclones are one of the major noise sources of vacuum cleaner. To reduce its noise, previous research is used and adopted well. Brush is the most difficult part to reduce noise. Its noise sources are all comes from aero-acoustic phenomena. Numerical analysis helps the understanding of flow structure and pattern, and a lot of experimental test are performed to reduce the noise. Gaps between the carpet and brush are optimized and flow paths are re-designed to lower the noise. Reduction is performed with keeping the cleaning efficiency and handling power together and much reduction of noise is acquired. With all above parts, main-body design is studied. To do a systematic design, configuration design developments technique is introduced from airplane design and evolved with each component design. As a first configuration, fan-motor installation position is investigated and 10 configuration ideas are developed and tested. As a second step, reduced size and compressed configuration candidates are tested and evaluated by a lot of major factor. Noise, power, mass production availability, size, flow path are evaluated together. If noise reduction configuration results in other performance degrade, the noise reduction configuration is ineffective. As a third configuration, cyclones are introduced and the size is reduced one more time and fourth, fifth, sixth, seventh configuration are evolved with size and design image with noise and other performance indexes. Finally we can get a overall much noise level reduction configuration. All above investigations are adopted into vacuum cleaner design and final customer satisfaction tests in Europe are performed. 1st grade sound quality and lowest noise level of bagless vacuum cleaner are achieved.

• Explosives and Blasting
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• v.11 no.1
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• pp.5-33
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• 1993

On the cable Tunnel works. Cautious blasting works were so effective and carried out. The vibration record were under 0.4cm / sec and blasting noise are under 75dB Which it was measured at the ground of Tailor House. As a result cautious blasting works under above allowable value, are not Influenced the structure of house and living. On the architechtural survey, there were some hair crack on the wall but this was not crack from recently blasting work.

• Journal of Preventive Medicine and Public Health
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• v.7 no.1
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• pp.177-183
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• 1974

It is generally recognized that the environmental noise of the various working places thought to be the cause of hearing disturbance. This survey was carried out to evaluate the prevalence of noise-induced occupational bearing loss among the weavers of 39 textile industries in Taegu, Korea. For this survey, 432 male workers and 2,023 female workers were examined their hearing acuity by Individual pure tone threshold determination test(air conduction), from November, 1972, to January, 1973. Main findings were as follows : 1. The mean of noise intensity of the 54 weaving rooms was, in over all, $95.6{\pm}4.2dB\;(A),\;95.9{\pm}4.0dB\;(B)\;and\;96.2{\pm}3.9dB\;(C)$. 2. The mean hearing threshold levels by service years in the 4,000 Hz were intensively increased from 1st to 3rd year and slightly decreased. than that of 3rd year, from after 3rd to 5th year, after 5th year that increased slightly. 3. The mean hearing threshold levels by frequencies were highest in the 4,000 Hz(male: $25.0{\pm}11.3dB$, female: $22.0{\pm}10.2dB$) and followed by 6,000, 8,000 and 3,000 Hz. 4. The mean hearing threshold level of the 6,000 Hz (male: 17.0 dB. female: 17.9dB) was higher than that of 4,000Hz (male: 16.4 dB, female: 17.1dB) in tile 1st service year. 5. The mean hearing loss of examinees was $16.2{\pm}8.0dB$ in male and $15.4{\pm}7.8dB$ in female.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.94-101
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• 1998

This paper presents the psychoacoustic analyses on the vehicle interior, noise generated when accelerating. Following the objective quantification for vehicle noises of different classes, the subjective decision process by the jury test is adopted to interrelate these results based on two different approaches. In particular, the paired comparison method is employed in assessing the sound quality in terms of the quietness, the powerfulness, and the pleasantness of the human auditory sensation. Special attention is paid to the physical interpretation of psychoacoutic parameters and their interrelation to the subjective assessment scores. In order to ensure the integrity of statistics of the survey, various tests are performed. The results show that the consistency of the "quiet" sensation is far higher than that of the "powerful" and the "pleasant" sensations. Also, it is found that the most significant parameter determining these feelings turns out to be the inherent loudness of the noise instead of the conventional indicators such as the weighted sound pressure level. It may be concluded that the psychoacoustic analysis offers more realistic evaluation for vehicle noise and assists the improvement of NVH more efficiently.ement of NVH more efficiently.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.332-339
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• 2007

As the economy has grown and the main industry in Korea has been changed from secondary industry to tertiary industry, the importance of indoor environment has been a matter of common concern, in which one of the main concerns is to improve the indoor acoustic conditions. However, even though this is required more than before, there are no measures to protect the human being from the noise of electric home appliances. This is owing to the absence of the data about sound power level of electric home appliances. So, we investigate the sound power level of them and analyze the acoustical characteristics of each one. First, we tried to investigate the sound power measurement method of each electric home appliance. After it we test the sound power level of them. From the survey, we can know that the vacuum cleaner is the most noisy electric home appliance, and the refrigerator is the least noisy one. The noise of a range hood is distributed over a wide range frequency. Lastly, we intented to propose the proper method measuring sound power level on each electric home appliance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.4
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• pp.335-346
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• 2009

As the economy has grown and the main industry in Korea has been changed from secondary industry to tertiary industry, the importance of indoor environment has been a matter of common concern, in which one of the main concerns is to improve the indoor acoustic conditions. However, even though this is required more than before, there are no measures to protect the human being from the noise of electric home appliances. This is owing to the absence of the data about sound power level of electric home appliances. So, we investigate the sound power level of them and analyze the acoustical characteristics of each one. First, we tried to investigate the sound power measurement method of each electric home appliance. After it we test the sound power level of them. From the survey, we can know that the vacuum cleaner is the most noisy electric home appliance, and the refrigerator is the least noisy one. This results will help us predict the indoor noise level using the basic data of sound power level.