• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1410-1415
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• 2000

This paper introduces the experimental analysis of the resonator in the rolling piston type compressor for air conditioner. The resonator located between cylinder and bearing is a major factor in the noise reduction of the rotary compressor. Several shapes for the resonator which can be built in the space limitations are derived. Then optimal resonator type for the noise reduction is determined by noise tests. 6 design parameters of the type are found and optimal level for each design factor is deduced from Taguchi method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.277-282
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• 2006

Road traffic noise is not produced by any one factor rather occurs as a composition of various factors. Its occurrence is made by running engine noise, tire frictional, and exhaust noise etc. The quality of the noise depends on the size of the vehicles, rotation and engine speed, vehicle load, package state of the road and incline etc. The occurrence of noise level of heavy trucks appears louder than smaller vehicles and the noise levels produced differs according to speed and load etc between similar size vehicles. Other factors such as traffic density, average speed, mixing rate of heavy vehicles, and the distance between vehicles also generate road traffic noise. In this paper we examine 2, 4, and 6-lane roads in Jeonju. Consequently, this study examined the means used to measure road traffic noise. It was found that when there is a large traffic density and the average velocity is below 70 km/hr, the noise level could receive a relative proper value by the current measuring means. But in the case of night-time, it was found that the current measuring method is inapposite.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.3
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• pp.19-33
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• 1998

The primary objective of this research was to develop optimal models for masking the road traffic noise with the sound of a waterfall at urban small green spaces. Noise levels were measured at 8 roadside green spaces in SEOUL and questionnaires were randomly distributed to 40 users for evaluating the noise at each site at the same time. College students participated in the experiment for the development of masking models and the developed models were tested by users at 2 green spaces. The major results are as follows ; 1. Traffic noises ranged from 65dBto 70 dB. Users' satisfaction with the noise became considerably low on the basis of 60 dB and it was highly related to noise level. 2. Noise was a main factor to depreciate the amenity of green spaces where its level was more than 60 dB and so it neds to be excluded or reduced the traffic noise at the process of design. 3. Masking effects kept constant independent of the spatial location of masker on condition that masker levels were equal. It was effective when masker was 5-10dB greater than noise level which was masked. 4. As noise level went up, satisfaction ratings about the masked noise became low but masking effects increased in proportion to its level. 5. It was proved that the models were valid through the field experiment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.41-55
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• 1999

In order to evaluate the effects of knowledge, attitude and practice on noise-induced hearing loss or hearing threshold level, questionnaire survey was performed and hearing thresholds of 1 kHz and 4 kHz were measured on 1,040 subjects with workers exposed to noise, safety and health officers. industrial hygienists, analysts rind office workers. The results were as follows ; 1. The following 6 factors were obtained by factor analysis and factor rotation of 30 questionnaire of knowledge, attitude and practice about noise; knowledge of noise (F1), concern of hearing protective devices (F2), concern of noise induced hearing loss (F3), concern of noise level and hearing impairment (F4), concern of noise in workplace (F5) and recognition of noised-induced hearing loss (F6). 56.1% of variance was explained by 6 factors. 2. Significant variables influencing knowledge, attitude and practice about noise were education level and age in F1, personal protective devices (PPE) and education level in F2, age and education level in F3, education level, age and sex in F4, PPE, education level, age and work duration in F5, and work duration and PPE in F6. 3. Hearing thresholds of 4 kHz were significantly higher in workers exposed to noise than that of in the other subjects and tended to be higher in industrial hygienists, safety and health officers and analysts than that of the office workers. 4. Significant variables influencing hearing thresholds of 1 kHz were age, education level, F5 and F6 in workers exposed to noise, and F1 in industrial hygienists. 5. Significant variables influencing hearing thresholds of 4 kHz were age, F6, sex, work duration, F1, F5, F2 and F3 in workers exposed to noise, F1 and age in safety and health officers, and F6, sex and F4 in industrial hygienists. With the above results, it suggested that workers exposed to noise be needed the education of knowledge, attitude and practice about noise in hearing conservation program for the prevention of noise induced hearing loss. Also, it suggested that health managers in workplace be needed countermeasures to prevent hearing loss although they are intermittently exposed to noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.3 s.120
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• pp.274-281
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• 2007

Road traffic noise is not produced by any one factor rather it occurs as a composition of various factors. Its occurrence is made by running engine noise, tire frictional, and exhaust noise etc. The quality of the noise depends on the size of the vehicles, rotation and engine speed, vehicle load, package state of the road and incline etc. The occurrence of any noise level of heavy trucks appears louder than smaller vehicles and the noise levels produced differs according to speed and load etc between similar size vehicles. Other factors such as traffic density, average speed, mixing rate of heavy vehicles, and the distance between vehicles also generate road traffic noise. In this paper we examine 2, 4, and 6-lane roads in Jeonju. Consequently, this study examines the means used to measure road traffic noise. It was found that when there is a large traffic density and the average velocity is below 70 km/h, the noise level could receive a relative proper value by the current measuring means. But in the case of night-time, it was found that the current measuring method is inapposite.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.713-717
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• 2014

This paper presents a beamforming technique for locating impulsive sound source. The conventional frequency-domain beamformer is advantageous for localizing noise sources for a certain frequency band of concern, but the existence of many frequency components in the wide-band spectrum of impulsive noise makes the beamforming image less clear. In contrast to a frequency-domain beamformer, it has been reported that a time-domain beamformer can be better suited for transient signals. Although both frequency- and time-domain beamformers produce the same result for the beamforming power, which is defined as the RMS value of its output, we can use alternative directional estimators such as the peak value and crest factor to enhance the performance of a time-domain beamformer. In this study, the performance of three different directional estimators, the peak, crest factor and RMS output values, are investigated and compared with the incoherent interfering noise embedded in multiple microphone signals. The proposed formula is verified via experiments in an anechoic chamber using a uniformly spaced linear array. The results show that the peak estimation of beamformer output determines the location with better spatial resolution and a lower side lobe level than crest factor and RMS estimation in noise free condition, but it is possible to accurately estimate the direction of the impulsive sound source using crest factor estimation in noisy environment with stationary interfering noise.

• Journal of Environmental Science International
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• v.6 no.1
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• pp.9-16
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• 1997

We investigated and analysed the actual conditions and characteristics of railroad noise levels for 17 sites in the vicinity of the Seoul-Pusan Line. The results i,we summarized as follows : 11 Railroad noise level ranged to 64 ~ 74 $L_{eq}$ dB(A) at day time and ranged to 60 ~ 72 $L_{eq}$ dB(A) at night time. 21 Increased night noise level depend on the increase of trains passing at night time. 31 The major factor of Increased noise level in the vicinity of stations are using loudspeakers and stream whistle on trains. 4) Decreased effect of noise according to distance is able to be described quantitatively using regression equations of multiplicative model. $L_{eq}$=$78.59^{X-0.056}$, n =25, r=-0.994, s.e. =1.007 $P_{av}$ = $105.68X^{-0.073}$, n =25, r =-0.997, s.e. = 1.007 Also increased and decreased effect of noise according to floor in apartment Is able to be described quantitatively using regression equations of multiplicative model. $L_{eq}$ = $64.238X^{0.0567}$, n = 39, r = 0.787, s.e. = 1.004 $P_{av}$ =79.963X0.0524, n =39, r =0.689, s.e. = 1.056 5) Average noise level in high floor is over 70 $L_{eq}$ dB(A) at day and night time. so more detailed soundproofing countermeasured in high floors apartment is required.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.579-583
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• 2001

Cause of noise/vibration for the sheet feeding apparatus of digital MFP is investigated by analyzing the measured sound pressure and the strategy for reducing the noise level is suggested. Factors related to the noise/vibration are found by loading test and the measurement of the noise by assembling the components. By checking the center distance between gears and the boss height, precision of assembly is identified as a main factor of noise. From the result of analysis, it can be concluded that the noise level of sheet feeding apparatus can be reduced by maintaining the distance between gears and the precision of assembly adequately.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1865-1870
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• 2000

Sound propagation along the surface of the ground can be affected by the roughness of the ground surface and the direction of the wind. Noise Source parameter and ground factor are estimated using the measured results of two points under particular environmental condition, and the noise level of arbitrary points under the same environmental condition can be estimated. The results can be used for the prediction of the noise level from a source above a plain and homogeneous ground surface with no obstacles nearby. Upward and downward conditions are also addressed in addition to ground effect. The proposed method can be utilized to estimate the noise level of specific noise environment and its validity was confirmed with the results of actual field measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1020-1023
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• 2004

Recently, Cooling tower are used the necessary element in a residential area and living space on the viewpoint of indoor temperature control. The purpose of this study is to assistance the comfortable environment and economical measures of noise transmission mechanism on tile cooling tower. The results show that noise evaluation interact the main factor of distance reduction and diffraction reduction. Noise criterion apply to the NC level and equivalent transmission loss about already the design of noise reduction.