• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.615-621
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• 2011

There are hundreds of thousands call center workers wearing acoustic device. However, researches and noise exposure measurements on the noise transmitted from acoustic devices have seldom been performed due to the difficulty of measurement and to the absence of the measuring method in Korea. The aim of this study is to set up management measures to protect hearing loss on the call operator by acquiring measurement data of noise transmitted from the headset. Noise exposure measurements of 17 operators were performed in 7 call centers and head and Torso simulator method in compliance with the ISO standard 11904-2 was used for the measurement of noise transmitted from the headset. Sound pressure levels(SPL) transmitted from the headset were 73.2~86 dB(A). The operator exposed to the highest SPL set up his volume control at 9 which was the highest volume level. The volume control level, adjustable from 1 to 9, could be identified 12 out of 17 operators and the range of volume levels was 4.5~9. As a result of pearson correlation analysis, the correlation between volume level and SPL transmitted from the headset showed high relation as significance at the 0.672 level(p<0.05). To protect hearing loss of call center operators, it is more practical and effective measure to limit the volume level below the noise exposure level, i.e. 85 dB(A), rather than to carry out noise monitoring considering cost-effective aspect.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.993-995
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• 2014

Typical dwelling pattern of apartment houses in Korea. Because of this the noise of life problem arise, complaints are surging. In real-life, if suffering is unavoidable due to ambient noise, to handle a civil complaint the using a noise meter. At home, it is difficult to measure the noise using professional equipment. So, many uses smartphone application in general. But released existing noise measurement application has different value from the sensor sensitivity for each smartphone model to same situation. The value is lacks precision and this is not considered as having been made by measuring the actual noise purpose. Therefore in this paper, we propose a mobile data processing system for the living environment of noise measurement using a smartphone. Benefits of this study is to improve the accuracy of noise measurements and to find direction of noise to handle complaints.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.607-611
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• 2006

There are several methods to obtain structural vibration for analysis of vibro-acoustic noise. First of all, vibration data can be obtained through the structural analysis using finite element method. Although this method has no need to experiment, the analysis result is unreliable when the structure and the vibration source is complex to model exactly. The second method is to measure vibration using a number of sensors. The analyzed vibro-acoustic noise with directly measured data is setting morereliable when the number of data acquisition points is getting larger. However, it requires large amount of time and effort to measure all vibration data on every node especially when the size of vibrating structure is large. The Modal Expansion Method(MEM), which uses mode information and measurement data, has been introduced to compensate their limits. With a relatively small number of measurement data, the reliable structural vibration for vibro-acoustic noise can be obtained using this semi-analysis method. Although MEM gives reliable result, it is restricted by the number of modes and measurement points. In this paper, structural analysis, direct vibration measurement method and MEM are compared using the simple aluminum box model. Furthermore, the washing machine case is also provided as a comparative example. The Laser Doppler Vibrometer(LDV) was used instead of contact type accelerometer to get vibration data.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.1
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• pp.28-36
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• 2018

The experimental results of the model tests for the twin propeller cavitation noise are presented. The model test was carried out by means of procedure of noise measurement followed by the signal processing and full-scale extrapolation. In order to convert the measured sound pressure level into the sound source level, transfer function measurements for three conditions were performed according to the combination of locations and number of virtual sources. White noise and LFM signal were used as a source signals to examine the influence of the input signal. For the twin propellers, 5 transfer functions were defined and the results were discussed. Cavitation noise measurement tests were performed similarly to the transfer function measurement test. Noise source localization analysis was performed to confirm the test effectiveness. It was confirmed that the source level of the twin propeller can be estimated reliably by using transfer function corrections. Finally, the model test results were converted into full-scale by applying the ITTC '87 model-ship scaling raw, and the validity of the model test was confirmed by comparison with the full-scale measurement result.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.57-57
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• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.316-318
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• 2012

• International Journal of Automotive Technology
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• v.4 no.1
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• pp.21-30
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• 2003

In this paper a systematic test procedure for evaluation of road-induced noise of a vehicle and guidelines for each test are presented. Also, a practical application of the test procedure to a small SUV is presented. According to the test procedure, all the tests were performed to evaluate road-induced booming noise that is in low frequency range. First of all the information on characteristics of road-induced noise was obtained through baseline test. Coupling effects between body structure and acoustic cavity of a compartment were obtained by means of modal tests for a structure and an acoustic cavity. Local stiffness of joint areas between chassis system and car-body was determined by test for measurement of input point inertance. Noise sensitivities of body joints to operational forces were obtained through test for measurement of noise transfer functions. Operational deflection shapes made us analyze behaviors of chassis system under running condition and then find sources of noise due to resonance of the chassis system. Finally, Principal Component Analysis and Transfer Path Analysis were utilized to investigate main paths of road-induced noise. In order to evaluate road-induced booming noise exactly, all of tests mentioned above should be performed systematically.

• International Journal of Railway
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• v.4 no.2
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• pp.42-49
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• 2011

Today, rolling stock has become a fast and convenient mode of transportation and has witnessed increased demand. But the speed improvement has resulted in increased aerodynamic noise and therefore residential districts near the railroad tracks are exposed to ever increasing noise level. A study on methodologies for measuring and appraising rolling stock's environmental noise has therefore become an important area of endeavor. In the case of the environmental noise, there are no changes in tone so prediction can be made by reducing areas around the railway. The present study explores estimation of the noise around the railway using scale model, and the source of the noise has been investigated as well. The scale model of rolling stock will have to be able to measure high frequency noise and it is required to be generated in a short amount of time. Since popping a balloon or firing a gun fits this requirement the present study analyzed the characteristics of these two different noise sources. Measurement was made in a large vacant lot and the reflection due to the ground was also examined. The method proposed here can be used in the future for predicting the environmental noise of railway vehicles.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.41
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• pp.221-229
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• 1997

This study concerns with the comparing and evaluation for Signal - Noise Ratio of the quantitative signal factors in the measurement devices for developing efficiency for product system. On the basis of this conditions and purpose, this study presents a general procedure for deriving the Signal - Noise Ratio, confidence intervals and significiant testing for the measurement devices.

• Proceedings of the Acoustical Society of Korea Conference
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• 1997.06a
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• pp.68-74
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• 1997

Ship radiated noise is an infortant parameter which dtermines Anti Submarine Warfare(ASW) countermeansure or passive Sonar detection and classification performance. Its measurement should be performed under controlled ocean acoustic environment. In data reduction of the measured data from hydrophone array, theeffect fo ambient noise, surface reflection and bottom reflection etc. should be compensated to obtain the source level of the ship radiated noise. This study describes the measurement hydrophone array design criteria based on the analysis of transimission anomaly due to the surface reflection.