• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.135-138
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• 2005

On the basis of theoretical studies on the effect of the cylinders attached to semi-infinite screens, the effect of the tangential sound power-transport along the cylindrical top section of noise barriers is studied. Four types of acoustical mechanism between the surface of the cylinder and the adjacent air particles are investigated, namely Z $\rightarrow$ $\infty$, Z $\rightarrow$ pc, Z $\rightarrow$ 0 and actively controlled surface sound field. In active control case the sound power parallel to the surface of the attached cylinder is minimized by means of a secondary sound field, which is generated from a part of the attached cylinder. In each case the change in the acoustical shadow zone was shown and compared. The numerical study shows the possibility of deflecting the incident sound by minimizing the acoustical surface impedance of the upper sections.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.764-769
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• 1994

The impedance of an electro-acoustic transducer can be controlled by motional feedback, and the noise in a duct can be reduced actively by adjusting the impedance using an additional sound. In this paper, two approaches for active noise control using motional feedback (MFB) loudspeaker are described. First configuration uses an external sensor to pickup of source directly. In this configuration, the adaptation of controller is necessary to compensate the change of transfer function from noise source to control poing. The second configuration uses a new adaptive algorithm specialized for peridic noise. Because this configuration does not require any reference input and the error sensor couples very tightly with control loudspeaker, this MFB system itself is independent of the duct condition. No microphone are required in both configurations, so that a more reliable and stable active control system can be realized under severe conditions such as high pressure, high temperature, dust, flow and so on.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.3
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• pp.1-9
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• 2009

Noise reduction for hydraulic pump is strongly demanded in the market with its efficiency and durability. In order to meet this demand, it is necessary to reveal mechanism for noise and relationship between the important factors. In this paper, mathematical model for cylinder pressure which is primary reason of pulsation and sound noise were established, and examined its pressure profile by simulation. Also, the valve plate of three kind types are manufactured and tested for piston pressure, pressure pulsation, and sound power level based on the tentative standard which is officially recognized.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.229-235
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• 2011

Traffic noise pollution is a growing problem that highly affects the health of people in urban areas. In order to implement effective measures against traffic noise the noise mapping about its distribution is imperative. Urban traffic noise maps will help to establish the existing baseline so that we will be able to look for the effective way to control the noise. They will also let us see in an understandable and visual way how noise spreads from roads into residential areas. In this paper we considered three development types between roads and residential areas, and applied the interpolation of ArcGIS for noise attenuation with distance from the roads to find the noise level at the parcels positions in residential areas, and then generated the noise map using the interpolated results. Therefore we present results that the traffic noise level within residential areas exceed the national noise standard and also can estimate the noise level of individual parcels. These results can be used for traffic noise control planning or assessment of officially assessed land price in near future.

• International conference on construction engineering and project management
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• 2020.12a
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• pp.455-462
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• 2020

Noise which is unwanted sound is a serious pollutant that can affect human health, as well as the working and living environment if exposed to humans. However, current noise management on the construction project is generally conducted after the noise exceeds the regulation standard, which increases the conflicts with inhabitants near the construction site and threats to the safety and productivity of construction workers. To overcome the limitations of the current noise management methods, the activities of construction equipment which is the main source of construction noise need to be managed throughout the construction period in real-time. Therefore, this paper proposed a framework for automatically detecting noise sources in construction sites in real-time based on convolutional neural networks (CNNs) according to the following four steps: (i) Step 1: Definition of the noise sources; (ii) Step 2: Data preparation; (iii) Step 3: Noise source classification using the audio CNN; and (iv) Step 4: Noise source detection using the visual CNN. The short-time Fourier transform (STFT) and temporal image processing are used to contain temporal features of the audio and visual data. In addition, the AlexNet and You Only Look Once v3 (YOLOv3) algorithms have been adopted to classify and detect the noise sources in real-time. As a result, the proposed framework is expected to immediately find construction activities as current noise sources on the video of the construction site. The proposed framework could be helpful for environmental construction managers to efficiently identify and control the noise by automatically detecting the noise sources among many activities carried out by various types of construction equipment. Thereby, not only conflicts between inhabitants and construction companies caused by construction noise can be prevented, but also the noise-related health risks and productivity degradation for construction workers and inhabitants near the construction site can be minimized.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.732-743
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• 2007

Background noise is one of the major complaints of not only hearing impaired persons but also normal listeners. This paper describes the results of two experiments in which speech recognition performance was determined for listeners with normal hearing and sensorineural hearing loss in noise environment. First, we compared speech enhancement algorithms by evaluation speech recognition ability in various speech-to-noise ratios and types of noise. Next, speech enhancement algorithms by reducing background noise were presented and evaluated to improve speech intelligibility for sensorineural hearing impairment listeners. We tested three noise reduction methods using single-microphone, such as spectrum subtraction and companding, Wiener filter method, and maximum likelihood envelop estimation. Their responses in background noise were investigated and compared with those by the speech enhancement algorithm that presented in this paper. The methods improved speech recognition test score for the sensorineural hearing impaired listeners, but not for normal listeners. The results suggest the speech enhancement algorithm with the loudness compression can improve speech intelligibility for listeners with sensorineural hearing loss.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.599-602
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• 2005

This paper describes a experimental study determining the effects of the type and loudness of introducing sounds on the amenity and the masking degree of background noise. 132 relative test sounds with 11 types of introducing sounds and 3 steps of road traffic noise were presented to 29 subjects through headphone in the laboratory experiment. Seven scale of polar adjective such as 'Strong Weak', 'Pleasant Unpleasant', 'Clear Unclear', 'Suitable Unsuitable', 'Comfortable-Discomfortable' was employed for the evaluation of amenity. And Seven scale of mono polar adjective such as 'Very-Not at all' was employed for the evaluation of masking degree against road traffic noise. The results are as follows; Green music was evaluated the highest amenity among test sounds and murmurs of a stream, signal music, song of a bird, crying of insect was showed the amenity rank of order. The softer and weaker introducing sound was evaluated more suitable and comfortable under the road traffic noise. So adequate level of introducing sounds was considered for the desirable urban soundscape. Also the louder sounds compared to background noises had greater masking effects. But similar levels of introducing sounds were recommended considering both good amenity and masking effects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.592-597
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• 2002

The purpose of this study was to analyze the characteristics of a new heavy weight impactor, the Rubber Ball. Until now Bang-machine has been used to measure the heavy impact noise in accordance with JIS A 1418-1. However, various kinds of examination methods have been needed to make an objective observation of insulation capacity for floor impact noises. Two types of experiments were undertaken. First, the experiment about noise was carried out about an apartment building in actual living condition. Then. vibration noises from the impactors were analyzed. The results of this study were as follows : the result of experiment carried out with bonded area of bail was closer to practical experiment than that of non bonded area. In addition, the result about bonded area of ball was more similar to the result which is claimed by H. Tachibana than that about non bonded area. Moreover, it was found that Rubber Ball has more similar vibration characteristics to the real impact noise source than Bang-machine.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.404-406
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• 2021

In modern society, artificial intelligence and automation are being applied in various fields due to the development of the 4th industrial revolution and IoT technology. In particular, systems with a high proportion of image processing, such as automated processes, intelligent CCTV, medical industry, robots, and drones, are susceptible to external factors noise. In this paper, we propose a digital filter based on noise estimation and weights to reconstruct an image in a complex noise environment. The proposed algorithm classifies the types of noise using noise judgment, and determines the noise level of the filtering mask to switch the filtering process to obtain the final output. In order to verify the performance of the proposed algorithm, simulation was conducted, compared with the existing filter algorithm, and the results were analyzed.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.62-69
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• 2020

This study intended to evaluate noise level of dental handpieces and the effects of noise cancelling devices. An ear model was designed to measure the level of the noise delivered to the inner ear during dental handpiece operation. The level of noise was measured in various conditions using the ear model and the portable noise meter. Noise level was measured again after applying of 4 different noise cancelling devices to the model ear. The noise level of dental handpieces was 82.5 - 84.4 dB. When 4 types of noise canceling devices were applied, the noise level reduced to 67.4 - 73.8 dB. All 4 devices had statistically significant effect in reducing the noise of the handpiece. Considering the intensity and exposure time, noise in dental clinics can cause hearing damage to dentists. For protection from the risk of occupational hearing damages, noise canceling devices can be recommended.