• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.80-85
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• 2016

In this paper, by comparatively analyzing horn type speaker and line array type speaker developed based on line sound source theory and point sound source theory, we research whether theory is adaptable or not in real. Academically, point sound source is attenuated as much as 6dB in accordance with double distance and line sound source is attenuated as much as 3dB in accordance with double distance. Line array speaker system developed based on line sound source is analyzed by theory of line sound source about occurring small sound pressure attenuation and it is propose of research that array composition of right speaker is selected in accordance with use purpose and environment. For this purpose, we analyze theory of point sound source and line sound source. we analyze parameter value by simulating designed horn type speaker and line array speaker based on theory.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.751-755
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• 2005

We propose a sound source localization method using the Head-Related-Transfer-Function (HRTF) to be implemented in a robot platform. In conventional localization methods, the location of a sound source is estimated from the time delays of wave fronts arriving in each microphone standing in an array formation in free-field. In case of a human head this corresponds to Interaural-Time-Delay (ITD) which is simply the time delay of incoming sound waves between the two ears. Although ITD is an excellent sound cue in stimulating a lateral perception on the horizontal plane, confusion is often raised when tracking the sound location from ITD alone because each sound source and its mirror image about the interaural axis share the same ITD. On the other hand, HRTFs associated with a dummy head microphone system or a robot platform with several microphones contain not only the information regarding proper time delays but also phase and magnitude distortions due to diffraction and scattering by the shading object such as the head and body of the platform. As a result, a set of HRTFs for any given platform provides a substantial amount of information as to the whereabouts of the source once proper analysis can be performed. In this study, we introduce new phase and magnitude criteria to be satisfied by a set of output signals from the microphones in order to find the sound source location in accordance with the HRTF database empirically obtained in an anechoic chamber with the given platform. The suggested method is verified through an experiment in a household environment and compared against the conventional method in performance.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.183-191
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• 2021

A time-series variation of temperature, salinity, and underwater sound speed was analyzed using an Array for Real-time Geostrophic Oceanography (ARGO) float which autonomously collects temperature and salinity for about 10month with 2 days cycle among 12 floats in the center of the Yellow Sea. As a result, the underwater sound channel appeared below the thermocline as the surface sound channel, which is dominant in the winter season, reduced in April. Besides, for a certain time in the spring season, the sound ray reflected the sea surface frequently due to the short-term temperature inversion effect. Based on the case of successful observation of ARGO float in the shallow water, using prolonged monitoring unmanned platform may contribute to predicting sound transmission loss if the temperature inversion and sound channel including background environment focusing are investigated in the center of the Yellow Sea.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.49-54
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• 2016

The wind power plants were installed in many places because of the low climate changing effects since 2000. Generally, the wind power plants located in the seaside and the mountainous area and the heights of the windmills are about 40 m~140 m above the ground level. So the noises emitted from the wind power plants propagate far away compared with other environment noise sources like trains and cars noise. Because of these reasons, the noise emitted from the wind power plant is easy to cause the additional social problems like as noise complaints. Under the situation, the ministry of environment has established the guideline to evaluate the environmental effects for the wind power plant. According to the guideline, the noise of the wind power plant has to meet 55 dB(A) at daytime and 45 dB(A) at night in the residential area, which is regulated in the noise and vibration management law. But, it is difficult to estimate the noise emitted from the wind power plant because of the absence of the prediction model of the wind power plant noise. Therefore, the noise prediction model for wind power plants using the regression analysis method is developed in this study. For the development of the model, the sound pressure levels of the wind power plants in Jeju island are measured and the correlations between the sound pressure levels are analyzed. Finally, the prediction equation of the wind power plant noise using by regression analysis method derived. The prediction equation for the wind power plant noise proposed in this study can be useful to evaluate the environmental effects in any wind power plant development district.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.59-64
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• 2018

PURPOSES : We propose a parameter-setting-free harmony-search (PSF-HS) algorithm to determine the individual sound power levels of noise sources in the cases of industrial or road noise environment. METHODS :In terms of using methods, we use PSF-HS algorithm because the optimization parameters cannot be fixed through finding the global minimum. RESULTS:We found that the main advantage of the PSF-HS heuristic algorithm is its ability to find the best global solution of individual sound power levels through a nonlinear complex function, even though the parameters of the original harmony-search (HS) algorithm are not fixed. In an industrial and road environment, high noise exposure is harmful, and can cause nonauditory effects that endanger worker and passenger safety. This study proposes the PSF-HS algorithm for determining the PWL of an individual machine (or vehicle), which is a useful technique for industrial (or road) engineers to identify the dominant noise source in the workplace (or road field testing case). CONCLUSIONS : This study focuses on providing an efficient method to determine sound power levels (PWLs) and the dominant noise source while multiple machines (or vehicles) are operating, for comparison with the results of previous research. This paper can extend the state-of-the-art in a heuristic search algorithm to determine the individual PWLs of machines as well as loud machines (or vehicles), based on the parameter-setting-free harmony-search (PSF-HS) algorithm. This algorithm can be applied into determining the dominant noise sources of several vehicles in the cases of road cross sections and congested housing complex.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.1-8
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• 2010

In this paper, a sound externalization method is proposed for out-of-the-head localization in a headphone listening environment. In order to reduce timbre distortion by the conventional methods using a measured a head-related transfer function (HRTF) or early reflections, the proposed method integrates a model-based HRTF with reverberation. In addition, for improving frontal externalization performance, techniques such as decorrelation and spectral notch filtering are included. To evaluate the performance of the proposed externalization method, subjective listening tests are conducted by using different types of sound sources such as white noise, sound effects, speech, and music. It is shown from the test results that the proposed externalization method can localize sound sources farther away from out of the head than the conventional method.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.91-97
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• 2010

Recently, Internet users have an interest about Social Media Service in Web2.0 environment. We suggest the orchestra service as social media service to meet user satisfactions in changed web environment. We accept a concept of the MMMD (Multiple Media Multiple Devices). In other words, Internet users listen to the music not only one device but multiple devices. Each one of multiple devices can play a sound source under earmark instruments for providing users with actual feeling like an orchestra. To meet the purpose, we define 3 steps. First, we separate the sound source based on instrument information. Second, we exact the suitable sound source for play orchestra. In final step, the sound source transmits to each suitable playing device. We named the 3 step for AET process. Beside we suggest synchronization method using rest point in the MIDI file for control sound sources. Using the AET process and synchronization method we provide the orchestra service for meet user's satisfactions to users.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.948-955
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• 2017

Currently, porous materials (e.g., mineral wool) are the core materials used in offshore plant panels, but in spite of their superb acoustic performance, these items must be replaced for environmental reasons. A honeycomb structure is widely used throughout the industry because of its high strength-to-weight ratio. However, research in terms of noise and vibration is minimal. An acoustic study should be conducted by taking advantage of honeycomb structures to replace porous materials. In this study, a simulation was performed assuming that a honeycomb panel is a superposition of symmetric mode and antisymmetric mode. Reliability was verified by comparing a simulation results based on a theory with a experimental results, and the possibility of the panel as a core material was evaluated by studying the sound insulation characteristics of a honeycomb. As the panel thickness increased, the coincidence frequency shifted to low frequency. As the angle between horizontal line and oblique wall and cell-size decreases, the sound insulation performance is improved. And as the cell-wall thickness increased, the sound insulation performance improved.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.139-144
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• 2015

Recently, to realize sound-absorbing structures, we have to insert sound-absorbing materials into wall. These shapes are taken limitations because sound-absorbing materials should be fixed. Therefore, the sound absorption is changed by environment that used the sound-absorbing materials. On the other hand, we will take same effect without sound-absorbing material, if we change the shape of wall to sound absorbing structure. If we use this sound absorbing structure, we can get benefits by removing limitation of materials. Therefore we suggest perforated plate for effective sound-absorbing structure. We confirmed the function of sound-absorption of this structure using equivalent property. Then, we found the similarity between perforated plate and resonator. Also, we verify these theories through computer simulation by FEM(Finite Element Method). Finally, we validated that perforated plate has function of sound absorption without sound-absorbing material. This perforated plate is used for sound-absorbing material of buildings and transportations such as vehicle, train etc. Also, these results could be further used basic tool for design of sound-absorption structure.

• Journal of Environmental Health Sciences
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• v.45 no.4
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• pp.394-395
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• 2019