• Journal of Digital Convergence
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• v.13 no.7
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• pp.177-182
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• 2015

In a MPC(Multi-Pulse Coding) using excitation source of voiced and unvoiced, it would be a distortion of voice waveform. This is caused by normalization of synthesis speech waveform of voiced in the process of restoration. To solve this problem, this paper present APC-MPC of amplitude-position compensation in a multi-pulses each pitch interval in order to reduce distortion of synthesis waveform. Also, I was implemented that the APC-MPC in coding system. And I evaluate the SNRseg of APC-MPC in 8kbps coding condition of convergence system. As a result, SNRseg of APC-MPC was 13.9dB for female voice and 14.3dB for male voice respectively. And so, I expect to be able to this method for cellular phone and smart phone using excitation source of low bit rate.

• The Journal of the Acoustical Society of Korea
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• v.31 no.3
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• pp.197-204
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• 2012

In this thesis, studied the method to minimize the changes in frequency response and level due to the variation of the distance from the source to the microphone. selecting three microphones (omni directional, cardioid, super cardioid) which are being used generally, frequency responses were measured in accordance with the distance changes. Gotten the difference from the reference as the result of measurement, changed responses for each frequency range were compensated in comparison of the original human vocal source. In low frequency range, the low frequency boost caused by the proximity effect and decrease in accordance with the distance were compensated. The variation in mid-frequency range is comparatively small, however since the mid-range is the most important part of the human vocal signal, were compensated the mid-frequency range in comparison of the reference. The human vocal signal variation in high frequency range is extremely small and the high frequency is compensated close to the original source without difficulty. Understanding the microphone characteristics and compensations, this study showed that the response can be maintain among the change of the distance from the source to the microphone.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.43-49
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• 2012

Noise measurements were performed by distance for major construction equipment. especially, For construction equipment that large width of variations is depending on the type of work, noise measurements were performed by the detail type of work. For a time of quiescent and construction, "A" compensation equivalent noise level (Leq) were measured. Most of the construction equipment and the characteristics of the point source appears to be similar in analyzed noise measurement results.

• Geophysics and Geophysical Exploration
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• v.25 no.3
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• pp.109-119
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• 2022

The computational efficiency of reverse time migration (RTM) based on numerical modeling is not secured due to the high-frequency band of several hundred Hz or higher for data acquired through a three-dimensional (3D) ultra-high-resolution (UHR) seismic survey. Therefore, this study develops an RTM program to derive high-quality 3D geological structures using UHR seismic data. In the traditional 3D RTM program, an excitation amplitude technique that stores only the maximum amplitude of the source wavefield and a domain-limiting technique that minimizes the modeling area where the source and receivers are located were used to significantly reduce memory usage and calculation time. The program developed through this study successfully derived a 3D migration image with a horizontal grid size of 1 m for the 3D UHR seismic survey data obtained from the Korea Institute of Geoscience and Mineral Resources in 2019, and geological analysis was conducted.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.70-75
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• 2000

In the seismic migration, Kirchhoff and reverse time migration are used in general. In the reverse time migration using wave equation, two-way and one-way wave equation are applied. The approach of one-way wave equation uses approximately computed downward continuation extrapolator, it need tess amounts of calculations and core memory in compared to that of two-way wave equation. In this paper, we applied one-way wave equation to pre-stack reverse time migration. In the frequency-space domain, forward propagation of source wavefield and back propagration of measured wavefield were executed by using monochromatic one-way wave equation, and zero-lag cross correlation of two wavefield resulted in the image of subsurface. We had implemented prestack migration on a massively parallel processors (MPP) CRAYT3E, and knew the algorithm studied here is efficiently applied to the prestck migration due to its suitability for parallelization.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.1-13
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• 2022

For surveying shallow gas reservoirs in the Pohang basin, we proposed a seismic exploration method applicable to the transition zone in which land and marine areas are connected. We designed the seismic acquisition geometry considering both environments. We installed land nodal receivers on the ground and employed vibroseis and airgun sources in both land and marine areas. For seismic exploration in the transition zone, specific acquisition and processing techniques are required to ensure precise matching of reflectors at the boundary between the onshore and offshore regions. To enhance the continuity of reflection events on the seismic section, we performed amplitude and phase corrections with respect to the source types and applied a static correction. Following these processing steps, we obtained a seismic section showing connected reflectors around the boundary in the transition zone. We anticipate that our proposed seismic exploration method can also be used for fault detection in the transition zone.

• Proceedings of the Korea Contents Association Conference
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• 2016.05a
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• pp.163-164
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• 2016

실용음악 산업 분야는 비약적인 기술력의 발전이 있었지만 그런 기술력이 실용음악 교육에 적극적으로 적용되지 않고 있다. 본 논문에서는 음악 산업현장에서 음원 콘텐츠 제작 시 보컬리스트의 음정 보정을 위해 개발된 오토 튠(auto tune) 기술을 활용하여 가창 연주 시 음정과 박자에 관한 실시간 피드백을 시각적으로 학습자에게 제공하는 방식의 학습법을 개발했다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.80-84
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• 2006

센서 네트워크에서 노드들의 위치 인식에는 여러 가지 기법이 이용된다. 그 중 소리를 이용한 위치인식 기법은 정확도가 높고 넓은 지역에서도 활용이 가능하다는 장점이 있다. 소리를 이용한 위치 인식 기법은 음원으로부터 노드까지의 거리 정보 수집을 통하여 위치 인식이 가능하다. 하지만 기존의 기법에서는 거리를 정확하게 측정을 하는 것에만 초점이 맞춰져 있었으며 위치인식에 필요한 정보의 부족으로 위치인식 과정을 진행시키지 못하는 경우에 있어서는 고려를 하고 있지 않다. 본 논문에서는 소리를 이용한 위치인식 과정에서 발생할 수 있는 에러 보정 기법을 제안한다.

• Geophysics and Geophysical Exploration
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• v.5 no.1
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• pp.18-22
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• 2002

As a single arrival traveltime, maximum energy arrival traveltime has been known as the most proper operator for Kirchhoff migration. In case of the model having the simple structure, both the first arrival traveltime and the maximum energy arrival traveltime can be used as the correct operators for Kirchhoff migration. However for some model having the complex and high velocity contrast structure, the migration using the first arrival traveltime can't give the correct depth section. That is, traveltime to be required in Kirchhoff migration is the maximum energy traveltime, but, needs considerably more calculation time than that of first arrival. In this paper, we propose the method for calculating the traveltime approximated to the maximum energy arrival using one-way wave equation. After defining the WAS(Wrap Around Suppression) factor to be used for calculating the first arrival traveltime using one-way wave equation as the function of lateral grid interval and depth and considering the delay time of source wavelet. we calculate the traveltime approximated to the maximum energy arrival. to verify the validity of this traveltime, we applied this to the migraion for simple structure and complex structure and compared the depth section with that obtained by using the first arrival traveltime.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.94-100
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• 2001

In October 1997, low-frequency reverberation was measured at an experimental site off the west coast of the Jeju island using the explosive charge, Signals Underwater Sound (SUS). Received signals were separated into the noise, the reflection, and the scattering region, and then were analyzed for the spectral and statistical characteristics of each region. In the analysis of the spectrum we verified that each region had a unique frequency band and statistical characteristics as well. The results of this analysis showed that the real and imaginary portions were shown to be both normal distributions in each frequency bin. The reverberation envelope had a Rayleigh distribution and the phase had a uniform distribution.