• Explosives and Blasting
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• v.18 no.2
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• pp.14-22
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• 2000

The estimation of proper prediction method and the alteration of transformation method of environmental regulation standard were carried out by measuring blasting noise in construction field. The correlation of scaled distance with sound pressure level were better than with sound level, but it was proved to be difficult to control blasting noise because the correlation factor was too 1ow. three methods to transform sound pressure levee to sound level were examined. The method is the transformation by correlation equation of sound pressure level and sound level which are measured at the same time, and simplified transformation of A-weighting network corresponding to dominant frequency, and the transformation of sound pressure level by FFT. There were many errors to transform. The best effective method is the transformation using correlation equation of sound pressure level and sound level which are measured at the same time.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.584-588
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• 2021

The impedance of the speaker is likely to be recognized as a fixed value. However, speaker impedance continues to vary with frequency variation, especially larger in resonant frequency region. The sound pressure level of loudspeakers is determined by the current flowing throughout the coil that consists loudspeakers. If loudspeakers are driven by voltage, sound pressure level of the loudspeaker is distorted by the variation of loudspeaker impedance. Current-drive of loudspeakers can solve this problem, but distortion of sound pressure level occurs in low frequencies due to resonance. The distortion can degrade the sound quality of the sound system. So to solve this problem, In this paper, we propose a resonance compensation circuit using DSP. we simulates audio systems using an equivalent model of loudspeakers to verify distortion of sound pressure level due to impedance variation and propose a circuit to compensate it. The proposed circuit is configured using a state variable filter and it can adjust the center frequency and output, so it will be used various sound systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2586-2594
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• 2010

A pure tone audiometer should be able to produce both pure tone and masking noise with exact sound pressure level and frequency. For such purpose, it is unavoidable to periodically calibrates pure tone audiometer. However, manual acoustic calibration requires not only attention but also long time. It is possible to execute automatically calibration using software if it is PC-based pure tone audiometer. In this paper, we describe auto-calibration software for PC-based pure tone audiometer and dedicated sound level meter which has been implemented upon PC by us. To verify auto-calibration module, we examine whether output of PC-based audiometer calibrated through auto-calibration of this paper satisfies RETSPL of IEC or not.

• Economic and Environmental Geology
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• v.48 no.5
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• pp.379-390
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• 2015

Multibeam backscatter strength is dependent not only on seafloor sediment facies but also on changed incidence angle due to the actual bottom slope. Therefore, the correction for actual bottom slope should be considered before the analysis of backscatter strength. This paper demonstrates the backscatter correction technique for the actual incidence angle and ensonified area. The target area is a part of the eastern Yellow Sea with water depths of 46~55 m. The area is located between the sand ridges and covered by large dunes with various bottom slopes. The dunes usually have the gentle slopes of about $1{\sim}3^{\circ}$, but show some steep slopes of $5{\sim}15^{\circ}$ on the crest. The backscatter strength values on the crest range from -34 to -23 dB, assuming that the bottom is flat. However, this study shows that the backscatter strength range was somewhat reduced (-32~-25 dB) after correction for actual bottom slope. In addition, the backscatter imagery was significantly improved; high and low backscatter strength values on the crest due to the actual bottom slope were normalized. The results demonstrate that the correction technique in this study is an effective tool for processing backscatter strength.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.137-140
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• 1999

본 논문에서는 디지털 보청기의 자동보정법을 제안하고 이를 이용하여 구현한 보정시스템에 대하여 기술한다. 일반적으로 난청환자의 청각 손실은 전 주파수를 걸쳐 일정하게 발생하는 것이 아니라, 고음 또는 저음 등 일부 특정 주파수 대역의 청각특성의 이득이 다른 주파수에 비해 상대적으로 낮아져서 생기는 현상이다. 그러나 현재까지의 보청기는 이와 같은 청각 손실을 가지고 있는 환자들에 대하여 전 주파수 대역의 음압을 동일 비율로 높여주는 문제가 있다. 이와 같은 보청기로 보정하게 되면, 주파수 대역별 균형이 맞지 않기 때문에 소리가 변형되어 들리게 되고, 명료도 또한 떨어지게 된다. 또한, 기존의 아날로그보청기는 생산공정 중에 잡음 피크 제거, 리미터 조정, 이득 조정(GC) 등의 작업을 수동으로 수행하게 되는데, 이는 작업공정이 복잡하고 개개인에 청각특성에 맞는 정확한 보정이 불가능한 문제점을 안고있다. 이와 같은 문제점을 해결하기 위하여 제안한 자동보정 시스템은 각 주파수 대역별 최적화된 파라미터를 자동적으로 찾아서 입력하므로 보다 정확하고 신속한 보정이 가능하게 된다. 이 시스템은 외부 IC 콘트를 장치인 Hl-PRO를 이용하여 PC 환경 하에서Visual Basic으로 구현하였으며 시스템의 출력값을 측정하여 검토한 결과 구현한 자동보정법이 유효함을 확인할 수 있었다.

• Korean Journal of Remote Sensing
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• v.17 no.1
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• pp.45-56
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• 2001

To acquire seabed information, the mosaic images of the seabed were generated using Side Scan Sonar. Short time energy function which is needed for slant range correction is proposed to get the height of Tow-Fish to the reflected acoustic amplitudes of each ping, and that leads to a mosaic image without water column. While generating mosaic image, maximum value, last value and average value are used for the measure of a pixel in the mosaic image and 3-D information was kept by using acoustic amplitudes which were heading for specific direction. As a generating method of mosaic image, low resolution mosaic image which is over 1m/pixel resolution was generated for whole survey area first, and then high resolution mosaic image which is generated under 0.1m/pixel resolution was generated for the selected area. Rocks, ripple mark, sand wave, tidal flat and artificial fish reef are found in the mosaic image.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1157-1164
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• 2007

In this paper, we implement a PDA(Personal Digital Assistant)-based audiometric system in order to estimate hearing threshold by adopting both pure-tone sound and speech audiometric test system. To estimate a subject's hearing threshold in an ambulatory audiometric test environment, an efficient sound calibration scheme between a PDA and a headphone device is proposed by appling polynomial fitting algorithms in 8-banded frequency ranges.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.1
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• pp.35-39
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• 2001

Multibeam echosounder data, collected to investigate seabed features and topography, are usually subject to outliers resulting from the ship's irregular movements and insufficient correction for pressure calibration to the positions of beams. We introduce a statistical method which adjusts the outliers using the ARMA (Autoregressive Moving Average) technique. Our method was applied to a set of real data acquired in the East Sea. In our approach, autocorrelation of the data is modeled by an AR (1) model. If an observation is substantially different from that obtained from the estimated AR (1) model, it is declared as an outlier and adjusted using the estimated AR (1) model. This procedure is repeated until no outlier is found. The result of processing shows that outliers that are far greater than signals in amplitude were successfully removed.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.397-400
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• 2004

소음원 또는 방사음장을 가시화하기 위하여 소음원을 둘러싸는 한 면에서의 음압측정을 통해 임의의 3차원 공간상의 음향 물리량을 예측하는 음향 홀로그래피 방법이 사용되고 있으며 이때 반사파가 존재하지 않는 기본 가정을 만족해야 한다. 반사파가 존재하는 경우에는 반사파를 보정하거나 또는 반사파의 음장이 미치는 영향이 무시할 만큼 작다고 가정하여 음장 예측이 가능하게 된다. 최근 해양연구원에서는 음향 홀로그래피 방법을 이용하여 수중음장을 가시화하는 시스템을 개발하였으며 시스템 검증을 위해 무향수조 내 단순음원을 이용하여 음장예측을 수행하였다. 무향수조 표면에는 흡음처리가 되지 않아 표면 반사파가 존재하나 해석 결과 반사파의 영향이 작은 경우에는 반사파를 무시하고 음장해석의 수행이 가능함을 확인하였다.

• 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.