• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.837-842
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• 2000

Reverberation time is the well known theory and widely used in commercial apparatus to get reverberation time. However large fluctuation in low frequency region occurs in a small cabin due to superposition of a few modes. This paper investigates this phenomena in terms of modal density in frequency domain and suggests a method to get lower limit of reverberation time using the integration of the time-SPL diagram. The suggestion is confirmed by simulation and shows reasonable results to get lower limit of reverberation time and maximum absorbing power in the cabin.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.34-40
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• 2008

Acoustic design parameters of a half-wave resonator are studied experimentally for acoustic stability in a model chamber. According to the standard acoustic-test procedures, acoustic-pressure signals are measured. Quantitative acoustic properties of damping factor and sound absorption coefficient are evaluated and thereby, the acoustic-damping capacity of the resonator is examined. The diameter and the number of a half-wave resonator, its distribution, and the diameter of an enclosure are selected as the design parameters for optimal tuning of the resonator. Aroustic-damping capacity of the resonator increases with its diameter. When the open-area ratio of the resonator exceeds the optimum value, over-damping appears, leading to the decrease in the peak absorption coefficient and the broadening of absorption bandwidth. As the resonator diameter increases, optimum open-area ratio decreases.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.3
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• pp.215-221
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• 2017

Audiological rehabilitation by itself can provide satisfactory services through acquisition of background information on hearing loss, audiological evaluation, analysis of electroacoustic characteristics of hearing aids, and determining acoustic gain. However, hearing can be exacerbated, and sound pressure level of hearing aids can be lowered. Moreover, breakdown of hearing aids can happen. Therefore, the early detection of hearing loss and regular follow-up observations are very important. The aim of this study concern the direction of effective audiological rehabilitation by checking the clinical cases where hearing aids fitting failures were found.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.333-336
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• 2020

6 자유도 오디오 재현 기술은 사용자가 6 자유도를 가지는 콘텐츠 또는 응용에서 음향학적 주변 환경과 사용자의 위치에 맞는 오디오를 재현하는 기술로서, 가상 현실, 게임 등에 적용이 될 수 있다. 6 자유도 오디오는 기존의 고정된 위치에서 재생되는 채널 기반 오디오와는 다른 특징이 있어 오디오 재생 장치와 헤드폰 또는 스피커만으로 수행하던 기존의 오디오 청취 평가 방법으로 비교하고 평가하는 것이 불가능하다. 최근 MPEG 오디오 서브그룹에서는 6 자유도 오디오 재현 기술에 대한 표준화를 진행하고 있으며, 이를 평가할 수 있는 시스템도 함께 제시하고 있으며, 2019 년 12 월에는 제안한 시스템을 활용한 파일럿 테스트가 진행이 되었다. 본 논문에서는 MPEG 에서 진행한 파일럿 테스트 시스템과 평가 방법에 대하여 살펴보고, 본 기관에서 평가한 내용 및 결과에 대해 기술하며, MPEG 에서 제시한 평가 시스템이 6 자유도 오디오 재현 기술의 평가에 적절한지에 대한 의견을 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1259-1268
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• 2015

The sonic layer depth (SLD) variability is important for understanding the acoustic properties of the upper ocean that influence acoustic communications, acoustic tomography, and naval operations related to searching and detecting marine underwater vessels. Generally, the SLD is the acoustical equivalent of the mixed layer depth (MLD), although they are defined differently. In this study the SLD was compared with the MLD over the annual cycle in the East Sea using an available set of temperature-salinity observation profiles. For the comparison, various definitions and methods of the MLD had applied. As a result, the SLD in the East Sea is slight similar to the curvature method applied MLD, but the other MLD have severe differences with the SLD. Futhermore, a parabolic equation transmission model is used to evaluate the cutoff frequency trapped in surface duct. It follow that there is an optimum frequency for propagation at which the loss of sound is minimum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.97-100
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• 2004

물질의 진동감쇠 특성을 평가하는 대표적인 시험법은 ISO 6721, ASTM E 756 등에서 찾아 볼 수 있다. 이들 규격에서는 비접촉 가진방법으로 전자석 시스템을 사용한다. 하지만 이와 같은 방법은 강판 단독으로의 시험은 간편하나 비자성체 물질이나 도료를 도포 할 경우, 별도의 금속판이 필요하다. 또한 그에 따른 금속판의 감쇠특성을 별도로 평가해야 되며, 접착제에 대한 영향도 고려해야 된다. 이에 대한 보완으로 음압가진 방법을 이용한 비접촉 가진을 강철과 플라스틱에 적용하였다. 실험결과, 강철과 플라스틱의 공진주파수에 따른 손실계수와 탄성계수는 전자석을 이용한 실험결과와 일치하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.68-72
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• 2019

대하천사업으로 4대강에 다기능보 건설 및 대규모 준설이 이루어졌으며, 그 과정을 통해 인위적으로 변화된 하천지형은 시간이 경과함에 따라 유사공급과 유수흐름 등 다양한 요인들의 복합적 영향 하에서 지속적 변화과정을 거치게 된다. 따라서 하천의 효율적인 운영 및 관리를 위해서는 하천지형에 대한 연속적인 측정 및 분석을 통해 하천유로의 지형학적 특성과 그 변화의 양상과 정도를 파악하는 것이 필요하다. 본 연구에서는 낙동강 중 하류 구간에 대하여 음향측심기를 이용한 수심측량을 통해 유로의 지형정보를 취득 분석하여 다기능보 건설 후 유로의 지형학적 특성에 있어서의 변화 양상을 파악하고자 하였다. 이를 위하여 취득된 지형자료를 활용하여 유로 단면에 대한 기하학적 특성치들을 통한 형태학적 분석을 실시하였다. 또한 대하천사업 준공시 취득된 측량성과정보와의 비교를 통해 지형변화 양상과 정도를 파악하였다. 이를 통 해 대하천사업 이후 낙동강 중 하류 구간 유로의 지형변화 양상과 규모를 파악할 수 있었으며, 대하천사업 이후 준공측량성과를 기반으로 고시된 하천기본계획 상 지형정보의 정확성에 대해 평가할 수 있었다. 본 연구의 공간적 범위가 낙동강 중 하류 중 일부 구간들에 제한되었기에, 향후 본 연구에서 제안한 방법론을 활용한 지형특성 및 변화의 양상과 규모에 대한 지속적인 평가가 필요할 것으로 판단된다.

• 재활복지
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• v.22 no.1
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• pp.157-168
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• 2018

The purpose of this study is to investigate the impact of semi-closed vocal training-based Vocal Aerobic Treatment on the voice improvement of soprano. Study subject was one soprano who appealed to the suffering of her voice problem due to vocal cord nodule. A study method of conducting pre/post acoustic evaluation and subjective voice evaluation to compare the measures was used; Vocal Aerobic Treatment was carried out twice a week for a total of 32 session. In the acoustic evaluation, MDVP (multi-dimensional voice program) and VRP (voice range profile) were used to evaluate the pitch, voice quality, and voice range; in the subjective voice evaluation, SVHI (singing voice handicap index) was used to assess voice satisfaction. As a result of the pitch evaluation, the soprano maintained a proper Fo. As a result of the voice quality evaluation, the jitter, shimmer, and the noise harmonic ratio numbers decreased compared to the numbers shown before the treatment. As a result of the voice range evaluation, the scope of the range was broadened, with the number of semitone increasing from 30 to 35. As for the subjective voice evaluation, the result of the total score obtained after the survey report divided by the number of questions showed a decrease from 3.6 to 0.6. The soprano herself reported of having a minor extent of a voice problem. The summary of the above results reflects that Vocal Aerobic Treatment is useful in the voice improvement of vocalists However, as this study is case research regarding the Vocal Aerobic Treatment effect on one soprano, further research on the treatment effect covering many other vocalists is necessary. Also, there is a need for follow-up studies regarding voice management and voice treatment program on not only the vocalists but also the voice users in many other professions.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.157-161
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• 2016

The purpose of this study is that in measures the acoustic propagate characteristics and temperature sensitivity of ultrasound tissue mimicking phantom(TM phantom). TM phantom manufacture according to the International Electronical Committee(IEC) guidelines for acoustic propagate characteristics of soft tissue. TM phantom was observed to have the image brightness and the image depth penetration decreases changes convergence which was the subject of ultrasound image characteristics in accordance with an external temperature that the change is reduced in temperature below $22^{\circ}C$. This study provide a basis t o create another TM Phantom and TM Phantom has been determined that it is appropriate for use in more than $22^{\circ}C$.

• Phonetics and Speech Sciences
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• v.15 no.4
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• pp.45-51
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• 2023

Voice issues such as voice weakness that arise with age can have social and emotional impacts, potentially leading to feelings of isolation and depression. This study aimed to investigate the changes in acoustic characteristics resulting from aging, focusing on voice quality and spoken fluency. To this end, tasks involving sustained vowel phonation and paragraph reading were recorded for 20 elderly and 20 young participants. Voice-quality-related variables, including F0, jitter, shimmer, and Cepstral Peak Prominence (CPP) values, were analyzed along with speech-fluency-related variables, such as average syllable duration (ASD), articulation rate (AR), and speech rate (SR). The results showed that in voice quality-related measurements, F0 was higher for the elderly and voice quality was diminished, as indicated by increased jitter, shimmer, and lower CPP levels. Speech fluency analysis also demonstrated that the elderly spoke more slowly, as indicated by all ASD, AR, and SR measurements. Correlation analysis between voice quality and speech fluency showed a significant relationship between shimmer and CPP values and between ASD and SR values. This suggests that changes in spoken fluency can be identified early by measuring the variations in voice quality. This study further highlights the reciprocal relationship between voice quality and spoken fluency, emphasizing that deterioration in one can affect the other.