• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.862-866
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• 2002

High intensity vibro-acoustic testing is the appropriate method for flight qualification testing of space flight vehicle which must ensure the acoustic environment of launch. To qualify vibro-acoustic environment during its flight, High Intensity Acoustic Test was performed for KOMPSAT-2(Korea Multi-Purpose SATellite) STM(Structural Thermal Model). This paper presents the detailed description on the high intensity acoustic test for KOMPSAT-2. Additionally the test results was compared with the analysis ones, which were estimated with 3-D SEA(Statistical Energy Analysis) model.

• 한국광학회지
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• 제11권6호
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• pp.423-428
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• 2000

방향성 결합 구조의 음향파 도파로를 이용한 편광모드 변환형 파장가변 광 필터를 LiNbO$_3$ 와 Ti 이중 확산 공정기술을 이용하여 제작하였다. 균일 결합구조형 AOTF의 부모드의 크기를 두 음향파 도파로의 방향성 결합형 가중 결합 원리를 이용하여 8 dBwjd도 추가적으로 억제시킬 수 있었다. 1551.6mm 파장의 TE, TM 입사 편광모드와 173.58MHz, 17.78mW RF 구동신호각각에 대해서 -12.68dB 부모드 억압과 90% 변환효율이 측정되었다. 파장변화율과 통과 대역폭은 각각 8.86nm/ MHz, 1.7nm로 측정되었다.

• 한국음향학회지
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• 제13권5호
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• pp.40-50
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• 1994

본 논문에서는 3차원 음향 인텐시티 프로브의 고주파 영역에서 발생하는 감도 저하 현상을 보정하는 방법에 대해 연구하였다. 고주파 영역에서 측정오차는 음향 인텐시티 프로브를 구성하는 마이크로폰으로 수음한 신호들의 위상차로 인하여 발생한다. 이 오차는 마이크로폰 사이의 간격보다 측정대상 음향신호의 파장일 작을 경우, 즉 신호의 주파수가 높을수록 크게 발생한다. 이 연구에서는 두개의 마이크로폰으로 구성된 1차원 프로브의 보정법들을 제안하여 그 유효성을 컴퓨터 수치계산으로 검토하였다. 음향 인텐시티 프로브를 구성하는 마이크로폰 사이의 위상차를 음원의 추정된 방향으로 보정하는 방법이 가장 유용하였으며, 이를 3차원 프로브에 적용하여 임의의 방향으로 전파하는 음원에 대해 컴퓨터 수치계산으로 검증하였다. 그 결과, 4개의 마이크로폰을 60mm 간격으로 구성한 3차원 프로브로 1dB 이하의 정밀한 측정이 가능한 주파수 범위가 약 1.2kHz 이였던 것을 제안한 보정방법을 적용한 후, 약 2.8kHz까지 감도가 향상됨이 확인되어 제안한 보정법의 유효성이 증명되었다.

• 대한후두음성언어의학회지
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• 제8권1호
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• pp.12-17
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• 1997

Measuring phonatory stability using MDVP(Multi-dimensional voice program, Kay Elemetrics Corp., NJ, USA) are becoming popular in many Korean clinics and laboratories, yet questions about standardization and reference values have remained. The purpose of present study was to examine the effects of frequency and intensity variation on the results of acoustic analysis related to phonatory stability. Twenty young adults(ten females and ten males) were asked to sustain vowel /a/ for more than 3 seconds under 9 different pitch and loudness conditions. Using MDVP, nine voice samples were analyzed, and jitter percent, fundamental frequency variation, shimmer percent, peak amplitude variation, noise to harmonic ratio, amplitude tremor intensity index, and degree of subharmonics were compared. The results showed that intensity changes can significantly affect various phonatory stability measures, and the lowest perturbation values can be obtained from slightly louder(10dB) phonatory condition than comfortable level phonation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.629-632
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• 2005

What does sound look like if we can see it? It might depend on the acoustic variables we want to see. In this article, we propose various ways to visualize or express sound field in much more intuitive manner. In particular, new visualization schemes that can effectively visualize sound intensity and 3D pressure field are proposed. This allows us to represent sound pressure, particle velocity and acoustic conductance at the same time, even in three-dimensional coordinate. Visualization examples corresponding to the proposed techniques show that we can successfully transfer the meaning of physical variable to visual space.

• 한국음향학회지
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• 제13권3호
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• pp.41-50
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• 1994

이 연구에서는 3차원 음향 인텐시티를 동시에 측정할 수 있는 프로브를 이용하여 음향 인텐시티를 측정할 때 필연적으로 발생하는 오차를 컴퓨터의 수치계산으로 검토하였다. 이 3차원 음향 인텐시티 프로브는 Suzuki등에 의해 제안된 4개의 마이크로폰으로 구성된 것이고, 수치계산에서는 이상적인 점음원과 유한 크기를 가지는 면음원에 대해서 프로브의 각 축방향 및 임의의 방향에 대한 측정오차를 근거리 음장에서 분석하였다. 그 결과, 점음원의 경우 측정거리가 프로브를 구성하는 마이크로폰 사이의 간격보다 약 2.5배 이상 떨어진 거리에서 오차 1dB 이하의 정밀한 측정을 할 수 있었고, 유한 크기의 면음원의 경우, 면음원의 한 변의 길이가 0.02m이상일 때 근거리 음장의 측정오차가 크게 감소하기 시작하여, 한 변의 길이가 0.2m일 때 측정거리가 마이크로폰 사이의 간격보다 0.67배로 근접하여 측정하여도 1dB 이하의 정밀한 측정이 가능한 것으로 평가되어 이 프로브의 근거리 음장 측정의 유효성이 확인되었다.

• 한국음향학회지
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• 제3권1호
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• pp.3-8
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• 1984

By one dimensional acoustic transmission from ground to air, the author has derived the level of sound caused by earthquakes. He has also tried to assign proper values of ground acceleration to the modified mercalli intensity scale and thence earthquake sound level to the intensity scale has been deduced as L\sub M/ = 79.6+6.0M, dB, where M is the earthquake magnitude in the modified Mercalli intensity scale.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1078-1088
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• 2010

In order to analyze the quantitative characteristics of acoustic streaming, experimental setup of 3-D stereoscopic PIV(particle imaging velocimetry) was designed and quantitative ultrasonic flow fields in the gap between the ultrasonic vibrator and heat source were measured. Utilizing acoustic streaming induced by ultrasonic vibration, surface temperature drop of cooling object was also measured. The study on smart cooling method by acoustic streaming induced by ultrasonic vibration was performed due to the empirical relations of flow pattern, average flow velocity, different gaps, and enhancement on cooling rates in the gap. Average velocity fields and maximum acoustic streaming velocity in the open gap between the stationary cylindrical heat source and ultrasonic vibrator were experimentally measured at no vibration, resonance, and non-resonance. It was clearly observed that the enhancement of cooling rates existed owing to the acoustic air flow in the gap at resonance and non-resonance induced by ultrasonic vibration. The ultrasonic wave propagating into air in the gap creates steady-state secondary eddy called acoustic streaming which enhances heat transfer from the heat source to encompassing air. The intensity of the acoustic streaming induced by ultrasonic vibration experimentally depended upon the gap between the heat source and ultrasonic vibrator. The ultrasonic vibration at resonance caused the increase of the acoustic streaming velocity and convective heat transfer augmentation when the flow fields by 3D stereoscopic PIV and temperature drop of the heat source were measured experimentally. The acoustic streaming velocity of air enhancement on cooling rates in the gap is maximal when the gap agrees with the multiples of half wavelength of the ultrasonic wave, which is specifically 12 mm.

• 말소리와 음성과학
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• 제8권4호
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• pp.115-122
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• 2016

This study investigates the acoustic-phonetic features and speech intelligibility of Lombard speech in children with intellectual disability, by examining the effect of Lombard speech at 3 levels of non-noise, 55dB, and 65dB. Eight children with intellectual disability read sentences and played speaking games, and their speech were analyzed in terms of intensity, pitch, vowel space of /a/, /i/, and /u/, VAI(3), articulation rate and speech intelligibility. Results showed, first, that intensity and pitch increased as noise level increased; second, that VAI(3) increased as the noise level increased; third, that articulation rate decreased as noise intensity increased; finally, that speech intelligibility increased as noise intensity increased. The Lombard speech changed the VAI(3), vowel space, articulation rate, speech intelligibility of the children with intellectual disability as well. This study suggests that the Lombard speech will be clinically useful for the persons who have intellectual disability and difficulties in self-control.

• 비파괴검사학회지
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• 제10권2호
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• pp.56-62
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• 1990

Surface Acoustic Waves(SAW) are generated on silicon wafer and $YZ-LiTaO_3$ substrate and are detected by noncontact method. As wave sources two kinds of transducers are used : the wedge-type of 20.0 MHz and fabricated Interdigital Transducer(IDT) of 20.8 MHz. SAW are modulated by the optical chopper frequency and are syncronized with a laser beam. In signal processing, intensity variations of light due to the intensity of SAW are analyzed using lock- in amplifier. From the results, corresponding to the applied input power, the intensity variations of a deflected light by corrugations on the substrates are increased and saturation phenomenon is observed.