• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.276-283
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• 2018

The purpose of the study is to identify a sound generating organ that has a major influence on the central frequency of the cicadas with the Helmholtz resonator structure for the first time. The sound of cicadas Cryptotympana atrata and Hyalessa fuscata were recorded and analyzed, then the motion of the tymbals was analyzed with a high-speed camera to compare the relationship between the frequency of sound and the motion of the tymbals. As a result, there was little difference in the frequency distribution of calling song and scream for two species. The tymbals of C. atrata oscillated in three vibration modes, while those of H. fuscata oscillated in one mode. There was no difference in the frequency of both tymbals of both cicadas, and three vibration modes of C. atrata generated sound with different frequency bands. The frequency band of tymbals and the central frequency band of calling song were very similar. In conclusion, it is presumed that the frequency of the cicadas with the Helmholtz resonator structure was determined by mode frequency of the tymbals than resonance condition of the abdomen.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.487-493
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• 2004

This study was conducted to develope a capacitive micromachined ultrasonic transducer (cMUT) which enable to high efficient non-contact transmit and receive the ultrasonic wave in air. Theoretical analysis and finite element analysis of the behavior of membrane (such as resonance frequency, membrane deflection, collapse deflection and collapse voltage) of the cMUT were performed. The design parameters of the cMUT such as the dimension and thickness of membrane, thickness of sacrificial layer, thickness and size of electrode were estimated. The resonance frequency of the membrane increased as the thickness of the membrane increased but decreased as the diameter of the membrane increased. The deflection of the membrane increased as d-c bias voltage increased. The collapse voltage of the membrane was analyzed.

• Proceedings of the Membrane Society of Korea Conference
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• 1998.10a
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• pp.19-30
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• 1998

1. 서론 : 그동안 막분리공정 기술이 이십년 여러산업 분야에서 사용되어 오면서 새로운 막제조 기술 및 적용 또한 발전을 하여 오고 있다. 막분리기술이 폭넓게 사용을 되어오고 있지만 높은 투자비 (특히 저용량일 경우), 운전비용 그리고 막의 오염 등으로 국내의 대부분 적용업체가 적잖은 문제를 경험을 하여왔다. 특히 막의 오염은 잦은 화학세정과 교체비용의 부담이 가져다 준다.(생략)

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.1-7
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• 2007

This paper presents a study on acoustic characteristics and sound generation mechanism of Cryptotympana atratas' songs which cause noise problems in summer days. The waveforms & FFT of Cryptotympana atratas' songs in nature were analyzed, and the actions of tymbals were visualized by the high speed camera. In order to know resonance frequency of the abdominal cavity of male Cryptotympana atrata, the sine sweep test was done. It was observed from the experimental results that Cryptotympana atrata's two tymbals act asymmetrically with respect to time & shape, and make a variety of frequencies every time it vibrates. It was also shown that Cryptotympana atratas' have a structure that cause resonances sounds only in a $7{\sim}7.5 kHz$ bandwidth.

• Journal of KSNVE
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• v.9 no.1
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• pp.14-24
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• 1999

현, 판, 막의 진동을 이용하는 피아노, 실로폰, 드럼, 북 등의 악기류를 제외하고는 일반적으로 구조물의 진동은 억제 대상이며 최근에 와서는 이에 관련된 환경 소음 및 진동에 대한 규제가 더욱 강화되는 추세이다. 그러나 자원 및 에너지 소비의 절감을 통한 제품단가의 인하뿐만 아니라 폐기물의 감소등 환경오염의 예방차원에서도 제품의 경량화가 지속적으로 추진되고 있고, 또한 제품성능에 대한 소비자의 기대는 상대적으로 저렴한 가격에 동일하거나 더 높아짐으로써 진동제어 문제가 더욱 부각되고 있다.(중략)

• Proceedings of the Membrane Society of Korea Conference
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• 1999.10b
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• pp.120-123
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• 1999

• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.63-72
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• 2008

One of the most important matters in keeping membrane structures in healthy condition is to maintain the proper tension distribution over the membrane. However, it is not easy to know the real stress level in the membrane quantitatively after completion of the structures. Authors suggested measurement method that can measure membrane stress using sound wave, and have been holding experimental tests of membrane stress measurement that used the sound external excitation with sine wave and white noise. The concept of the method is the fact that measurement of resonance frequency by vibrating membrane having rectangular boundary by audible frequency can measure membrane stress indirectly. In this paper, through the experimental tests it is proved that the equipment can be used for not only the membrane material of type A but also for types B and C. In addition, it is proved that the developed measurement equipment is available to stably measure the membrane stress which exists in the membrane material of the actual membrane structures.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05b
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• pp.94-97
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• 2004

수처리를 위한 분리막은 정수, 하수 및 오폐수 처리등 그 사용이 나날이 증가하고 있고, 막분리 공정의 경제성을 결정하는 막오염에 대한 연구가 활발히 이루어지고 있다. 분리막 표면의 오염 물질을 제거하기 위하여 표면유속의 증가, 분리막 회전, 진동 등에 의한 물리적 방법들이 사용되었고, 특히 근래에는 시설의 단순화 등을 이유로 침지형 모듈 이용이 증대되고 있으며[1] 특히 단위면적당 높은 막면적을 갖는 중공사막 침지형 모듈의 이용이 증가하고 있다.(중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.298-302
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• 2002

Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.540-568
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• 2006