• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.288-291
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• 2004

The Helmholtz resonator is one of noise control elements widely used in many practical applications. However the resonator array system, which is sometimes used to reflect or absorb low frequency noise, has not been well studied. We have investigated the difference in sound absorption of the Helmholtz resonator array panel caused by change in the resonator arrangement. Experiments and numerical calculations for various Helmholtz resonator array panels are carried out and the results are compared each other. The comparisons show that the acoustic coupling between closely located resonators affects the performance of the sound absorbing system. Particularly, the distance between resonators has a significant effect on the broadness of the sound absorption coefficient.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.97-100
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• 2005

Precise prediction of resonance frequency has been the subject of numerous papers related to Helmholtz resonator design because of its high performance at the frequency. The resonance frequency is dependent upon not only the internal dimensions of resonator but also the external boundary conditions such as the existence of other resonators in Helmholtz resonator array panel. However, the latter effect, which changes the external end correction of resonator, has not been well studied. We propose a formula to calculate the radiation impedance (or external end correction) of Helmhoitz resonator array panel. Any distance between adjacent resonators and any angle of Incidence can be allowed in the method. Numerical examples show how and how much the distance affects the resonance frequency of the panel. It is also found that the maximum absorption of the panel varies with the resonator arrangement.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.924-930
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• 2005

Sound absorptive materials have good performance in high frequency range, not at low frequencies. Therefore it has been great challenge to develop a sound absorbing structure that is good at low frequency. We propose to use a Helmholtz resonator array panel for this purpose. A Helmholtz resonator is one of noise control elements widely used in many practical applications. The resonator is a simple structure composed of a rigid-walled cavity with a neck, but it has very high performance at resonance frequency. This paper discusses the sound absorption of Helmholtz resonator array panels at normal and random incidence. First, various experimental results are introduced and studied. Secondly, we theoretically predict the absorptive characteristics of the resonator away panel. The theoretical approach is based on the Fourier analysis for a periodic absorber. We believe that this method can be used to design a panel for low frequency noise control.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.975-982
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• 2004

Helmholtz resonator is used to reduce noise of the narrow frequency band. It has high transmission loss at its resonance frequency. The silencer that combines many resonators could control broadband noise at low frequency. To convey this rather simple idea, serial and parallel arrangement of resonators have been tested to obtain high transmission loss characteristics in the band of which are selects. Theoretical and experimental results explain these characteristics in the absence of mean flow. The change of acoustic characteristics by the resonance frequencies and resonators arrangement are explained by using the equivalent Impedance analysis that is defined in this paper. It shows that the transmission loss has a maximum value when the separation distance between each resonator is λ/4 of its wavelength.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.521-524
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• 2005

To protect a satellite and electronic equipment from the acoustic loads generated by rocket propulsion system, many launch vehicle use acoustic blanket. Most high frequency region of the acoustic loads is reduced by nose fairing skins and acoustic barrier, but low frequency region is not. In order to control low frequency acoustic mode, we designed away resonator panel which was made of composite materials. This paper shows the absorption coefficient measurement result of resonator and SPL(Sound Pressure Level) reduction by using resonators in a rectangular cavity for experiment. Proper arrangement of acoustic resonators at each mode reduce effectively SPL around the satellite through changing boundary condition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.942-943
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• 2012

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.202-206
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• 2001

In this paper a novel dielectric resonator (DR) bandpass filter (BPF) with flexible arrangement of attenuation poles is proposed. This DR filter is similar to a conventional DR filter except adding a microstrip line below a DR, which not only shifts the location of attenuation poles, but also improves skirt characteristics. The duplexer with the proposed DR BPF has been yielded better isolation and sharper skirt behavior than that with a conventional DR alter. The implemented duplexer has shown a good performance and been well agreed with the simulation.

• ETRI Journal
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• v.31 no.3
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• pp.315-317
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• 2009

In this letter, a novel antenna with a miniaturized aperture is proposed. The substrate including a split-ring resonator array is inserted into a size-reduced open-ended waveguide. For a low return loss and high radiation efficiency, the ring arrangement is optimized, and a stepped transition using H-plane discontinuity is proposed. The proposed antenna achieves a 70% aperture reduction compared to a conventional standard waveguide antenna of WR-187 (47.6 mm${\times}$22.2 mm). The return loss drops significantly at three frequencies, and a reasonable gain is achieved. The aperture-miniaturized antenna can be used in many antenna applications such as near-field measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.178-183
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• 2003

This paper deals with transmission loss characteristics of the panel type silencer to control low frequency noise. The panel type silencer is composed of many Helmholtz resonators by side branch. Each resonator has high transmission loss on the narrow band of its resonance frequency. Direct arrangement of the resonators increases mainly the magnitude of transmission loss. If we arrange the resonators in a row, the peak and band of transmission loss are increased. This makes the resonator array to have high transmission loss in the broader band. Using this idea, we design a silencer that has broader band characteristics and smaller volume.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.496-505
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• 2020

In the previous research, the effectiveness of resonator was confirmed through the numerical analysis on two cases with the use of existing resonator at the Mukho and Imwon ports located in the eastern coast of South Korea by discussing the reduction rates of 1983 Central East Sea tsunami, and 1993 Hokkaido Southwest off tsunami, respectively. In this study, the reduction rates of tsunami height with three different resonators, Type I, II-1, and II-2, at the Samcheok port were examined respectively through the numerical analysis using COMCOT model under the same condition as the previous study. It was discussed the spatial distribution of maximum height of tsunami, change of water level, and effectiveness of resonator with the presence of new types of resonator, and change of their sizes. As a result, the effectiveness of resonator was verified through the application of new types of resonator reducing about maximum 40% of tsunami height. In order to design the optimal resonator for the variety of site condition, it is necessary to research about the various cases applying different shape, arrangement, and size of resonator as further study.