• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.692-693
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• 2004

We introduce a new velocity sensor, micro-flown sensor, which was developed by H-E de Bree. The sound absorption coefficients of a fiber material with the conventional pressure microphones and the micro-flown sensors were measured and compared. The experimental results show that both sensors could be well applied to measure the sound absorption coefficient but the pressure sensor was rather stable than micro-flown sensor

• 한국정밀공학회지
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• 제23권4호
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• pp.60-66
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• 2006

For the purpose of finding out the sound field characteristics in a rectangular cavity, analytical and experimental studies are performed with white noise input. Two-microphone impedance tube method is used to measure the impedances of foamed aluminum. Foamed aluminum is well known metallic porous material which has excellent properties of light weight and high absorbing performance. And predicted impedances of foamed aluminum are compared with measured impedances. The predicted acoustical parameters are applied to the theoretical analysis to predict sound pressure field in the cavity. The measured sound absorption effects are compared with the predicted values for both cases with and without foamed aluminum lining in the cavity of the rectangular enclosure.

• Composites Research
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• 제28권6호
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• pp.389-394
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• 2015

팽창된 그라파이트 인터칼레이션 컴파운드에 에폭시 수지를 주입하여 제조한 복합재료의 흡 차음성을 연구하였다. 관내법을 이용하여 복합재료의 흡음률과 음향투과손실을 측정하였다. 주사전자현미경을 이용하여 에폭시 매트릭스 내부에 그라파이트 인터칼레이션 컴파운드가 무질서한 방향으로 균일하게 분산된 것을 확인하였다. 그라파이트 인터칼레이션 컴파운드 함량이 증가함에 따라 복합재료의 면밀도가 감소하였으며, epoxy/(GIC 20 wt%) 복합재료의 면밀도는 순수 에폭시에 비하여 56% 감소하였다. 500~1000 Hz 주파수 영역에서 복합재료의 흡음률은 순수 에폭시에 비해 3배 정도 증가하였다. 그라파이트 인터칼레이션 컴파운드의 함량이 증가함에 따라 복합재료에 포함된 기공의 비율이 증가하여 순수 에폭시에 비하여 복합재료의 음향투과손실이 감소하는 것으로 판단된다.

• 대한기계학회논문집B
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• 제34권11호
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• pp.1027-1033
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• 2010

2상유동(기체-액체) 현상은 전자기발전, 원자력발전, 철강산업 등 유체 시스템에 자주 나타나는 현상으로, 2상유동을 파악하는 것은 유체 시스템의 안정성 및 성능을 위해 중요하다. 2상유동 특성 중 기공률은 압력강하와 열전달 성능을 결정하는 주요 인자로서 이를 측정하는 기술이 특히 중요하다. 유동의 임피던스를 측정하여 기공률을 산정하는 임피던스법은 전기적 특성을 이용하기 때문에 반응속도가 빨라 실시간 측정이 가능하며, 유동관 벽에 전극을 설치할 경우 유동 교란없이 측정할 수 있는 장점이 있다. Coney는 원형관에 적용할 수 있는 ring 임피던스미터를 이론적 연구하였다. 본 연구에서는 Coney가 이론적으로 제안하고 실험적으로 검증하지 못한 3-ring 임피던스미터의 유체 전기전도도에 대한 독립성을 실험적으로 검증하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.112-120
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• 2008

Today, the use of a vacuum cleaner gave us the higher quality of life than past time, but sometimes made us w1comfortable in the house because of the specific noise that is annoying. So we need to study how sound absorbtion materials affect sound power level and sound quality with sound metrics. In this paper, we will measure and calculate sound power level for vacuum cleaner and analyze characteristics of the noise for 10 Signals according to materials positioned in vacuum cleaner. The multiple regression analysis can estimate the nonlinear characteristics of relation between subjective evaluation and sound metrics. So we will develop sound quality index for vacuum sound.

• Journal of Forest and Environmental Science
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• 제40권2호
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• pp.90-98
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• 2024

This study analyzes the characteristics of sound-absorbing materials made from forest by-products of the deciduous tree species Zelkova serrata (Z. serrata) by evaluating their sound absorption performance. Accordingly, sound-absorbing materials with varying sample thicknesses, leaf sizes, and drying conditions were fabricated. The sound absorption properties were measured using the impedance tube method via middle-type measurement tube (100 Hz-3,200 Hz). The sound absorption properties were evaluated using the average sound absorption coefficient (ASAC), which was calculated from the measured sound absorption coefficients at 250 Hz, 500 Hz, 1,000 Hz, and 2,000 Hz. The ASAC value significantly improved as the leaf size increased to 0.5×0.5 cm², 1.0×1.0 cm², and 2.0×2.0 cm². The ASAC values under the two drying conditions were similar. There was no significant difference in ASAC according to the leaf size under the air-dried leaf condition, with a thickness of 2.50 cm. The highest ASAC value according to the sound-absorbing material thickness was 0.47 at a thickness of 2.50 cm and leaf size of 2.0×2.0 cm² under the air-dried leaf condition. In addition, the variation in ASAC was 0.23, indicating that the sound absorption performance according to leaf thickness was more significant than the difference in absorption properties according to leaf size. A sound absorption coefficient (SAC) of 0.4 or higher was observed across the measurable frequency band (100 Hz-3,200 Hz). Furthermore, the SAC values with respect to leaf size and thickness were close to 1 in the high-frequency range above 2,000 Hz. Therefore, it is considered that sound-absorbing materials using Z. serrata leaves are advantageous in the field of absorbing noise in a high-frequency band of 2,000 Hz or more, and it is better to manufacture a thickness of 2.50 and 2.0×2.0 cm².