• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
• /
• pp.735-740
• /
• 1998

Acoustic performance of DICT's acoustic laboratory was evaluated. As a result, background noise and inverse squre law of an anechoic room were satisfied with ISO 3745 standard value. Also, reverberation time and standard deviation of sound pressure level distribution in reverberation rooms were within maximum error limit that was ruled on ISO 3741.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.1198-1201
• /
• 2006

ISO 140-1 recommends installing diffusing elements in the room if there are large variations of the sound pressure level caused by strong standing wave. Also it requires that reverberation time should not be long or short. In accordance to this regulation, we adjusted the reverberation time in the range of $1{\sim}2$ sec by using 4 types of diffusing elements. This paper demonstrates how to balance the reverberation time in the range of $1{\sim}2$ sec by using several types of diffusing elements.

• 한국음향학회지
• /
• 제38권1호
• /
• pp.82-95
• /
• 2019

본 연구에서는 2015년 8월, 동해 동남방 해역에서 수행된 해양 잔향음 빔 데이터를 분석하였다. 잔향음 데이터는 이동하는 연구선에 의해 예인된 LFM (Linear Frequency Modulation) 음원과 삼중선 배열을 통해 수집되었으며, 신호처리 과정을 거친 이후 해저지형, 음원/수신기 수심, 음속구조에 따른 잔향음 준위의 변화를 분석하였다. 추가로 해저 잔향음의 확률적 특성을 해석하기 위해 셀 평균화 알고리즘이 적용된 정규화 데이터가 활용되었고, 모멘트 추정기법을 통해 형상 모수를 추정하여 해저 산란체의 확률적 특징을 확인하였다. 또한, 콜모고로프 스미르노프 검정 기법을 이용하여 데이터가 레일레이 분포와 K 분포 확률에 일치하는지를 분석하였다. 결과적으로 해저 지형에 따른 잔향음의 거리종속 특성과 음원/수신기 수심에 따른 시간 지연 및 세기 변화를 확인하였고, 잔향음에서 레일레이 확률분포와 유사한 특성을 관찰할 수 있었다.

• 한국음향학회지
• /
• 제25권8호
• /
• pp.389-394
• /
• 2006

중주파수 양상태 잔향음 준위는 음선이론을 사용하여 산출되었다. 제안된 알고리즘은 음파전달 경로 내 전방/후방 산란의 상호작용을 가정한다. 해양환경 (지형. 해저면 산란, 해수면 산란 등)은 거리 독립 해양환경으로 가정되었고 중주 파수 산란 모델이 사용되었다. 해상실험 자료를 사용한 알고리즘 검증 결과 양상태 잔향음 모델 알고리즘이 관측 해역의 양상태 잔향음 특성을 잘 반영하고 있음을 확인하였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2010년도 추계학술대회 논문집
• /
• pp.586-591
• /
• 2010

The sound field can be classified to the direct and reverberant sound field. If the sound absorption material in a room is not applied sufficiently, the reverberant sound field increases and the sound pressure in a room also increases when the sound source exists in a room. Therefore, the reverberation time should be controled in order to reduce the reverberant sound as well as sound pressure level in a room. Even though the reverberation time is specified and researched widely in architectural engineering, it is rarely performed in a marine engineering. Therefore, in this research, the reverberation time in a navel vessel is researched related to the noise reduction in a cabin.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 추계학술대회논문집
• /
• pp.492-497
• /
• 2006

This study gives the results of the measurements and analysises of the reverberation times in a small room such as apartment houses. We measured the RT by changing measurement conditions, which were sound sources. sound source's positions, receiving point & height, sampling time and so on. The critical factor affecting reverberation time was sound source in unoccupied houses and the reverberation time differences between result of RT using impulsive and interrupted sound source was 0.3sec at 500Hz frequency. And the difference of RT due to sound sources affected the sound insulation such as apparent sound reduction index and sound level difference about 1dB at each frequency in unoccupied houses.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.686-689
• /
• 2005

This study aims to analyzed the acoustics characteristics of Korean Traditional Houses in Chonnam Province varied with lay out and floor plane to reflect the way of control for environmental condition. These houses are surveyed the reverberation time and level difference between rooms of the main living room and other main floored room, master room and kitchen. As a result, the reverberation time of traditional rooms are below 0.6 second, and the sound insulation performance of Korean traditional door are mostly very low grade with D-15. The level difference between rooms are low grade not to meet minimum class except between main living room and master room away from main living building.

• 한국군사과학기술학회지
• /
• 제24권2호
• /
• pp.228-236
• /
• 2021

In order to understand the underwater noise source factor of the linear pump type forced ejection system, a reduced-model compressed water experiment device was developed. The reduced-model compressed water experiment device consists of a reverberation tank, a linear pump type forced ejection device, and an underwater vehicle. The underwater noise source was selected from the hydraulic ram moving speed, the hydraulic ram/piston pipe spacing, the ejection pipe inlet/water ram area ratio, and the number of water ram inlets. The underwater vehicle was ejected into the reverberation tank by the device. The source level was derived from the measured sound pressure. The source level tends to increase as the hydraulic ram/piston tube spacing and the hydraulic ram moving speed increase. The source level tended to increase as the area ratio was increased, but the level was weak. The number of water ram inlet did not affect the source level.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 춘계학술대회 논문집
• /
• pp.141-144
• /
• 2014

In urban spaces surrounded by buildings, trees could disperse sound energy, which affect sound level distribution and street canyon reverberation. Therefore, this paper examines the amount of scattered sound energy from a tree in open field by means of a reverberation time (RT). Five trees of different species and crown sizes were considered. The influential factors include crown size and shape, foliage condition, and source-receiver distance. The results show that RT is proportionally increased with the increase of tree crown sizes, which is the most determining factor. The maximum RT measured was 0.34 sec at 4000 Hz for the studied trees in leaf. The presence of leaves increased RT at high frequencies, typically by 0.14 sec at 4000 Hz. With increasing source-receiver distance within 40 m, RT was slightly changed.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.1026-1031
• /
• 2003

A vibration isolation system fur a large reverberation chamber (1,228㎥, 1,000ton) has been installed. The reverberation chamber generates loud noise and induces high level of vibration to perform spacecraft acoustic environmental tests. The isolation system prevents vibration transfer from the chamber to enclosure buildings. This paper describes logical design process and commissioning experiments of the system. Design criteria have been induced from rigid body model of the chamber. Finite element model has been employed to select the characteristics of rubber pads. A total of 21 rubber pads have been installed between the chamber and supporting pedestals. A sand bag of 800kg was dropped on the chamber floor to measure the natural frequency of the isolation system. Absolute transmissibility has been measured while generating 145㏈ in the chamber. The natural frequency of the chamber is 10.5㎐, which is 80% of estimated value. Overall transmissibility at working frequency range (25㎐-10,000㎐) is less than -6㏈.