• The Journal of the Acoustical Society of Korea
• /
• v.12 no.3
• /
• pp.68-75
• /
• 1993

포락선 인텐시티는 신호의 진폭 변화에 비해 상대적으로 천천히 벼놔한다. 본 논문에서는 이러한 성질을 이용하여 종래의 순시 음향 인덴시티법을 수정한 새로운 포락선 인텐시티법을 제안하여 비정상 신호 해석에 이 기술을 적용하였다. 이 기술의 유효성은 반사체가 있는 무향실 내의 충격성 음원에 대해 수치계산 결과와 실험결과의 비교로부터 검증되었고 또한, 이 기술은 무향실 및 잔향실 내의 평판 타음 음원의 지향특성 해석에 응용되었다. 수치계산 결과 및 측정결과는 일치하였고, 제안된 방법은 종래의 순시 인텐시티법보다 특히 과도특성을 갖는 충격성 음원 분석에 보다 유효함이 확인되었다.

• The Journal of the Acoustical Society of Korea
• /
• v.26 no.6
• /
• pp.235-242
• /
• 2007

The test and evaluation of floor impact sound is mainly conducted before move in the residence. Floor impact sound generating is actually the conditions in which a heavy load like a curtain and furniture is installed, the situation before and after move in the residence is different. In this study, we investigate the floor impact sound variations according to the live load installation like furniture in the source room. The vibration acceleration level and floor impact sound level variation were measured before and after live load ($200kg/m^2$) installation in the floor impact sound test building and the field. The difference was not large although the vibration acceleration level and the floor impact sound level were reduced through measurement result of load installation. Resonance frequency was not changed by load installation.

• The Journal of the Acoustical Society of Korea
• /
• v.2 no.1
• /
• pp.27-34
• /
• 1983

음속 기울기가 부(-)의 약한 상태와 강한상태에 있는 천해의 두 해역에서 단일주파수의 지향성 음원과 광대역 충격음원 두 종류에 의하여 측정을 하였다. 음파가 처음 해저에 부딪치는 가까운 거리에 서의 Reverberation 은 ray tracing 에 의하여 입사각에 따라 power spectrum analyzer에 의하여 분석 되었으며 원거리의 경우 이론 모델로 계산된 값과 비교되었다. 이 때의 산란은 지향성에 산란상수 -24dB였다. 또한 산란강도는 주파수의 증가에 따라 완만한 증가를 나타내었다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.433-442
• /
• 2013

This paper presents experimental research work for the evaluation of one-dimensional and two-dimensional acoustic source locations with 50m length of a precast prestressed concrete box girder. Acoustic events are generated by the impacts of Schmidt Hammer and the impact signals are detected by acoustic emission sensors mounted on the concrete web surface of PSC box girder with the average spacing of 9.34m. Based on the amplitude of detected acoustic signals, considering the noises developed in PSC box girder bridges, the arrival times of acoustic signals are estimated by the first arrival times of 0Volt, 0.5Volt, and 1.0Volt amplitude in each signal. Using Least Square Method, the velocities and the source locations of acoustic signals are evaluated. Based on the test results, the spacing of AE sensors and the AE sensor networks are discussed to reduce the source location errors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.275-278
• /
• 2005

In this study, the dynamic properties of a floor impact sound isolation pad expressed in terms of the natural frequency, the dynamic stiffness per unit area and the loss factor are measured by the resonant method. By using the measured dynamic properties, the vibration transmissibility diagram is obtained for each isolation pad, which is compared with the values tested by the impact sound sources at the room in an apartment. From the comparative results, it is found that the noise reduction Performances. of isolation pads are closely connected with the natural frequency and the dynamic stiffness per unit area.

• Journal of Biomedical Engineering Research
• /
• v.24 no.5
• /
• pp.453-458
• /
• 2003

When the piezoelectric extracorporeal shock wave lithotripter is operated. sounds are generated. In this paper, we present a fact that the sounds are radiated undoubtedly from the object to be hit by the shock waves. For this results. we use the method to identify the sound source location of the radiated sounds by estimating the distance and the bearing from the sound source using one hydrophone. In addition. we investigate the relation between the radiated sounds and the vibrations of the objects using bronze models of disc type with clear vibrating characteristics and present the results of experiments to be analyzed.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.5
• /
• pp.369-377
• /
• 2018

This study investigated the effect of noise and reverberation on subjective measure of speech transmission performance for elderly person with hearing loss in residential space through listening test. Floor impact, road traffic, airborne, and drainage noise were employed as the residential noise, and several impulse responses were obtained through room acoustical computer simulation for an apartment building. Sound sources for the listening test consisted of residential noises and speech sounds for boh the young (the original sound) and the aged (the sound filtered out by filters with frequency responses of hearing loss of 65 years elderly person). In the listening test, subjects evaluated speech intelligibility and listening difficulty for the presented word ($L_{Aeq}$ 55 dB) at three noise levels ($L_{Aeq}$ 30, 40, 50 dB) and three reverberation times (0.5, 1.0, 1.5 s). Results showed that the residential space with noise level lower than equal to 50 dB ($L_{i,Fmax,AW}$) for jumping noise and 40 dB ($L_{Aeq}$) for road traffic, airborne, and drainage noise had speech intelligibility of 90 % and over and listening difficulty of 30 % and below. Speech intelligibility and listening difficulty for the aged sound source was shown to be 0 % ~ 5 % lower and 2 % ~ 20 % higher than those for the young sound source, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.1077-1082
• /
• 2001

기존의 타이어를 사용한 중량충격음에 대한 차음성능 평가방법의 타당성을 살펴보기 위하여 청감실험에 의한 감성적 반응결과와 L등급 및 Leq에 의한 평가 결과를 비교 분석하였다. 동일한 바닥충격원에 대한 분석결과 L등급평가 보다 Leq에 의한 평가가 청감실험의 반응에 잘 대응하는 것으로 나타났다. 또한, Zwicker parameters 중 Loudness와 Unbiased Annoyance는 청감실험과 가장 유사한 경향을 보였다.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2014.01a
• /
• pp.427-428
• /
• 2014

본 연구의 목적은 170 dB 수준의 충격 소음원에서 주파수별 귀마개의 차음성능을 확인하고, 주파수 특성과 패턴 형상을 분석하는데 있다. 충격 소음에서의 주파수별 귀마개 차음성능을 분석하기 위하여 충격 소음원 분석을 위한 설비를 구축하였다. 차음 성능을 확인하기 위해서 Ear시뮬레이터를 제작하여 차음성능을 검증하였다. 기존의 연구들은 충격 소음원이라 할지라도 대부분 140 dB 수준의 고충격 소음원이였으나, 본 연구는 그보다 더 높은 수준의 충격 소음원이라는 특징을 가지고 있다. 연구결과, 주파수별 충격소음의 차음효과는 평균 30 dB 정도임을 확인할 수 있었으나, 한정된 샘플링으로 인해 통계학적 추 검정 과정을 수행하지 못한 한계점이 있다.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.3
• /
• pp.82-89
• /
• 1995

A sound field simulator is constructed to obtain the sound field paramaters such as the magnitudes and directions of early reflections with moderate efforts. The proposed simulator is based on the hybrid ray tracing method that traces rays reached the listener position and convert them to image sound sources. By this approach, we can obtain the directional impulse response relatively easily with minimum casts. Simulation experiment results of several performace places are reported to how the versatility of the proposed simulator system.