• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.48 no.5
• /
• pp.109-114
• /
• 2011

In this paper, we apply a context awareness based on Gaussian mixture model (GMM) to a sound reinforcement for hearing impaired. In our approach, the harmful sound amplified through the sound reinforcement algorithm according to context awareness based on GMM which is constructed as Mel-frequency cepstral coefficients (MFCC) feature vector from sound data. According to the experimental results, the proposed approach is found to be effective in the various acoustic environments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.04a
• /
• pp.202-207
• /
• 1995

BAZOOKA SPEAKER에 대한 음향특성연구와 중저음 특성강화를 위한 설계인자 변경해석을 위하여 유한요소법과 경계요소법을 사용한 수치해석을 수행하였고, 그 해석결과의 검증과 흡음물성치 산출을 위하여 음향측정실험, 구조물의 동특성실험등을 실시하였다. 연구결과, 내부공간의 음향모드특성, 외부음장에서의 주파수응답특성, 방사패턴, 그리고 음압의 공간 분포특성과 구조물의 동특성을 명확히 규명하였고, 각 음향설계인자 변경에 따른 음향특성을 예측하여 중저음특성강화를 위한 방안을 수립하였다.

• Broadcasting and Media Magazine
• /
• v.2 no.3
• /
• pp.23-31
• /
• 1997

컴퓨터 음향발생에 관한 연구는 컴퓨터 음악, 인간-컴퓨터 상호작용, 데이터 청각화등의 분야에서 오랫동안 진행되어 왔지만, 최근 들어 컴퓨터 애니메이션이나 가상세계등에서 시각적 효과와 함께 보다 입체감 있고 현실감 있는 가상환경을 제공하기 위해 더욱더 중요한 문제로 떠오르고 있다. 지금까지 음향발생을 위해 음향의 모델링이나 합성등 음향 자체에 대한 요소 기술들에 관해서는 많은 연구가 진행되었으나 컴퓨터 애니메이션, 가상세계등과 같이 영상내 동작 내지 사건과 음향이 서로 밀접하게 연관된 분야에서 필수적인 음향을 영상내 동작과 통합 처리할 수 있는 기술에 대한 연구는 초보적인 단계에 머무르고 있다. 최근 들어, 음향의 입체감과 임장감을 강화하기 위하여 3차원 음향이라는 개념이 도입되고 있고 이의 구현에 대한 연구가 활발하게 진행되고 있다. 여기서는 컴퓨터 애니메이션이나 가상현실등에서 영상내 물체의 움직임이나 사건 그와 동기된 음향의 자동생성 및 이의 3차원 음향효과 발생 기술 원리를 사이버음향(CyberSound)이라는 개념으로 묶어서 소개하면서, 이의 전망을 기술하고자 한다.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.6
• /
• pp.353-359
• /
• 2011

This paper proposes a vocal enhancement technique for improving the performance of vocal pitch detection in polyphonic music signal. The proposed vocal enhancement technique predicts an accompaniment signal from the input signal and generates an accompaniment replica signal according to the vocal power. Then, it removes the accompaniment replica signal from the input signal, resulting in a vocal-enhanced signal. The performance of the proposed method was measured by applying the same vocal pitch extraction method to the original and the vocal-enhanced signal, and the vocal pitch detection accuracy was increased by 7.1 % point in average.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.5
• /
• pp.381-389
• /
• 2000

Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.

• Journal of the Institute of Convergence Signal Processing
• /
• v.11 no.3
• /
• pp.203-208
• /
• 2010

In this paper, we convert underwater acoustic signal made by sonar system into digital image. We propose the algorithm that detects target candidate and emphasizes information of target introducing image processing technique for the digital image. The process detecting underwater target estimates background noise in underwater acoustic signal changing irregularly, recomposes it. and eliminates background from original image. Therefore, it generates initial target group. Also, it generates weighted map through proceeding doppler information, ensures information for target candidate through filtering using weighted map for image eliminated background noise, and decides the target candidate area in the single frame. In this paper, we verified that proposed algorithm almost had eliminated the noise generated irregularly in underwater acoustic signal made by simulation, targets had been displayed more surely in the image of underwater acoustic signal through filtering and process of target detection.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.17 no.4
• /
• pp.42-47
• /
• 2009

Recently, the wide range of the composite materials is used for the making airplanes, trains and automobiles body for the lightweight. Despite having complex structures, composite materials usually have well defined mechanical characteristics. However, composite materials are difficult to understand the fracture mechanism clearly by simple mechanical test. Nondestructive evaluation (NDE) combined with mechanical testing can play a more important role and especially Acoustic Emission Testing (AET) would become known to be a useful tool to assess damage and fracture behavior of composites. In this study The experiment was performed to acquire the acoustic emission signal during tensile test using unidirectional CFRP specimen and the data was analyzed the acoustic emission parameters with the waveform.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.5
• /
• pp.430-435
• /
• 2013

This study is investigation of the characteristics for acoustic emission signal generated by destruction on glass fiber bundles and specimen that was machined composite materials surrounding the outside of GFRP cylinder. The Amplitude of acoustic emission signal gets bigger as the cutting angle of knife increases. Accordingly, the number of hits in destruction of composite materials specimen have more in longitudinal direction (longitudinal direction to the glass fiber) than in hoop direction (horizontal direction to the glass fiber) while the amplitude of signals were bigger in hoop direction than longitudinal direction. It was found out that the amplitude of the glass fiber breakage is more than 40 dB and that the amplitude of signal for matrix crack was less than 40 dB because matrix crack signal was not observed when threshold value is 40 dB and matrix crack signal suddenly appered when threshold value is 32 dB. The slope of the amplitude is related to the acoustic emission source and the slope of the amplitude of the horizontal and vertical directions are 0.16 and 0.08. In particular, The slope of the amplitude of longitudinal direction breakage appear similar to the glass fiber breakage and therefore Acoustic emission source of longitudinal direction breakage is estimated the glass fiber breakage.

• Composites Research
• /
• v.17 no.4
• /
• pp.61-67
• /
• 2004

Nondestructive damage sensitivity on single-basalt fiber/epoxy composites was evaluated by micromechanical technique and acoustic emission (AE). Piezoelectric lead-zirconate-titanate (PZT), polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer were used as AE sensor, respectively. In single-fiber composite, the damage sensing with different sensor types were compared to each other. Piezoelectric PVDF polymer sensor was embedded in and attached on the composite, whereas PZT sensor was only attached on the surface of specimen. In case of embedded polymer sensors, responding sensitivity was higher than that of the attached case. It can be due to full constraint inside specimen to transfer elastic wave coming from micro-deformation. For both the attached and the embedded cases, the sensitivity of P(VDF-TrFE) sensor was almost same as that of conventional PVDF sensor.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.4
• /
• pp.301-307
• /
• 2013

SONAR detection performance is one of the key survivability factors in underwater weapon systems. In order to catch the acoustic ability of SONAR, multilayer SONAR structures are analyzed using the elastic theory. The applied results for the simple models are compared with those from commercial program, ANSYS, and the reliable results are obtained. The analysis of sound pressure level (SPL) and echo reduction (ER) by the thickness change of multilayer SONAR structures are performed using the verified elastic theory. As the thickness of anechoic layer is increased, SPL is distributed evenly and ER is increased slightly with the frequency. In decoupling layers and steel layers, SPL are hardly changed and ER is slightly decreased with the thickness increase of those layers. SPL and ER are not affected by the thickness change of the carbon reinforced plastic (CRP) layer. Therefore, to improve the acoustic ability of multilayer SONAR structures, the thickness increase of the anechoic layer and minimization of the decoupling layer, steel layer and CRP layer are desirable.