• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.121-124
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• 1993

This paper is a study on the word recognition using neural network. A limited vocabulary, speaker independent, isolated word recognition system has been built. This system recognizes isolated word without performing segmentation, phoneme identification, or dynamic time wrapping. It needs a static pattern approach to recognize a spatio-temporal pattern. The preprocessing only includes preceding and tailing silence removal, and word length determination. A LPC analysis is performed on each of 24 equally spaced frames. The PARCOR coefficients plus 3 other features from each frame is extracted. In order to simplify a structure of neural network, we composed binary code form to decrease output nodes.

• The Journal of the Acoustical Society of Korea
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• v.4 no.2
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• pp.3-12
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• 1985

The surface intensity method is a relatively new tool which can identify the noise source or path and measure the radiation power. One microphone and one accelerometer are used in this new technique. In this study, this new technique has been used to measure the field transmission loss trough doors. The results of the experiment indicate that the surface intensity method produces reliable data and can be applied to the transmission loss measurement.

• The Journal of the Acoustical Society of Korea
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• v.4 no.2
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• pp.3.1-3.1
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• 1985

The surface intensity method is a relatively new tool which can identify the noise source or path and measure the radiation power. One microphone and one accelerometer are used in this new technique. In this study, this new technique has been used to measure the field transmission loss trough doors. The results of the experiment indicate that the surface intensity method produces reliable data and can be applied to the transmission loss measurement.

• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.66-69
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• 1984

This paper is a study on the Endpoint Detection for Korean Speech Recognition. In speech signal process, analysis parameter was classification from Zero Crossing Rate(Z.C.R), Log Energy(L.E), Energy in the predictive error(Ep) and fundamental Korean Speech digits, /영/-/구/ are selected as date for the Recognition of Speech. The main goal of this paper is to develop techniques and system for Speech input ot machine. In order to detect the Endpoint, this paper makes choice of Log Energy(L.E) from various parameters analysis, and the Log Energy is very effective parameter in classifying speech and nonspeech segments. The error rate of 1.43% result from the analysis.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.201-204
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• 1998

This paper study on blind adaptive interference suppression algorithm without training sequence to solve Near-Far problem due to multi access interference. And the performance of each algorithm in the presence of the multipath fading channels over DS-CDMA is evaluated. Simulation results showed that Modified LMS-CMA algorithm has a higher capacity than MOE in SIR/SNR.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.5-10
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• 1990

This study was examined for traffic noise by platoon dispersion in relation to traffic flow till platoon reach steady driving condition after starting from stopline. Platoon dispersion factor was calculated and evaluated by the following input data : traffic volume, travel time, pass time.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.153-156
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• 2000

최근의 야외경기장의 설계는 운동 경기 뿐만 아니라 각종이벤트 및 대형콘서트를 수용하는 다목적경기장으로 건설되어지고 있으며 지붕의 $50\%이상이 천장으로 덮히는 야외경기장의 건설이 증가하는 추세로 변화되고 있으며 이에 대한 음향장해 현상이 심각한 실정이나 이에 대한 건축음향적인 대책은 미미한 실정이다. 본 연구는 서울월드컵경기장을 중심으로 음향특성을 분석하고 음향시뮬레이션을 통하여 중요음향인자 (음압레벨, 잔향시간, 명료도)들을 분석하고 보완방법을 연구하는데 그 목적이 있다.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.9-16
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• 2001

This paper deals with the inverse reconstruction of sectional area in nonuniform ducts by using the acoustical measurement. There have been many theoretical and experimental studies on the duct area reconstruction. In this research, the method using the impulse response function and area reconstruction algorithm was employed because of its mathematical and experimental simplicity. Based on the study results on the drawback of conventional impulse excitation method, a new measurement method is proposed, that uses the random noise source and the discrete inverse Fourier transform. It is found that the reconstruction errors of the present method is smaller than the conventional method. A random error analysis is performed in order to investigate the causes of reconstruction error and to clarify the applicable data range for area reconstruction.

• The Journal of the Acoustical Society of Korea
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• v.24 no.3E
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• pp.90-98
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• 2005

Enhanced approach using computational and experimental method is proposed and performed to describe very well the behavior of loudspeaker than conventional method. Proposed procedure is composed of four parts. First, Thiele-Small parameters for test loudspeaker are identified by an electrical impedance method like as a delta mass method. Second part includes the processes to measure physical properties. Physical data like masses and thicknesses of loudspeaker's components are measured by an electrical precision scale and a digital vernier caliper. Third, the identified Thiele-Small parameters are proposed to be used as load boundary conditions for vibration analysis instead of electromagnetic circuit analysis to get a driving force upon bobbin part. Also, these parameters and physical data are used to modify physical properties required for computation to accommodate simulated sound pressure level with measured one for loudspeaker enclosure system. These data like as Young's modulus and thickness for a diaphragm are required for vibration analysis of loudspeaker but not measured accurately. Finally, it was investigated that simulated sound pressure level with full acoustic modeling including an acoustic port for test loudspeaker agreed with experimental result very well in the midrange frequency band(from 100 Hz to 2,000 Hz). In addition, several design parametric study is performed to grasp acoustical behaviors of loudspeaker system due to variations of diaphragm thicknesses and shapes of dust cap.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.93-99
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• 2006

Flexible couplers are widely used for exhaust transmitted vibration reduction in vehicles. This paper describes an investigation into the acoustical characteristics of exhaust flexible coupler by the simulation and testing. Computational acoustic simulation is carrying out to investigate resonance frequency and transmission loss of decoupler using the boundary element method and transfer matrix approach. To confirm the acoustical simulation results of exhaust decoupler, we compare with measured experimental results by the test of transmission loss measurement system. In the comparison with simulation results and tests results, there is correctly fit the resonance frequency and the trend of transmission loss. Also, we show that the acoustical structure of decoupler is analogous to the expended tube or side branch resonator. The characteristics of exhaust decoupler have a marked increase in the acoustic attenuation at the specified frequency bend. Therefore the decoupler is applied to develop the exhaust system not only for the vibration isolator but also for the noise attenuator.