• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.1
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• pp.18-25
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• 2018

In this paper, we present a low-power implementation of the multi-channel hearing aid system using a general-purpose DSP chip. The system includes an acoustic amplification algorithm based on Wide Dynamic Range Compression (WDRC), an adaptive howling canceller, and a single-channel noise reduction algorithm. To achieve a low-power implementation, each algorithm is re-constructed in forms of integer program, and the integer program is converted to the assembly program using BelaSigna(R) 250 instructions. Through experiments using the implementation system, the performance of each processing algorithm was confirmed in real-time. Also, the clock of the implementation system was measured, and it was confirmed that the entire signal processing blocks can be performed in real time at about 7.02MHz system clock.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.298-304
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• 2016

In this paper, a wavelet packet transform method is proposed for improving the altitude control performance of quadrotor UAV using an ultrasonic rangefinder. A ground tests are conducted using an ultrasonic rangefinder that is much used for vertical takeoff and landing. An ultrasonic rangefinder suffers from signal's spike due to specular reflectance and acoustic noise. The occurred spikes in short time span need to be analyzed at both sides time and frequency domain. The analyzed spikes of the ultrasonic rangefinder using a wavelet packet transform. Compared with the discrete wavelet transform, the wavelet packet decomposition can obtain more abundant time-frequency localization information, so it is more suitable for analyzing and processing ultrasonic signals spike. Experimental results show that it can effectively remove the spikes of the ultrasonic rangefinder.

• Journal of KIISE
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• v.41 no.10
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• pp.745-761
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• 2014

To address the problems of existing traffic information acquisition systems such as high cost and low scalability, wireless sensor networks (WSN)-based traffic information acquisition systems have been studied. WSN-based systems have many benefits including high scalability and low maintenance cost. Recently, various sensors are studied for traffic surveillance based on WSN, such as magnetic, acoustic, and accelerometer sensors. However, ultrasonic sensor based systems have not been studied. There are many issues for WSN-based systems, such as battery driven operation and low computing power. Thus, power saving methods and specific algorithms with low complexity are necessary. In this paper, we introduce optimal methodologies for power saving of ultrasonic sensors based on the modeling and analysis in detail. Moreover, a new vehicle detection algorithm for low complexity using ultrasonic data is presented. The proposed methodologies are implemented in a tiny microprocessor. The evaluation results show that our algorithm has high detection accuracy.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.522-528
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• 2011

Artificial basilar membranes made of PVDF(polyvinylidene fluoride) are manufactured using microfabrication processes. The mechanical behavior of PVDF artificial basilar membrane was measured to evaluate its performance as a mechanical frequency analyzer using scanning LDV(laser Doppler vibrometer). The experimental setup consists of the microfabricated artificial basilar membrane, a loud speaker connected to an amplifier for generating acoustic pressure of specific spectral pattern, and a scanning LDV with controlling unit for measuring the displacement of the membrane on the incoming acoustic stimulation. The microfabricated artificial basilar membrane was attached tightly upon a package containing a chamber which can be filled with silicone oil before placed on the experimental setup stage. The experiment results showed that the microfabricated artificial basilar membrane has a property as a mechanical frequency analyzer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.132-136
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• 2007

In case of indoor gymnastics training floor, in view of its characteristics, since it is simultaneously required the related smooth communication between the coach and the player, also the acoustic performance regarding to the Clearness of Music, besides the sport activity, the consideration about the acoustic character has entered the stage as an indispensable element. On such viewpoint, on the object of the recently built dome-typed gymnastics training floor, after making the optimized acoustic design with the remodeling through acoustic simulation, by means of measurement and valuation on human's psychological(sensual) degree utilizing Auralization that enables to experience the virtual sound field at the stage of design, this thesis has attempted to survey of the acoustic satisfaction degree and its reaction about the gymnastics training floor. As the result of investigation about the research on the space of object, it could be known that the valuation regarding to the acoustic performance of 'After-Improvement' was distinctly more refined than that of 'Before-Improvement'. It is now considering that such result of the study can be utilized as the useful data which enables to improve the retrenchment effect of the construction cost as well as the acoustic capability, by means of the prediction control on the acoustic problem from the stage of design, for the occasion when the similar indoor sport gymnasium is planning to build for the near future.

• The Journal of the Acoustical Society of Korea
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• v.13 no.2E
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• pp.58-67
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• 1994

Hidden Markov Model (HMM)-based algorithms have been used successfully in many speech recognition systems, especially large vocabulary systems. Although general purpose processors can be employed for the system, they inevitably suffer from the computational complexity and enormous data. Therefore, it is essential for real-time speech recognition to develop specialized hardware to accelerate the recognition steps. This paper concerns with a real-time implementation of an isolated word recognition system based on HMM. The speech recognition system consists of a host computer (PC), a DSP board, and a prototype Viterbi scoring board. The DSP board extracts feature vectors of speech signal. The Viterbi scoring board has been implemented using three field-programmable gate array chips. It employs a hardware-efficient Viterbi scoring architecture and performs the Viterbi algorithm for HMM-based speech recognition. At the clock rate of 10 MHz, the system can update about 100,000 states within a single frame of 10ms.

• Journal of IKEEE
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• v.24 no.2
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• pp.604-609
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• 2020

We investigated the influence of rapid thermal annealing on aluminum nitride (AlN) thin film Schottky barrier diodes (SBDs) manufactured structures deposited on a 4H-silicon carbide (SiC) wafer using radio frequency sputtering. The Ni/AlN/4H-SiC devices annealed at 400℃ exhibited Schottky barrier diode (SBDs) properties with an on/off current ratio that was approximately 10 times higher than that of the as-deposited device structures and the devices annealed at 600℃ as measured at room temperature. Auger electron spectroscopy (AES) measurements revealed that atomic oxygen concentrations in the annealed AlN devices at 400℃, is ascribed to the improvement in on/off ratio and the reduction of on-resistance. Additionally, we investigated the electrical characteristics of the AlN/SiC SBD structures depending on the frequency variation of sound waves.

• Geophysics and Geophysical Exploration
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• v.20 no.3
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• pp.129-136
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• 2017

3D seismic data processing methods such as full waveform inversion or reverse-time migration require 3D wave propagation modeling and heavy calculations. We compared efficiency and accuracy of a Xeon Phi coprocessor to those of a high-end server CPU using 3D frequency-domain wave propagation modeling. We adopted the OpenMP parallel programming to the time-domain finite difference algorithm by considering the characteristics of the Xeon Phi coprocessors. We applied the Fourier transform using a running-integration to obtain the frequency-domain wavefield. A numerical test on frequency-domain wavefield modeling was performed using the 3D SEG/EAGE salt velocity model. Consequently, we could obtain an accurate frequency-domain wavefield and attain a 1.44x speedup using the Xeon Phi coprocessor compared to the CPU.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.15 no.1
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• pp.37-42
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• 2004

Electrolarynx(EL), battery operated vibrators which are held against the neck by on-off button, has been widely used as a verbal communication method among post-laryngectomized patients. EL speech can produce easily without need of any additional surgery or special training and be used with any other methods. This institute developed a neck-typed EL named "Blueton" in commperation with EL Company Linkus, which consists of 3 parts : Vibrator part, Control part, Battery part. In this study we evaluated the acoustic characteristics of the produced voices by Blueton compared with Servox-inton using MDVP. Three EL users (2 full time users, 1 part time user) were participated. The results revelaed that NHR higher in Servox than Blueton and intensity is higher in Blueton than Servox. The spectra for vowels produced by EL speakers are mixed signals combined with talkers' vocal output and electrolarynx noise. The spectra pattern is similar with two ELs. High, SPI index and vowel spectra from MDVP demonstrated characteristics of both electrolarynxes related to noise signal. This finding suggests that Blueton helps to provide one of useful rehabilitation options in the post laryngectomy patients.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.327-327
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• 2010

자동차에서 실내음질은 구매결정 요소들 중의 하나로 그 중요성이 점차 증가하고 있다. 따라서 다양한 운전조건에서 운전자가 기대하는 실내음질의 기대 수준을 충족시켜야 한다. 소비자는 운전경험과 습관에 따라 기대하는 음질에 차이가 있고 소리에 대한 표현방식도 모호하기 때문에 이러한 주관적 특성을 하나의 통일된 표현으로 정의 하기가 어렵다. 그러나 지난 이십여 년 동안의 음질개발과 차량 실내소음 주관평가의 통계처리로 통일된 표현을 할 수 있었다. 나아가 심리음향학 및 신호처리기술의 발달과 꾸준한 음질연구결과로 소리특성을 객관적으로 나타내는 소리의 시각화가 가능하였으며, 운전자가 인식하는 주관평가와의 상관관계를 높여 차량의 대표적인 음질인자로 정량화하여 음질목표를 설정할 수 있었다. 실내소음의 구성은 엔진 투과음, 흡배기 소음, 바람 소음, 도로 기인 소음 등으로 다양하므로 소음원에 따라 음의 균형을 맞추어 조화로운 음질개발을 하는 것이 중요했다. 또한 차량 판매되는 지역에 따라 선호음이 상이하여 지역별 실내음질의 차별화가 필요했다. 궁극적으로는 운전자의 감성품질을 만족할 수 있도록 음을 제어하여 브랜드 사운드를 개발하고 있다. 이러한 실내음질을 달성하기 위한 방법으로 소음원과 전달경로에 대해 기여도를 분석하고, 경로를 구성하는 시스템 별로 세분화하여 시스템 목표를 설정하였다. 시스템 개발에 중요한 인자로 차량의 동강성 및 흡차음 성능을 들 수 있다. 특히 디젤차량의 비중이 큰 유럽업체의 차량의 동강성 및 흡차음 개발 능력은 높게 평가되고 있다. 이에 유럽의 부품전문회사가 가지고 있는 해석과 시험적인 개발 방법을 통하여 전달계 특성을 만족하기 위한 시스템의 동강성 및 흡차음 특성을 개발하고 있다. 차량음질 튜닝의 중요한 기법 중 하나로 흡배기 개발을 추진하고 있다. 친환경자동차인 하이브리드차량, 전기차량 및 연료전지차량의 경우 전기구동부품에서 발생하는 각종 이음 발생을 최소화 했다. 보행자를 보호하고 운전의 즐거움을 향상하기 위한 가상사운드 개발을 진행하고 있다. 회사 수익성 향상을 위한 원가절감 및 구조 경량화에 따른 음질악화와 연비 향상 및 배기가스 규제 강화로 고성능 고출력 엔진탑재에 따른 음질악화 요인을 극복해야 했다. 운전자의 청감은 차량의 운전성에 따라서도 크게 영향을 받게 되므로 엔진제어와 변속기제어를 통해 음질과 운전성이 조화를 이룰 수 있도록 개발하고 있다. 향후, 소음원에 따른 시스템 최적화 개발, 운전성과 음질 연계 개발과 친환경차량의 가상사운드 개발 등이 자동차 음질 개발의 중요한 이슈로 생각한다.