• Korean Journal of Materials Research
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• v.20 no.12
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• pp.640-644
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• 2010

Information technology devices, such as cellular phones, MP3s and so on, due to restrictions of space, require thin and small micro-speakers to generate sound. The reduction of the size of micro-speakers has resulted in the decrease of sound quality, due to such factors as frequency range and sound pressure level. In this study, the acoustical properties of oval microspeakers has been studied as a function of pattern shape on the diaphragm. The other conditions of micro-speakers, except for the pattern, was not changed. When the pattern is present on the diaphragm and the shape of pattern was a whirlwind, the resonance frequency was reduced due to the decrease of tensile strength of diaphragm. The patterns presented in the semi-minor axis of diaphragm did not effect a change of resonance frequency. However, increasing the number of patterns in the semimajor axis of diaphragm became a reason for the decrease of resonance frequency on edge side. When the depth of pattern on edge side was increased, the resonance frequency was decreased due to reduction of geometrical stiffness. If the height of edge and dome were increased, the resonance frequency and geometrical stiffness rapidly increased. After reaching the maximum values, they began to decrease with the continuous increase of height.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.10 s.115
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• pp.997-1004
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• 2006

With the growth in electronics and the remarkable advance in wireless communication technology, mobile devices, such as mobile phones and PDAs are incessantly improved in their diverse functional performance. Lighter weight and smaller size has been gradually accomplished by recent circuit integration technology resulting in rapid growth in the number of mobile phone subscribers. Driven by customer demand, recent mobile devices are fully capable of realizing a variety of dazzling multimedia effects powered by electro-acoustic parts that have become one of the generic components. However, This paper also presents an oval micro-speaker, that is' expected to show an excellent performance within limited space of mobile phone, and its performance design has been suggested as well. Finally, a statistical approach to achieve high characteristic and performance is suggested by Taguchi method to identify a certain relationship between a mobile phone and a micro-speaker.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.327-327
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• 2007

This paper reports the simulation results of piezoelectric microspeakers due to structural changes(diaphragm materials, corrugation width and electrode shapes). When we compared the dependence of diaphragm material properties, the microspeaker with LTO(Low Temperature Oxide) diaphragm shows higher deflection than that of silicon nitride diaphragm, even though the resonant frequencies are almost same in both cases. In case of circular-electrode microspeaker, the deflection of diaphragm is about $16\;{\mu}m$ at 20 V, and it decreases as the corrugation width is decreased. However, the deflection of diaphragm with the square-electrode reveals almost twice times higher value at the same applied voltage than the circular one, and it increases as the corrugation depths are decreased from $30\;{\mu}m\;to\;10\;{\mu}m$. The first resonant frequency of microspeakers present about 1.8 kHz in circular-electrode and 1.2 kHz in square-electrode, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.37-38
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• 2007

This paper reports the characteristics of piezoelectric microspeakers that are audible in open air with high quality piezoelectric AlN thin film according to the materials properties. When we use a tensile-stressed silicon nitride diaphragm as a supporting layer, the Sound Pressure Level (SPL) is relatively small. However, the SPL of the fabricated microspeakers that have compressive-stressed composite diaphragm show higher output pressure than those of tensile-stressed diaphragm. It produces more than 60dB from 100Hz to 15kHz and the highest SPL is about 100dB at 9.3kHz with 20 Vpeak-to-peak sinusoidal input biases and at 10 mm distances from the fabricated microspeakers to the reference microphone.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.403-409
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• 2011

Micro speakers are used to reproduce sound in small electric and information and communications devices, such as cellular phones, PMPs, and MP3 players. The acoustical properties and sound quality, which are changed due to the decreased size of the speaker, are often adjusted varying the type and thickness of the diaphragm. The most widely used diaphragm material is thin polymer. It was previously reported by the author of this paper that the resonance frequency of a micro speaker is changed by the type and thickness of a polymer diaphragm. In this paper, the frequency response near the resonance frequency of a micro speaker was studied as functions of the type and thickness of the polymer diaphragm. While $R_{max}$ and $R_{DC}$ were affected by the type and thickness, an analysis of the electrical impedance curve revealed that $R_o(= R_{max}/R_{DC})$ and ${\Delta}f$ were not changed. Thus, $Q_{TS}$ which was function of $R_o$, ${\Delta}f$, and the resonance frequency, is only related to the resonance frequency. The increase of the resonance frequency led to a proportional rise of $Q_{TS}$. The change of the frequency response near the resonance frequency was not dependent on the type or thickness of the polymer diaphragm, but was affected by the resonance frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.493-496
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• 2005

With the growth in electronics and the remarkable advance in wireless communication technology, mobile devices, such as mobile phones and PDAs are incessantly improved in their diverse functional performance. Lighter weight and smaller size has been gradually accomplished by recent circuit integration technology resulting in rapid growth in the number of mobile phone subscribers. Driven by customer demand, recent mobile devices are fully capable of realizing a variety of dazzling multimedia effects powered by electro-acoustic parts that have become one of the generic components. However, this paper also presents an oval micro-speaker, that is expected to show an excellent performance within limited space of mobile phone, and its performance design has been suggested as well. Finally, a statistical approach to achieve high characteristic and performance is suggested by Taguchi method to identify a certain relationship between a mobile phone and a micro-speaker.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.5
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• pp.10-16
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• 1985

In this paper, a computer vision system, which catches printed music score image using CCTV camera and microcomputer, and then recognizes the image and performs tar music with speaker, is discussed. Integral projection method is adopted for feature detection and recognition of the music score image. The range of recognition is con(ined to staffs, perpen-dicular lines and musical notes including chord notes among the various kinds of elements of music score. The practical recognition algorithm considering noises, the preprocessing processes getting rid of noises are also showed, and simple hardware system playing chord is made, In the results, good recognition ratio and performance are obtained.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3219-3221
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• 2000

본 논문에서는 바이오피드백(Biofeedback) 항문 괄약근 조절 시스템(Anal Spincter Control System)을 제작 및 구현하였다. 제작 및 구현된 시스템은 특발성 만성 변비증 및 특발성 만성 또는 신경인성 만성 변실금증 환자의 항문 괄약근 훈련 및 치료에 유용하다. 본 논문의 주된 내용은 마이크로 볼트 단위의 미세한 신호인 항문 괄약근 근전도 신호를 왜곡없이 증폭하여 검출하기 위한 바이오피드백 항문 괄약근 근전도 증폭기 (Anal EMG Amplifier) 및 신호처리기(Signal Processor)로 구성되어 있으며 사용자가 항문 괄약근 근전도 신호를 확인할 수 있도록 LED display와 스피커 출력 기능을 구현하여 monitoring을 가능하게 했다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.531-537
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• 2006

A micromachined piezoelectric microspeaker was fabricated with a highly c-axis oriented ZnO thin film on a silicon-nitride film having compressive residual stress. When it was measured 3 mm away from the microspeaker in open field, the largest sound pressure level produced by the fabricated microspeaker was about 91 dB at around 2.9 kHz for the applied voltage of $6\;V_{peak-to-peak}$. The key technologies to these successful results were as follows: (1) the usage of a wrinkled diaphragm caused by the high compressive residual stress of silicon-nitride thin film, (2) the usage of the highly c-axis oriented ZnO thin film.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.128-133
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• 2002

We developed a electronic music glove (BMG) system that plays musical scores in real time processing. The EMG system interfaces with the signal coming from the controller to the sound card in the computer, The computer, according to the status of the fingers and foot switches, generates the sound signals and sends them to the speaker systems through the application C++ program and MIDI message. The EMG systems control the velocity and duration of sound and several musical performance expressions such as chorus, reverberation, rhythm, and volume. Finally, we implemented the digital drum set using: the EMG system as example.