• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.183-189
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• 2006

In mobile phones of multimedia era, microspeakers of high qualify sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.497-502
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• 2005

In mobile phones of multimedia era, microspeakers of high quality sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical, acoustical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.347-351
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• 1997

A micromachined piezoelectic cantilever transducer,which works both as a microphone and as a microspeaker,has been fabricated and tested. The 2000*2000*3.mu.m .sap2. cantilever has oxide(ZnO)piezoelectric thin film on a supporting layer of low-pressure chemical-vapor-deposited(LPCVD)low-stress siliconnitride. A highlight of the fabrication process which may also be relevant for other micromachined stuctures is the technique for producing a flat,multilayer cantilever. The measured microphone sensitivity is fairly constant at 2 mV/.mu.bar in the low frequency range and rise to 20 mV/.mu.bar at the lowest resonant frequency of 890 Hz. The 2 mV/.mu.bar sensitivity is the highest report to data for a microphone with a micromachined diaphragm. When measured into a 2 cm/sap3 coupler with 4V (zero-park)drive,the microspeaker output sound pressure level(SPL) is 75 dB at 890 Hz. It increases to approximately 100dB SPL at 4.8kHz with 6V(zero-park)drive. The measured microphone frequency response agrees well with the results of an ABAQUS simulation.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.509-510
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• 2021

본 논문에서는 라즈베리파이, 마이크, 스피커, 버튼센서, 진동센서, TTS(Text-To-Speech) api를 활용하여 유아용 언어 학습용 디바이스를 개발한다. 학습시키고 싶은 단어가 쓰여져 있는 상자를 유아가 건드리면 그 단어의 소리가 나는 것을 가정하였다. 사용자가 버튼을 통해 직접 단어를 녹음을 할 수 있으며 웹페이지를 통해 텍스트(영어)를 입력하면 text-to-speech api를 통해 텍스트(영어)에 맞는 음성파일을 제공받을 수 있다. 저장된 음성파일은 진동센서를 통해 진동이 감지되면 스피커를 통해서 출력이 되는 시스템으로 구성하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.45-46
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• 2005

The piezoelectric ZnO thin films were deposited onto Al/Si substrate in order to figure out the crystalline and the residual stress of deposited films. As the $Ar/O_2$ gas ratio is increased, c-axis orientation of deposited films is significantly enhanced and also the residual stresses of ZnO films are all compressive. They are decreased from -1.2 GPa to -950 MPa as the $Ar/O_2$ gas ratio is increased. A diaphragm-based piezoelectric microspeaker fabricated on ONO films shows about 14 mPa output pressure at 1 kHz with $8V_{peak-to-peak}$.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.27-33
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• 2010

This paper focuses on the design of microspeakers with minimum flux leakage, for use in radiotelegraphy. The response surface methodology (RSM) is applied as the optimization technique for obtaining a large magnetic force and a small flux leakage on diaphragm. The object functions of this optimization are the magnetic force and the flux leakage along three factors; pole piece thickness, magnet grade and yoke thickness, which are determined by the design of the experiment. The magnetic force and the flux leakage are calculated for each condition and optimized by results evaluated with RSM. For a pole piece thickness of 0.9 mm, a magnet grade of N42H and a yoke thickness of 0.75 mm, the magnetic force is satisfied as initial model and flux leakage is decreased to 11.8% than initial model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.2
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• pp.327-336
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• 2012

In this paper, we propose user authentication methods using a microphone and a speaker in smart phones. The proposed methods guarantee that the user is located close to the target device by transmitting the challenge via an audio channel. We propose two authentication methods; user authentication for a PC or a website using a smart phone as a hardware token, and user authentication to log on to a smart phone using a PC as a token. Because our methods use typical peripheral devices such as a microphone and a speaker, they do not require any special-purpose hardware equipment. In addition, the elderly and the handicapped can easily use our methods because the methods are activated by simple operations.