• 대한인간공학회지
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• 제32권4호
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• pp.363-370
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• 2013

Objective: This study investigates the influences of vibrations on hedonic satisfaction based on four kinds of perceptions (perceived ease of use, perceived usefulness, perceived enjoyment, cognitive concentration) when mobile gaming. Background: As mobile gaming is becoming more and more popular for smartphone users, they might want to have more hedonic satisfaction instead of focusing on traditional usability criteria such as efficiency, effectiveness, and satisfaction. Method: We conducted a human-factors experiment with 35 male subjects to evaluate hedonic satisfaction in the mobile game configured by 7 vibration types having different levels of intensity and length. Results: The results revealed that the use of vibration significantly increases the perceived ease of use, perceived usefulness, and cognitive concentration. In addition, the intensity of vibration makes differences of perceived usefulness and cognitive concentration. Conclusion: Vibration can be effectively used to improve hedonic satisfaction of smartphone users in mobile gaming when they are not allowed to turn the sound effects on. Application: This study helps game designers effectively provide vibration feedback of mobile games for smartphone users.

• 대한의용생체공학회:의공학회지
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• 제36권5호
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• pp.143-149
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• 2015

In this paper, we proposed a novel method for automatic detection for snoring and heart beat using a single piezoelectric sensor. For this study multi-rate signal processing technique was applied to detect snoring and heart beat from the single source signal. The sound event duration and intensity features were used to snore detection and heart beat was found by autocorrelation. The performance of the proposed method was evaluated on clinical database, which is the nocturnal piezoelectric snoring data of 30 patients that suffered obstructive sleep apnea. The method achieved sensitivity of 88.6%, specificity of 96.1% with accuracy of 95.6% for snoring and sensitivity of 94.1% and positive predictive value of 87.6% for heart beat, respectively. These results suggest that the proposed method can be a useful tool in sleep monitoring and sleep disordered breathing diagnosis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
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• pp.10-14
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• 1989

This paper shows an experimental study of home appliance motor noise, also represents some relations between skew-types and skew-angles. Frequency analysis was made for stator and rotor harmonic fluxes. making use of searching coils. Besides electrical analysis, mechanical noise trans mission analysis are studied to lee how they affected on the noise of the motor. Finally, we proved the noise sources of the motor using sound intensity method.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.61-65
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• 2001

A new flaw detection technique using by SH angle beam method has been discussed. The SH-wave is horizontally polarized shear wave and the surface SH wave has a characteristic of traveling along near surface layer. The surface SH wave technique is valuable for the detection of fatigue cracks at fillet weld heels which cannot be detected by other ultrasonic technique such as angle beam technique and The dispersion curves of it has simple characterization. In this work, using these beneficial chraterization, quality evaluation of spot weld with ultrasonic sound intensity of SH-wave passing through nugget area of spot weld are verified experimentally.

• 소음진동
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• 제8권1호
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• pp.187-194
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• 1998

In order to predict the train noise propagation from a level railroad, this paper presents the model of train noise source and the prediction model based on the results by using the sound intensity method. The prediction model gives the effects of geometric attenuation, ground attenuation, and barrier attenuation of noise. There are several principal assumption in developing model: (a) the train noise is primarily rolling noise; (b) the rail head and wheels are in good condition; (c) the height of source is 10cm above track; (d) the directivity pattern of train noise sources is a dipole source. Calculated results based on this model are compared with available field data and good agreement has been obtained.

• 한국소음진동공학회논문집
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• 제17권10호
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• pp.950-957
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• 2007

This paper considers acoustic characteristics of silencer within a dry vacuum pump. The main objective is to reduce noise in dry vacuum pump using the new designed silencer. First, SPL and sound intensity are measured for noise source identification and the new model silencer is designed corresponding to noise characteristics. 4-pole parameters are used to predict the transmission loss which is one of the interest characteristics of the new silencer. The calculated transmission loss is then used to change main effective factor and optimal value is selected by using design of experiment. By conducting an experiment, it is proved that the new designed silencer has reduced noise level by 6 dB(A) more than the original one.

• 한국항공우주학회지
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• 제30권1호
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• pp.28-35
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• 2002

공동흐름에서 직각 계단은 커다란 소음의 원인이 되어 많은 사람들의 와류와 직각계단의 상호 작용 시에 발생되는 소음의 저감 방안을 연구하여 왔다. 본 연구에서는 2차원 저아음속 와류 흐름이 전향계단을 지날 때 발생되는 유동 소음을 전향계단의 형상 변화를 통한, 즉, 계단의 모따기 양과 각도를 바꾸어 가면서 수치적으로 계산하였다. 내부 유동장을 구하기 위해서 비압축성 비점성 이산와류 모델을 가정하였으며, 유동정보로부터 원거리로의 음향장 계산은 MAE 이론을 적용하여 구하였다. 음원에서의 음압과 음압강도를 모따기 높이 및 모따기 각도와 최기 와류의 높이를 변화시켜가면서 다양하게 수치적인 결과를 얻어내었다. 본 연구를 통해서 계단에 접근하는 와류에 의한 원거리 음압은 모따기 양이 계단 높이의 30%에서 모따기 각도가 $15^{\circ}C$에서 $30^{\circ}C$°사이일 때 가장 소음이 적게 발생되는 결과를 얻어내었다.

• 한국통신학회논문지
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• 제25권9B호
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• pp.1551-1562
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• 2000

국내에서 개발된 광섬유 격자{FBG)를 사용하여 국내 최초로 3종의 FBG 음향 트랜스듀서를 설계 및 제작하였다. 제작된 FBG 트랜스듀서들에 대하여 수중에서 각각 주파수응답특성 설험을 하고, 그 특성을 분석하였다. 주파수 응답특성실험 결과 C형태는 최대 18 kHz대까지 수중음파 검출이 기능하였다. 또한, 수중에서 넓은 영역에 대한 다중점 신호검출을 구현하기 위하여, 파장분활 방법과 Passive band-pass filter system을 이용하여 어레이 시스템을 구축하고 2개의 B형태 FBG 트랜스듀서에서 주파수 1.3 kHz대까지 다중점 수중 음파 신호검출을 성공하였다. 아울러, 음원의 방향과 각도에 따라 검출 신호의 세기가 변화되므로 음원의 물체에 대한 방향성 검출이 가능함으로서, 향후 FBG 하이드로폰의 실용화 연구에 새로운 기틀을 마련하였다.

• Imaging Science in Dentistry
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• 제51권2호
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• pp.107-115
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• 2021

Purpose: This study aimed to demonstrate the presence of dental caries through a photoacoustic imaging system with visible and near-infrared wavelengths, highlighting the differences between the 2 spectral regions. The depth at which carious tissue could be detected was also verified. Materials and Methods: Fifteen permanent molars were selected and classified as being sound or having incipient or advanced caries by visual inspection, radiography, and optical coherence tomography analysis prior to photoacoustic scanning. A photoacoustic imaging system operating with a nanosecond pulsed laser as the light excitation source at either 532 nm or 1064 nm and an acoustic transducer at 5 MHz was developed, characterized, and used. En-face and lateral(depth) photoacoustic signals were detected. Results: The results confirmed the potential of the photoacoustic method to detect caries. At both wavelengths, photoacoustic imaging effectively detected incipient and advanced caries. The reconstructed photoacoustic images confirmed that a higher intensity of the photoacoustic signal could be observed in regions with lesions, while sound surfaces showed much less photoacoustic signal. Photoacoustic signals at depths up to 4 mm at both 532 nm and 1064 nm were measured. Conclusion: The results presented here are promising and corroborate that photoacoustic imaging can be applied as a diagnostic tool in caries research. New studies should focus on developing a clinical model of photoacoustic imaging applications in dentistry, including soft tissues. The use of inexpensive light-emitting diodes together with a miniaturized detector will make photoacoustic imaging systems more flexible, user-friendly, and technologically viable.

• 대한후두음성언어의학회지
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• 제16권1호
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• pp.10-14
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• 2005

Background and Objectives : Vowels are characterized on the basis of formant patterns. The first formant(F1) is determined by high-low placement of the tongue, and the second formant (F2) by front-back placement of the tongue. The fundamental frequency(F0) of a soprano often exceed the normal frequency of the first formant. And the vocal intensity is boosted when F0 is high and a harmonic coincides with a formant. This is called a formant tuning. Experienced singers thus learned how to tune their formants over a resonable range by lowering the tongue to maximize their vocal intensity. So, the current study aimed to identify the formant tuning in one experienced soprano by comparing the first formants of vowel [i] in three different voice production : speech, ascending scale, and vocalize. Materials and Method : All voices recordings of vowel [i] in speech, ascending scale (from F4 note to A4 note), and vocalize(:Ridente la calam") were made with digital audio tape-corder in a sound treated room. And the captured data were analyzed by the long term average(LTA) power spectrum using the FFT algorithm of the Computerized Speech Lab(CSL, Kay elementrics, Model, 4300B). Results : Although the first formant of vowel [i] in speech was 238Hz, those of ascending scale [i] were 377Hz, 405Hz, 453Hz respectively in F4(349z), G4(392Hz), A4(440Hz) note, and 722Hz, 820Hz, 918Hz respectively in F5 (698Hz), G5(784Hz), A5(880Hz) note. In vocalize, first formants of [i] were 380Hz, 398Hz, 453Hz respectively in F4, G4, A4 note, and 720Hz, 821Hz, 890Hz respectively in F5, G5, A5 note. Conclusion : These results showed that the first formant of ascending scale and vocalize sustained higher frequency than fundamental frequency in high pitch. This finding implicates that the formant tuning of vowel [i] in ascending scale was also noted in vocalize.