• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.7 no.1
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• pp.56-60
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• 1996

The vocal efficiency(VE) can be calculated as the ratio of acoustic power to aerodynamic power. It relates to the vocal intensity, air Sow rate and subglottic pressure. In this study, we treated 20 cases of vocal polyps and 10 cases of vocal nodules by way of laryngo-microsurgery or laser laryngo-microsurgery. The VE was measured preoperatively and postoperatively in all cases. The results showed that there was a significant improvement of VE postoperatively than that of preoperative measurement(p＜0.01) in vocal Polyp group. However, there was no significant difference(p＞0.05) in vocal nodule group. Through comparing the results, we obtained the conclusion : The laryngo-microsurgery is the reliable method of management for the vocal polyps, but f3r the vocal nodules, the laryngo-microsurgery should be selected after other more conservative approaches fail to produce the desired results.

• Journal of Biomedical Engineering Research
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• v.7 no.1
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• pp.21-34
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• 1986

In this paper, we described the ECG telemetry system via the Public Telephone Line. The system consist of a signal acquisition and measurement section, a signal processing section, and a signal transmission section. It used 8 bits microprocessor. The transmission section is composed of 3 ch. analog modulators and 1 ct. digital modem. Especially, using the digital modem, signal is transmitted with about 50n data reduction ratio by the TP (Turning Point) algorithm. The acoustic coupler or inductive coil for linking the public telephone line are used. The speed of the digital modem is 300 baud rate. The MCBS (Multi Channel Biotelemetry System) is tested and evaluated through the experiment.

• The Journal of the Acoustical Society of Korea
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• v.5 no.2
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• pp.39-47
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• 1986

흡음 계수는 흡음재의 흡음 특성을 제시해 주는 기본적 물리량이다. 본 연구에서는 일반적으로 흡음재로 사용되는 흡음재의 흡음 특성을 알기 위해 두께 18mm, 직경 105mm인 10종의 흡음재를 택하 여 흡음재의 흡음 계수를 구하였다. 이를 위해 impedance tube를 제작하여 관내에 흡음재를 넣은 후 관 내에 만들어진 정상파의 최대 음압과 최소음압의 비, 정상파비를 이용하여 흡음 계수를 구했다. 그 결과 흡음재의 흡음 특성은 진동수, 흡음재으 lwowlf, 두께 및 다공성에 크게 의존해 스폰지, 유리 섬유 등의 흡음 효과가 좋게 나타났으며 특히 같은 두께의 동일 흡음재일지라도 흡음재 뒷면의 공기층을 적절리 조절함으로써 특정 진동수 근처에서의 흡음 효과를 증대시킬 수 있었다.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.194-196
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• 2005

Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of thinning defects simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided plate waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of thinning defects. Measurement of the mode group velocity can be also used to quantify of thinning depth.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1014-1019
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• 2003

It seems inevitable for residential buildings to be high-rise and allocated near traffic roads due to the overcrowding in urban area. Acoustic environment in those area has been seriously deteriorated by the increase of traffic vehicles. Commonly used sound barriers have a limitation in controlling noise due to diffraction noise of sound barrier. Hence sound barrier is not effective to attenuate noise especially for the residential units in high level. This work aims at evaluating noise reduction according to the tunnel section shape by using 1/5 scale model. We carried out a number of field measurements for 1/5 scale model of Noise Barrier Tunnel with various sectional shape. The results from predictions and the measurement show generally good agreement.

• Speech Sciences
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• v.12 no.4
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• pp.77-92
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• 2005

Voice is made by systemic interaction of respiration, vocalization, articulation and resonation. There is no existing multi-channel voice analysis system to assess voice and respiration simultaneously. The most existing systems consist of. vocal fold vibration measurement such as stroboscopy, EGG (electroglottography) or laryngeal electromyography and voice analysis system. Since respiration has close relationship with voice simultaneous analysis of both vocal cord vibration and respiration are essential. In this study, a four channel integrated system are developed for acoustic analysis through microphone, vocal fold vibratory analysis using EGG, and respiratory analysis using two channel RIP (respiratory inductive plethysmography).

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.201-204
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• 2008

The use of the pulsed electro acoustic (PEA) method allowed us to perform the direct observations of spatio-temporal charge distributions in Electric double layer capacitors (EDLCs) based on polarizable nanoporous carbonaceous electrode. The negative charge density became the maximum, about 205 C/$m^3$ at the region where was near to collector layer in EDLCs for case $V_{DC}$ = 2.5 V, while the positively charged density became the maximum, about 61.1 C/$m^3$ at the region where it was located around the cathode layer. The PEA measurement used here is a very useful method to quantitively investigates the spatio-temporal charge distribution in EDLCs.

• KIEAE Journal
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• v.9 no.5
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• pp.63-68
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• 2009

As with the disappearance of a living room window due to the trend in apartment housing construction that prefers a larger, expanded living room, the sound insulation performance of the balcony window is becoming an important factor to determine the level of indoor noise at an apartment unit. Considering that the indoor noise inside an apartment unit is mandated by law at or below 45dB(A), the balcony window is increasingly assuming an even more important role. Sound insulation performance of the window was measured by examining differences in data involving varying angles of incidence of the sound source as obtained from the same balcony window. Also, acoustic intensity measuring was performed at and around the window to determine its sound insulation quality. Results of measuring on the sound source's angles of incidence indicated that the performance showed some differences in lower frequency ranges, though with no significance. Intensity measuring results showed that the sound insulation performance was reduced near the connection part of the window and the window frame.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.169-172
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• 1999

Recently, the wavelet transform has been a new and powerful tool for signal processing. It is more suitable specially for the feature extraction and detection of non-stationary signals than traditional methods such as, the Fourier Transform(FT), the Fast Fourier Transform(FFT) and the Least Square Method etc. because of the characteristic of the multi-scale analysis and time-frequency domain localization. The wavelet transform has been developed for the analysis of PD pulse signal to raise in the progress of insulation degradation. In this paper, the wavelet transform was applied to one foundational method for feature extraction. For the obtain experimental data, a computer-aided partial discharge measurement system with a single acoustic sensor was used. If we are applying to the neural network method the accumulated data through the extracted feature, it is expected that we can detect the PD pulse signal in the insulation materials on the on-line.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.38-46
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• 1996

This paper discusses the feasibility of Ultrasonic Nondestructive Evaluation (UNDE) technique for sport weld quality. Ultrasonic c-scan image assisted by image processing technique was used for Nondestructive Evaluation(NDE) of spot weld quality. Ultrasonic testing results obtained were confirmed and compared by Optical Microscope and SAM(Scanning Acoustic Mircroscope) observation of the spot-weld cross section, The results show that the nugget dinameter can be successfully measured with the accuracy of 0.5mm. It was ascertained that ultrasonic c-scan technique is very effective method for the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget. Additional support for the above conclusions is provided by the results for galvanized steel. The ultrasonic results for galvanized welds generally correspond to the results for uncoated steel. Finally, it was found that the above-mentioned technique can be sufficiently applied to NDE method for securing the Quality Assurance(QA) of spot welded products in production line.