• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.692-693
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• 2004

We introduce a new velocity sensor, micro-flown sensor, which was developed by H-E de Bree. The sound absorption coefficients of a fiber material with the conventional pressure microphones and the micro-flown sensors were measured and compared. The experimental results show that both sensors could be well applied to measure the sound absorption coefficient but the pressure sensor was rather stable than micro-flown sensor

• Proceedings of the IEEK Conference
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• summer
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• pp.237-243
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• 2004

A multichannel smart sound sensor capable to detect and identify sound events in noisy conditions is presented in this paper. Sound information extraction is a complex task and the main difficulty consists is the extraction of high­level information from an one-dimensional signal. The input of smart sound sensor is composed of data collected by 5 microphones and its output data is sent through a network. For a real time working purpose, the sound analysis is divided in three steps: sound event detection for each sound channel, fusion between simultaneously events and sound identification. The event detection module find impulsive signals in the noise and extracts them from the signal flow. Our smart sensor must be capable to identify impulsive signals but also speech presence too, in a noisy environment. The classification module is launched in a parallel task on the channel chosen by data fusion process. It looks to identify the event sound between seven predefined sound classes and uses a Gaussian Mixture Model (GMM) method. Mel Frequency Cepstral Coefficients are used in combination with new ones like zero crossing rate, centroid and roll-off point. This smart sound sensor is a part of a medical telemonitoring project with the aim of detecting serious accidents.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.792-796
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• 2003

In this paper, to detect external sound frequency on the latticed structure, fiber optic sensor net using Sagnac interferometer was fabricated and tested. The latticed structure fabricated with dimension of 50cm in width and 50cm in height, the optical fiber, 50m in length, distributed and fixed on the latticed structure. Single mode fiber, a laser with 1,550nm in wavelength, 2${\times}$2 coupler were used. External sound signal applied to the fiber optic sensor net and the detected optical signals were compared and analyzed to the detected microphone signals against time and frequency domain. Based on the experimental results, fiber optic sensor net using Sagnac interferometer detected external sound frequency, effectively. This system can be expanded to the structural health monitoring system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.569-576
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• 2004

In this paper, to detect external sound frequencies on the latticed structure, fiber optic sensor net using Sagnac interferometer was fabricated and tested. The latticed structure was fabricated with a dimension of 50 cm in width and 50 cm in height. The optical fiber of 50m in length was distributed and fixed on the surface of the latticed structure. Single mode fiber, a laser with 1,550 nm in wavelength, 2 ${\times}$ 2 coupler were used. External sound signal, 240 Hz, 495 Hz, 1.445 kHz, 2k Hz, applied to the fiber optic sensor net and the detected optical signals were compared to the detected microphone signals against time and frequency domains. Based on the experimental results, fiber optic sensor net using Sagnac interferometer detected external sound frequency, effectively. This system can be expanded to the structural health monitoring system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.81-84
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• 2007

In this paper, fiber optic sound and vibration monitoring sensor which is latticed shape structure based on Sagnac interferometer is fabricated and tested in laboratory conditions. To detect external vibrations surface mounted fibers on the latticed steel wire fence with a dimension of 170cm by 180cm is used. To detect external sound frequency the tightened fiber optic itself wire netting fence with a dimension of 50cm by 50cm is used. Experiments for the detection of the excited vibration and sound signals were performed. A small vibrator induced external vibration signal and it is applied to the latticed structure in the range of 100Hz to several kHz. External sound signal applied to the fiber optic sensor net using non-directional sound speaker. The detected optical signals were compared and analyzed to the detected both accelerometer and microphone signals in the time and frequency domain. Based on the experimental results, distributed fiber optic sensor using Sagnac interferometer detected effectively external vibration and sound signal and had a good performance. This system can be expanded to the monitoring of a significant system and to the structural health monitoring system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.202-204
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• 1995

An acoustic sensor using PVDF film is proposed in this paper. And its properties, such as sensitivity level, identification of sound source frequencies. and directivity, were experimented. Sensitivity level measured at the distance of 1[m] was limited in the range of ${\pm}$10dB. Adjacent three frequencies were also tested to identify the frequency of sound sources. In the range of audible frequencies, it could distinguish the frequencies of a complex sound. In addition, it was found that the sensor outputs were maximum in the coincided direction with a source, when directivity was experimented with three sound sources and FFT. The proposed PVDF film sensor has good characteristics of directivity and identifying ability as an acoustic sensor.

• 대한공업교육학회지
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• v.31 no.1
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• pp.185-199
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• 2006

In this paper, to detect lateral direction sound pressure fiber optic sensor using Fabry-Perot interferometeric sensor array was fabricated and experimented. This parallel sensor array composed of one light source and the light split into each sensor using directional coupler and to see the output signal the array system do not need any digital signal processor. As a lateral direction sound source arbitrary sound frequency of 100Hz, 200Hz, and 655Hz using by nondirectional speaker were applied to the array sensor which installed on $60cm{\times}60cm{\times}60cm$ latticed structure. The detected signals from the two sensors were analyzed in the time and frequency domains. It was confirmed that the suggested sensor array detected applied sound source well but there were a little amplitude differences in between the sensors. Because the sensor supported simply at both ends theoretical analysis was performed and its solution was suggested. To compare the theoretical and experimental results arbitrary sound frequency of 2kHz was applied to the sensor array. It shows that experimental results was good agreement with theoretical results.

• Physical Therapy Korea
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• v.8 no.3
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• pp.1-10
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• 2001

The purpose of this study was to compare the static pressure, dynamic pressure, dynamic pressure-time integral, relative impulse, and contact time between the sound lower limb and amputated lower limb in trans-tibial amputee subjects using Parotec system. Seventeen trans-tibial amputee subjects wearing endoskeletal trans-tibial prosthesis voluntarily participated in this study. The results were as follows: 1) In static standing condition, there were significantly higher static pressure in sound lower limb insole sensor of 10, 14, 15, 18, 19, 23, and 24 and in amputated lower limb insole sensor of 9, 12, and 16 (p<.05). 2) In dynamic gait condition, there were significantly higher dynamic pressure in sound lower limb insole sensor of 2, 18, 22, 23, and 24 and in amputated lower limb insole sensor of 5, 9, 10, 11, 12, 14, 15, and 16 (p<.05). 3) In dynamic gait condition, there were significantly higher pressure-time integral in sound lower limb insole sensor of 2, 4, 18, 19, 20, 21, 23, and 24 and in amputated lower limb insole sensor of 5, 11, 12, and 15 (p<.05). 4) In dynamic gait condition, there were significantly higher relative impulse in sound lower limb insole sensor of 18, 19, 20, 22, 23, and 24 and in amputated lower limb insole sensor of 5, 9, 10, 11, 12, and 15 (p<.05). 5) In dynamic gait condition, there was significantly higher percentage of contact time in push off phase of sound lower limb and in support phase of amputated lower limb (p<.05). These results suggest that trans-tibial amputee subjects had characteristics of shortened push off phase due to unutilized forefoot and of lengthened support phase with higher pressure in the midfoot.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1444-1450
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• 2013

Esophageal stethoscope is used for monitoring the heart sounds and breath sounds of patients during surgery under a general anesthesia. Recently, an electronic esophageal stethoscope (EES)[1] has been developed for the purpose of real-time monitoring these information visually. This system uses only a microphone as the sound sensor. A drawback of the EES system is that it may be difficult to distinguish the first sound ($S_1$) and the second sound ($S_2$) of heart, because their periods are irregular depending on patients. In this paper, we propose an improved EES system in which the infrasound is measured by adding a pressure sensor as well as a sound sensor. We investigate some correlations between the infrasound and characteristics of the heart sound. The proposed system has been tested on 15 patients. The results show that the new system is capable of detecting the first sound more reliably and easily determining the heart rate and breathing period.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.7
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• pp.626-633
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• 2012

In this paper, sound pressure sensitivity of the fiber optic acoustic sensor according to sensor direction and mandrel material were investigated experimentally. Three different directions were selected as stand, lay, and hole. Hollow cylinder type mandrel dimension is 30 mm in outer diameter, 45 mm in length, and 2 mm in thickness, and about 50 m optical fibers were wounded on the surface of the mandrel. Non-directional sound speaker was used as a sound source. Sagnac interferometer and single mode fiber, a laser with 1,550 nm in wavelength, $2{\times}2$ coupler were used. Based on the experimental results, lay direction's sensitivity is the highest in the frequency range of 2 kHz~4 kHz. 'PTFE+carbon' material is more sensitive than PTFE in the frequency range of 5 kHz~20 kHz. Sound pressure detection sensitivity depends on the mandrel direction and material under certain frequency.