• Journal of the Korean earth science society
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• v.37 no.7
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• pp.408-419
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• 2016

To investigate the in-situ sound velocity of sediment in the southwestern part of the East Sea, the laboratory sound velocity was measured using the pulse transmission technique. The sediment sound velocity measured in laboratory was corrected to in-situ sound velocity based on the seafloor temperature, seawater sound velocity, Kim et al. (2004) model, and Hamilton (1980) model. The distribution of the corrected in-situ sound velocity applying Kim et al. (2004) and Hamilton (1980) models reflects the characteristics of sediments of the study area and shows a similar distribution pattern. The correction for in-situ sound velocity was mostly influenced by seafloor temperature. Then, correction of sound velocity using seafloor sediment temperature data should be accomplished for conversion of laboratory data to in-situ sound velocity.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.73-80
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• 2006

In order to compute the radiated sound from a vibrating structure, the Rayleigh's integral equation has to be derived from the Helmholtz equation using Green's function. Generally, the surface velocity in the Rayleigh's integral equation uses the root mean square(rms) velocity. The calculation value is too large, because it's not considered cancelation. On the other hand. using the complex velocity, the sound pressure is calculated too small, because it considers that sound is perfectly canceled out. Therefore, this thesis proposes a correction factor(CF) which considers vibration modes and the method by which to calculate the radiating sound pressure. The theoretical results are compared with the experimental values, and the proposed method can be verified with confluence.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.746-751
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• 1994

The four-terminal transmission matrix method has been widely used to estimate the insertion-loss. However, the predictins using the equations in the four-terminal transmission matrix method do not reflect a practical phenomenon accurately, In this paper, the correction method to derive the insertion-loss for a constant sound pressure source is presented. The method of correction to the four-terminal transmission matrix method was proposed by rewriting the real and imaginary parts as they depend solely on the flow velocity. Then the result was compensated for by adding the component of the temperature gradient.

• Fisheries and Aquatic Sciences
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• v.11 no.2
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• pp.103-112
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• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.152-155
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• 2005

Diesel particulate filter (DPF) is comprised of a number of capillary tubes enclosed by porous ceramic wails, shaped like a plugged duct. Hot gas flows through the DPF along with the exhaust noise from Diesel engine. Based on previous works on the sound propagation through DPF, in this study, losses at entrance, exit, and ceramic walls are considered and the gradients in temperature and flow velocity are considered. Transfer matrix at entrance, monolith, and exit parts are obtained by employing the segmental approach in analyzing the sound propagation through DPF. The predicted transmission loss agrees very well with the empirical one, which is measured by the improved method with correction terms.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.259-265
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• 2005

To measure burning rate of solid propellants using ultrasonic technique, a special closed bomb and an ultrasonic and pressure measurement system are fabricated. During pressurization tests and burning tests on propellants, ultrasonic and pressure signal are acquired in realtime fashion by this system. Based on acquired signals, analysis programs using two different algorithm which can measure burning rates corresponding to pressures are compared. One algorithm is to correct sound velocity variation of propellants and solid couplant, another one is only to correct sound velocity variation of propellants. And accuracies of homing rates measured through these algorithms are calculated through comparison with homing rates measured using strand burner method.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.61-68
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• 2006

To measure burning rate of solid propellants using ultrasound, a special closed bomb and an ultrasonic and pressure measurement system are fabricated. During pressurization tests and homing tests on propellants, ultrasonic and pressure signal are acquired in real time fashion by this system. Based on acquired signals, analysis programs using two different algorithm which can measure burning rates corresponding to pressures are compared. One algorithm is to correct sound velocity variation of propellants and solid couplant, another one is only to correct sound velocity variation of propellants. And accuracies of homing rates measured through these algorithms are calculated through comparison with the burning rates measured using strand burner method.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.2
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• pp.115-124
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• 2017

This study was to develop the balance insole system for detecting and improving the muscle imbalance of left and right side in lower limbs. We were to verify the validation of balance insole system by analyzing the strategy of muscular activities and foot pressure according to sound feedback. We developed the balance insole based FSR sensor modules for estimating the muscle imbalance using detecting foot pressure. The insole system was FPCB have 8-spot FSR sensor with sensitivity range of 64-level. The participants were twenty peoples who have muscle strength differences in left and right legs over 20%. We measured the muscular activity and foot pressure of left and right side of lower limbs in various gait environment for verifying the improvement effect of muscle imbalance according to sound feedback. They performed gait in slope at 0, 5, 10, 15% and velocity at 3, 4, 5km/h. The result showed that the level of muscle imbalance reduced within 30% for sound feedback of balance insole system contrast to high level of muscle imbalance at 169.9~246.8% during normal gait for increasing slope and velocity. This study found the validation of balance insole system with sound feedback stimulus. Also, we thought that it is necessary to research on the sensitivity of foot area, detection of muscle imbalance and processing algorithm of correction threshold spot.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.525-536
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• 2014

In this paper, GUI program for microspeaker system simulation program was developed and verified through closed box, vent box and 6th order bandpass enclosure system. By using the pseudo loudspeaker model concept, TS parameters and rear volume of microspeaker were identified. Their suitabilities were proved by comparing test results with simulations of electrical impedance and sound pressure response curves for the three box types; closed box, vent box and 6th order bandpass box. Also, MSSP was found to be effective regardless of the microspeaker's shape, either circular or rectangular shape. MSSP can be used for the microspeaker system simulation, and can give a general prediction of such as; sound pressure level curve, electrical impedance, diaphragm velocity and displacement curve according to multiple design parameters; diaphragm mass, compliance, force factor, front and rear volume, front and rear port's diameter and length.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.433-436
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• 2004

퇴적물의 음파전달속도에 크게 영향을 주는 온도변화에 따른 속도변화를 측정한 결과 기존에 제시되었던 값들보다 약간 낮은 값을 보여주었으나 큰 차이를 보이지는 않았다. 결국 해양퇴적물의 온도에 따른 속도 변화율은 해수에서의 변화율과 거의 유사한 것으로 보아 해양퇴적물의 경우 온도에 따른 속도 변화는 공극수의 음향특성에 크게 영향을 받는 것으로 보인다. 서로 다른 퇴적물 유형에 대하여 온도에 따른 속도변화를 조사한 결과도 절대값은 달라도 변화양상은 거의 유사한 것으로 나타났다.