• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.22-32
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• 2011

The present study examined the effects of the complexity of the 3D models on the results of acoustic simulation which is the predominant tool of the acoustical design of buildings. Also, the effects of the 3D model on the auralized sounds were investigated. In order to carry out the study, four 3D models with different levels of complexity were introduced for a real auditorium which have different numbers of surfaces in the persuit of the guidance of odeon room acoustic software. The set-up of models was also based on the level of transition order of the program. And the acoustic experiments were performed measuring room acoustic parameters including SPL, RT, C80, D50. Acoustic computer simulations were performed using four different models. Then, the results of the computer modeling were compared with the measured acoustical parameters. In addition, sound sources were recorded in the field and auralized sounds were made in convolution with the impulse source made from acoustic modeling. Then, subjective tests were undertaken using auralized sounds. As the results, it was found that the result of the acoustic simulation were closer to the real room acoustic properties when 3D model was more particularly made. For the subjective test, the listening materials were acknowledged as similar with the real sound source when more complex 3D model was used. Then, it could be concluded that the complexity of the 3D model affects the results of the acoustic modeling as well as subjective tests.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.657-673
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• 2019

A monitoring method based on acoustic emission (AE) sensor has been widely used to evaluate the damage of structures in underground rock. The acoustic emission signal generated from cracking in material is analyzed as various acoustic emission parameters in time and frequency domain. To investigate from initial crack generation to final failure of rock material, it is important to understand the characteristics of acoustic emission parameters according to the stress ratio and rock strength. In this study, uniaxial compression tests were performed using very strong and weak rock specimen in order to investigate the acoustic emission parameters when the failure of specimen occurred. In the results of experimental tests, the event, root-mean-square (RMS) voltage, amplitude, and absolute energy of very strong rock specimen were larger than those of the weak rock specimen with an increase of stress ratio. In addition, the acoustic emission parameters related in frequency were more affected by specification (e.g., operation and resonant frequency) of sensors than the stress ratio or rock strength. It is expected that this study may be meaningful for evaluating the damage of underground rock when the health monitoring based on the acoustic emission technique will be performed.

• Korean Journal of Otorhinolaryngology-Head and Neck Surgery
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• v.60 no.9
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• pp.454-462
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• 2017

Background and Objectives The present study aimed to investigate the effects of penetration/aspiration (P/A) on voice acoustic parameters. Subjects and Method Twenty-seven patients were analyzed with the videofluoroscopic swallowing study (VFSS) and then divided into two groups based on the modified Penetration and Aspiration Scale results. Ten patients (5 males and 5 females) were included in the Non-P/A group, and 17 patients (12 males and 5 females) in the P/A group. Stroke was the major cause of swallowing disorders. Three sustained /a/ vowels recorded in pre- and post-VFSS were analyzed. Mann-Whitney U-test was used to compare acoustic values before and after VFSS, and the receiver operating characteristics (ROC) curve with combination of significant parameters was also conducted. Results Among acoustic parameters, the length of analyzed sample (p=0.010), number of segments computed (p=0.018), total number detected pitch periods (p=0.017), and second formant (p=0.013) in pre- and post-VFSS were significantly different between Non-P/A and P/A groups. In the P/A group after VFSS, the means of these significant parameters decreased. According to ROC combined with four significant parameters, the probability of predicting P/A condition was 84% (p=0.005), the sensitivity was 80%, and the specificity was 80%. Conclusion Voice acoustic analysis can reflect voice changes by penetration/aspiration and the combination of significant parameters can also detect swallowing disorders. Therefore, voice analysis can be a reliable screening tool for patients with swallowing disorders.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.5
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• pp.580-585
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• 1988

In this paper, a low frequency acoustic microscope system has been built for the purpose of detecting subsurface defects in materials. The lateral resolution of acoustic microscope is studied and analyzed in order to evaluate that system performance. And a NDE technique is demonstrated by using this system. In the focused and defocused mode of operation, the acoustic microscope system showed in experiment that its lateral resolution was about 0.5 mm at a frequency of operation of 3MHz on a fused-quartz sample with seeded circular cracks ranged in size from 0.2 mm to 1.0 mm in diameter wihtin 1 mm of the surface. It also showed the acoustic image of 100 won coin with fine contrast.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.43-48
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• 2002

Acoustic modes of a vehicle compartment dominate the noise characteristics of the vehicle system in the low frequency range. Vehicle compartments have head liner and air gap of proper thickness to mount a interior lamp, as well as to have a good sound insulation and absorption performance. This study estimates the acoustic modal property of the medium size passenger car by experiment and by finite element analysis and also, investigates the effect of the head liner on the acoustic mode of the passenger compartment to obtain useful information for low noise compartment design.

• Proceedings of the KSPS conference
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• 2002.11a
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• pp.145-149
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• 2002

This study was performed to find out changes in acoustic measurements of voice after eating egg, apple and pear. Ten college students vocalized /a/ before and after eating egg, apple and pear. Dr. Speech was utilized to obtain changes of subjects's acoustic measurements. A t-test was peformed to determine acoustic changes of voice before and after eating egg, apple and pear. No significant difference was observed in acoustic measurements before and after eating egg, apple and pear. However, the subjects seemed to show some improvements in Jitter, HNR, and NNE in the order of egg, apple, and pear even though they did not reach a statistical significance. It was concluded that a more systematic research paradigm is needed in order to objectively reject or substantiate a variety of conceptions on food items and their effects on voice.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1069-1074
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• 2004

This study investigated the effect of pressure variations on augmentation of heat transfer when the ultrasonic waves were applied. The augmentation ratio of heat transfer was experimentally investigated and was compared with the profiles of pressure distributions calculated applying a coupled finite element-boundary element method (coupled FE-BEM). As the ultrasonic intensities increase from 70W to 340W, the velocity of the liquid paraffin is found to increase as well as kinetic energy, This physical behavior known as quasi-Eckart streaming results from acoustic pressure variations in the liquid. Especially, the higher acoustic pressure distribution near two ultrasonic transducers develops more intensive flow (quasi-Eckart streaming), destroying the flow instability. Also, the profile of acoustic pressure variation is consistent with that of augmentation of heat transfer. This mechanism is believed to increase the ratio of hear transfer coefficient.

• Ocean Science Journal
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• v.41 no.4
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• pp.195-199
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• 2006

Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water. Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125-130 (2001)] reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation. It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing in the ocean.

• MALSORI
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• no.64
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• pp.1-14
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• 2007

The purpose of this study was to examine the acoustic perception different by formants change for profoundly hearing impaired children with cochlear implants. The subjects were 10 children after 15 months of experience with the implant and mean of their chronological age was 8.4 years and Standard deviation was 2.9 years. The ability of auditory perception was assessed using acoustic-synthetic vowels. The acoustic-synthetic vowel was combined with F1, F2, and F3 into a vowel and produced 42 synthetic sound, using Speech GUI(Graphic User Interface) program. The data was deal with clustering analysis and on-line analytical processing for perception ability of acoustic synthetic vowel. The results showed that auditory perception scores of acoustic-synthetic vowels for cochlear implanted children were increased in F2 synthetic vowels compaire to those of F1. And it was found that they perceived the differences of vowels in terms of distance rates between F1 and F2 in specific vowel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.618-622
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• 2007

Recently, in accordance with elevation of the consciousness level of citizens, the desire for cultural life is on increasing, and according to this trend, it is the real fact that the demand of the Grand Performance Hall where various cultural events can be performed, is also on increasing. However, since the Grand Performance Hall in view of its distinctiveness, is required of the repletion or abundance of sound, it could be said that the sufficient examination and planning about this are indispensable from the designing stage. On this viewpoint, this Study has intended to design the performance hall that maintains the optimized acoustic capacity through an acoustic simulation for the object of the grand performance hall on the step of construction. After completion of the construction for Grand Performance Hall hereafter, if compare the data analyzed in such way with the actually measured acoustic performance, it is considered that the more optimized architectural acoustic design could be achieved.