• Journal of Korea Foundry Society
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• v.20 no.5
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• pp.344-353
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• 2000

In order to find out the casting conditions of the thin wall stainless steel exhaust manifold for automobile, the melt flow and solidification behavior simulated by the Z-CAST program were evaluated, and experimental casting result on the test casting and exhaust manifold of SSC13 alloy were investigated. From the results of this study, it was shown that the calculated results on fluid flow were in good agreement with practical thin wall test castings under the same casting conditions, as pouring metal is austenitic stainless steel(SSC13) and pouring temperature is 1575, 1630, and $1665^{\circ}C$ respectively. That calculated result with designed thin wall exhaust manifold was predicted filling up into the mold cavity, and practical casting was sound. The solidification simulation was predicted shrinkages at the bosses for original exhaust manifold, and designed it without bosses was predicted no defect. Therefore practical exhaust manifold casting was sound and in good agreement with calculated solidification results.

• Phonetics and Speech Sciences
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• v.4 no.3
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• pp.13-23
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• 2012

The sound /w/ has been traditionally regarded as an independent segment in Korean regardless of the phonological contexts in which it occurs. There have been, however, some questions regarding whether it is an independent phoneme in /CwV/ context (cf. Kang 2006). The present pilot study examined how Korean /w/ is realized in $/S^*wV/$ context by performing some perception tests. Our assumption was that if Korean /w/ is a part of the preceding complex consonant like $/C^w/$, it should be more or less uniformly articulated and perceived as such. If /w/ is an independent segment, it will be realized with speaker variability. Experiments I and II examined the identification rates as "labialized" of the spliced original stimuli of $/S^*-V/$ and $/S^{w*}-^wV/$, and the cross-spliced stimuli $/S^{w*}-V/$ and $/S^*-^wV/$. The results showed that round qualities of /w/ are perceived at significantly different temporal point with speaker and context variability. We therefore conclude that /w/ in $/S^*wV/$ context is an independent segment, not a part of the preceding segment. Full-scale examination of the production test in the future should be performed to verify the conclusion we suggested in this paper.

• Journal of Korea Multimedia Society
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• v.14 no.11
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• pp.1507-1515
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• 2011

As the first step in research for sound synthesis of Pyungjong, timbre was analyzed by FFT analysis. There was no significant difference in the pitch of scale between modern Pyungjong and western twelve-tone equal temperament scale. The timbre of Pyunjong chagnes over time. When striking Pyunjong, the noises to be generated across all frequencies will disappear in a short period of time, and a unique partial only is left. Then it disappear from the partial of high frequency components in order, and two partials remain at release time. At this time, the beating is occurring by the frequency of the remaining partial. Pyungjong used in this study is relatively a recently manufactured Pyungjong, and for original sound synthesis of Pyungjong, a study of ancient Pyungjong's timbre should be additionally conducted later.

• Speech Sciences
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• v.15 no.3
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• pp.39-51
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• 2008

Formant measurements are one of the most important factors to objectively test cross-linguistic differences among vowels produced by speakers of any given languages. However, many speech analysis softwares present erroneous estimates and some researchers use them without any verification procedures. The purposes of this paper are to examine formant measurements of complex waves which were synthesized from the average formant values of five Korean vowels using three default methods in Praat and to verify the measured values of the five vowels produced by 20 students using one of the methods. Variances along the time axis are discussed after determining absolute difference sum from the 1/3 vowel duration point. Results show that there were smaller measurement errors by the burg method. Also, greater errors were observed in the sl or lpc methods mostly caused by the inappropriate formant settings. Formant measurement deviations were greater in those vowels produced by the female students than those of the male students, which were mostly attributed to the settings for the vowels /o, u/. Formant settings can best be corrected by changing the number of formants to the number of visible dark bands on the spectrogram. Those results suggest that researchers should check the validity of the estimates from the speech analysis software. Further studies are recommended on the perception test of the original sound with the synthesized sound by the estimated formant values.

• Proceedings of the KSPS conference
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• 1996.10a
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• pp.43-52
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• 1996

This paper deals with the nature and function of intensification in Korean in a wider scope of intensification which was not paid proper attention including intensification in the initial position as well as middle position. Unobserved new areas of intensification in the initial position are paid more attention like sound split of polysemy e.g. (s'eda), (kyongk'i) by means of intensification and north Korean application of intensification on (wonsu) and intensification of borrowed English. The recent phenomenon of ‘gwua’ intensification is experimented on two groups of people, young students and old people beyond 65 years old by means of sociolinguistic analysis. The result shows that its intensification is a form of student violent power and a mark of extreme solidarity among activist students. Thirty three university students(male 16, female 17) are asked to explained to write the meanings(feelings or when to use, etc.) of the words which have normal form and intensified forms. The results show intensification attaches the meaning of ‘emphasis,’ to bring the extremely polarized emotion: samll to the smallest, exact to the perfect exactness, bad to the worst feeling. Four words are being split to express different meaning with the word intensified. In conclusion, the nature of so called saisiot(t) e.g. intensification is voiceless tensed pause and its functions are the polarization of the original meaning of the word, sound split of polysemy and attachment of social values by intensification.

• Advances in aircraft and spacecraft science
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• v.6 no.6
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• pp.443-461
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• 2019

This communication investigates exact and distorted similitudes and the related scaling laws for the analysis of both dynamic response and radiated power of rectangular plates. The response of a given panel in similitude from another one is determined from a generalization of the modal approach, allowing the use of mode shapes, natural frequencies and finally radiation functions in order to establish appropriate scaling laws. Analytical models of simply supported rectangular plates are used to produce both original and replica model responses under point mechanical excitation. Emphasis is then especially put on laboratory experiments which are performed on baffled simply supported aluminum panels under mechanical excitations. All the six possible scaling directions, i.e. predicting a plate vibroacoustic reponse from another plate, are reported. All obtained results show that structural response or radiated sound power of a given plate can be both recovered with satisfactory accuracy by using the related scaling laws, even if parent models are used.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.559-564
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• 2002

Cross-talk cancellation, inverse filter design or deconvolution in a generic term, is a vital process for a virtual sound realization in the stereo sound reproduction system. Most, if not all, of the design algorithms available for the inverse filter are based on a linearized model of the real physical plant. The result of such a plant-based design method, which may be referred to here as the indirect method, is biased due to both modelling and inversion errors. This paper presents a novel direct cross-talk cancellation method that may be free from the inversion error. The direct method can directly models the inverse filter by a suitable rearrangement of the input and output ports of the original plant so that no inversion is required here. Advantages are discussed with various experiments in an anechoic chamber using a PC soundcard. Binaural reproduction tests conducted showed that the conventional indirect method yields about 8 % reproduction performance error on both ear positions, whereas the direct method offers about 3 %.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.4
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• pp.292-300
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• 1993

Acoustical imaging has made brilliant progress in the medical science field, and has also made much progress in the nondestructive testing and under water acoustics applications since doctor Dussik brother has studied about possibilities of making images of brain by recording variations in the intensity of ultrasonic beam from head in 1937. In this paper an acoustical image is reconstructed with the power spectra analysed by impulse ultrasound wave generated by electrodynamic transducer(EDT). The EDT generates the impulse ultrasound of 77KHz in center frequency and 120KHz in bandwidth at -20dB by 1200V exciter in this experiment. The impulse ultrasound has the dominant frequency components of 47KHz, 177KHz, 110KHz and 155KHz. The U shape object is adopted in making an acoustical image. The resulted spectral acoustical images are different from the optical view of the U shape object. However the image reconstructed from 110KHz spectrum is very similar to the original optical shape of the object. Even KHz level impulse sound of 70$\mu$sec pulse width is found to be useful in reconstructing acoustical imaging improvement.

• Proceedings of the IEEK Conference
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• summer
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• pp.244-248
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• 2004

This paper proposes a new noise cancellation method for speech recognition in noise environments. We determine the time adaptive threshold value using standard deviations of wavelet coefficients after wavelet transform by frames. The time adaptive threshold value is set up by using sum of standard deviations of wavelet coefficients in cA3 and weighted cD1. cA3 coefficients represent the voiced sound with lower frequency components and cD1 coefficients represent the unvoiced sound with higher frequency components. In experiments, we removed noise after adding white Gaussian noise and colored noise to original speech. The proposed method improved SNR and MSE more than wavelet transform and wavelet packet transform does. As a result of speech recognition experiment using noise speech DB, recognition performance is improved by $2\sim4\;\%.$

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.241-242
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• 2006

MPEG Surround is an audio coding technology that represents multi-channel audio signal with downmixed audio signal(s) and very low bitrate side information based on Binaural Cue Coding. The side information consists of Inter-Channel Level Difference, Inter-Channel Correlation, and payloads. These two parameters are correspondent to the well-known spatial parameters in psycho-acoustics, Inter-aural Level Difference (ILD) and Inter-Aural Cross Correlation (IACC). Though ICLD is to provide perceptually equivalent ILD to the listener, however, the ILD of the original multi-channel audio signal and that of the MPEG Surround encoded signal was different. The difference between two ILD values is defined as ILD Distortion (ILDD). This paper provides how ILDD can be applied to enhance sound quality in MPEG Surround and how much ILDD is decreased.