• The Journal of the Acoustical Society of Korea
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• v.13 no.5
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• pp.40-50
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• 1994

In this paper, the sensitivity compensation method for three-dimensional acoustic intensity probe in the higher frequency range has been studied. The measurement error in the higher frequency range is generated from the phase mismatch between microphone's signals of the probe. If the wavelength of sound signal measured is less than those of the distance between microphones of the probe, that is, the higher frequency of the sound signal, the bigger measurement error is generated. In this study, we proposed the compensation methods for one-dimensional acoustic intensity probe with two-microphones, and the efficiency of those methods were investigated by numerical calculation of computer. It was most effective method to compensate the phase mismatch between microphone for the acoustic intensity probe was investigated for the sound estimated. and the efficiency of this method in a three-dimensional probe was investigated for the sound wave travelling in the arbitrary direction by numerical calculation of computer. In this result, the efficiency was proved that, for the measurement error of 1dB or less with the three-dimensional probe of 60mm space, the frequency should be less than 1.2kHz without the error compensation method, but the frequency increased up to 2.8kHz with the error compensation method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.114-122
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• 1999

Reignition as special cases of acoustic pressure responses of flame are numerically studied by employing methanol droplet flame as a laminar flamelet. Quasi-steady flame responses occur in the range of small amplitude, low frequency oscillation. Reignition phenomena can occur when, by increasing the frequency of large amplitude acoustic pressure, the magnitude of characteristic acoustic time is the same order of that of characteristic reaction time of flames. And more increasing of amplitude of acoustic pressure induces the direct extinction of flame. Flame can sustain its own intensity even under the steady extinction temperature in case of high frequency acoustic oscillation, and this tendency is remarkable with increasing frequency. Reignition regime with respect to amplitude and frequency of acoustic pressure doesn't exist in low frequency($10^2$ Hz, in this study), but broadens with frequency of acoustic pressure.

• Journal of the Korea Society of Computer and Information
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• v.19 no.11
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• pp.159-166
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• 2014

In this paper, we examine the role of emotional acoustic cues including both prosody and voice quality parameters for the modification of a word sense. For the extraction of prosody parameters and voice quality parameters, we used 60 pieces of speech data spoken by six speakers with five different emotional states. We analyzed eight different emotional acoustic cues, and used a discriminant analysis technique in order to find the dominant sequence of acoustic cues. As a result, we found that anger has a close relation with intensity level and 2nd formant bandwidth range; joy has a relative relation with the position of 2nd and 3rd formant values and intensity level; sadness has a strong relation only with prosody cues such as intensity level and pitch level; and fear has a relation with pitch level and 2nd formant value with its bandwidth range. These findings can be used as the guideline for find-tuning an emotional spoken language generation system, because these distinct sequences of acoustic cues reveal the subtle characteristics of each emotional state.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.386.2-386
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• 2002

This paper reports the performance and the Algorithm of an 1/3-octave band spectrum control system. The system is developed to provide various required spectrums in a high intensity acoustic chamber. The required spectrums, which usually comes from launch vehicle specification, starts from 25㎐ band and ends 10,000㎐. Short settling time is required to guarantee the safety of test objects and reduce the amount of operating gas. (omitted)

• Proceedings of the KSPS conference
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• 2006.05a
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• pp.101-104
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• 2006

The present study examined two acoustic characteristics(duration and intensity) of vowels produced by 4 cerebral palsic adults and 4 nondisabled adults in conversational and clear speech. In this study, clear speech means: (1) slow one's speech rate just a little, (2) articulate all phonemes accurately and increase vocal volume. Speech material included 10 bisyllabic real words in the frame sentences. Temporal-acoustic analysis showed that vowels produced by two speaker groups in clear speech(in this case, more accurate and louder speech) were significantly longer than vowels in conversational speech. In addition, intensity of vowels produced by cerebral palsic speakers in clear speech(in this case, more accurate and louder speech) was higher than in conversational speech.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.278-281
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• 2004

Multiple sound sources are controlled to enhance sound power within a zone of interest. The problem of enhancing acoustic variable can be regarded as an optimization problem, which seeks an optimal control input that maximizes the acoustic variable. It should be noted that enhancing sound power of a selected region requires both the magnitude and direction to be controlled. For this reason, two kinds of cost functions that can represent the spatially distributed intensity are defined. Theoretical formulation shows the possibility of sound power control in a zone, and the detailed procedures of the proposed method are validated by numerical simulations.

• Speech Sciences
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• v.13 no.3
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• pp.97-105
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• 2006

The objective of this study was to analyze the acoustic patterns of Japanese /t/ produced by 40 Korean speakers in order to find an effective method of teaching it to Koreans. The experimental data consisted of 400 /t/ phonemes in word initial or non-initial positions of 10 words. Informants were in their twenties and raised in Daejeon and the surrounding area. Results showed that there were distinctive trends in duration and intensity of the major and non-major groups productions. Both groups pronounced the phoneme longer than the native speakers with more open mouths but with less loudness. The formant analysis showed that F1 values of the Japanese /t/ pronounced by Japanese major group were lower than those of the non-major. Its F2 values by the major group were higher than those of the non-major, which would suggest that the Koreans produced the tongue blade in more frontal position than the native speakers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1253-1262
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• 2001

Experimental study is conducted to investigate the heat/mass transfer and flow characteristics for the flow over backward-facing step and cavities. A naphthalene sublimation method has been employed to measure the mass transfer coefficients on the duct wall and LDV system has been used to obtain mean velocity profiles and turbulence intensities. Reynolds number based on the step height and free stream velocity is 20,000 and St numbers of acoustic excitations given to separated flow are 0.2 to 0.4. The spectra of streamwise velocity fluctuation show a sharp peak forcing frequency for an acoustically excited flow. The results reveal that the vortex pairing and overall turbulence level are enhanced by the acoustic excitation and a significant decrease in the reattachment length and the increased turbulence intensity are observed with the excitation. A certain acoustic excitation increases considerably the heat/mass transfer coefficient at the reattachment point and in the recirculation region. For the cavities, heat/mass transfer is enhanced by the acoustic excitation due to the elevated turbulence intensity. For the 10H cavity, the flow pattern is significantly changed with the acoustic excitation. However, for the 5H cavity, the acoustic excitation has little effect on the flow pattern in the cavity.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.938-946
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• 1989

Using the CT specimen of carbon steel(SM45C), we estimated the fatigue crack propagation behavior in stable crack propagation range. Furthermore the fatigue crack propagation rate, Acoustic Emission(AE) count rate, and fractography characteristics were also compared among others. The following results were confirmed by experimental observation. Near-threshold stress intensity factor range(.DELTA. $K_{th}$) is influenced by stress ratio but not at the upper limit of stable crack propagation range. As stress intensity factor range(.DELTA.K) and(or) stress amplitude increase (s), both crack propagation rate(da/dN) and AE count rate(dn/dN) increase. Effective stress intensity factor range(.DELTA. $K_{off}$) determined from the crack closure point measurement by AE method is useful for the evaluation of fatigue crack propagation rate. Fractography in stable crack propagation range showed striation, and agreed with the crack propagation rate obtained either by experiment of by the results of microscopic measurements.s.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.2
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• pp.56-62
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• 1990

Surface Acoustic Waves(SAW) are generated on silicon wafer and $YZ-LiTaO_3$ substrate and are detected by noncontact method. As wave sources two kinds of transducers are used : the wedge-type of 20.0 MHz and fabricated Interdigital Transducer(IDT) of 20.8 MHz. SAW are modulated by the optical chopper frequency and are syncronized with a laser beam. In signal processing, intensity variations of light due to the intensity of SAW are analyzed using lock- in amplifier. From the results, corresponding to the applied input power, the intensity variations of a deflected light by corrugations on the substrates are increased and saturation phenomenon is observed.