• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.8
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• pp.539-545
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• 2015

Intense acoustic load is generated when a launch vehicle lifts off, causing the damaging vibrations at the launch vehicle or satellite within the fairing. This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. As a test example, the lift-off acoustic load on the Korean launch vehicle, NARO, is predicted by the existing calculation tool, the modified Eldred's second method. Although the acoustic sources, assumed as point sources, are to be located along the center line of the exhaust plume when using the Eldred's prediction method, the exact location of the deflected center line of exhaust gas flow is not usually known. To search for the most appropriate source positions, six models of source line distribution are suggested and the acoustic load prediction results from these models are compared with the actual measurements. It is found that the predicted sound pressure spectrum of the Naro is the most similar to the measured data when the centerline of the turbulent kinetic energy contour is used as the source line.

• Speech Sciences
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• v.10 no.4
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• pp.189-200
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• 2003

The objective of this study was to examine two new parameters by which we could screen people with malignant vocal folds. The new parameters were the difference sums and Pearson correlation coefficients between adjacent pairs of intensity level matrices of narrow-band spectra. Audio files from the Korean Disordered Speech Database were analyzed by Praat, a speech analysis software, to obtain matrices of 400 intensity levels at 16 time points of each sustained vowel spectra. We limited our study to 12 normal subjects and 20 patients with malignant vocal folds who recorded at least three Korean vowels at a sound-proofed booth in Busan National University Hospital. Results indicated that the average coefficients of the abnormal subjects were much lower than those of the normal subjects while the average difference sums of the patients were much higher than those of the normal ones. Also, we found that the degree of the malignancy of the vocal folds was related to the coefficients and sums. However, some subjects at the initial stages of cancerous vocal folds yielded almost comparable coefficients and difference sums to those of the normal speakers. Further studies on larger databases will be desirable to set certain criteria or threshold levels for screening people with vocal fold diseases.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1302-1309
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• 2014

In this paper, we propose a method to improve the performance of the direction-of-arrival (DOA) estimation of a speech source using a multiple signal classification (MUSIC)-based algorithm. Basically, the proposed algorithm utilizes a complex coefficient band pass filter to generate the narrow band signals for signal analysis. Also, reverberation component reduction and quadratic function-based response approximation in MUSIC spatial spectrum are utilized to improve the accuracy of DOA estimation. Experimental results show that the proposed method outperforms the well-known generalized cross-correlation (GCC)-based DOA estimation algorithm in the aspect of the estimation error and success rate, respectively.Abstract should be placed here. These instructions give you guidelines for preparing papers for JICCE.

• Speech Sciences
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• v.13 no.3
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• pp.49-65
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• 2006

Recently, several theories on the digital speech signal processing expanded the communication boundary between human beings and machines drastically. The aim of this study is to collect dialectal speech in Korea on a large scale and to establish a digital speech data base in order to provide the data base for further research on the Korean dialectal and the creation of value-added network. 528 informants across the country participated in this study. Acoustic characteristics of vowels and consonants are analyzed by Power spectrum and Spectrogram of CSL. Test words were made on the picture cards and letter cards which contained each vowel and each consonant in the initial position of words. Plot formants were depicted on a vowel chart and transitions of diphthongs were compared according to dialectal speech. Spectral times, VOT, VD, and TD were measured on a Spectrogram for stop consonants, and fricative frequency, intensity, and lateral formants (LF1, LF2, LF3) for fricative consonants. Nasal formants (NF1, NF2, NF3) were analyzed for different nasalities of nasal consonants. The acoustic characteristics of dialectal speech showed that young generation speakers did not show distinction between close-mid /e/ and open-mid$/\epsilon/$. The diphthongs /we/ and /wj/ showed simple vowels or diphthongs depending to dialect speech. The sibilant sound /s/ showed the aspiration preceded to fricative noise. Lateral /l/ realized variant /r/ in Kyungsang dialectal speech. The duration of nasal consonants in Chungchong dialectal speech were the longest among the dialects.

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.4
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• pp.259-270
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• 2003

In order to properly design warning sounds that are affectively suitable to computer users, warning sounds used in Windows operating system were analyzed in terms of their sound properties; frequency band, spectral characteristics and physical intensity. A total of 36 warning sounds (3*4*3) were generated and tested with respect to three experimental variables. Among 178 collected affective adjectives that are related to hearing and sounds, seven representative affective adjectives were abstracted by statistical grouping techniques. In the experiment, subjective preference tests were performed for the 36 warning sounds according to the seven affective factors. From the result, the affective factors were again grouped into three major factors and the 60dB boost-type warning sounds at the low frequency band were, in general, the most preferred. followed by the 70dB cut-type sounds at the middle frequency band. These warning sounds have a characteristic of boost power spectrum below 1000Hz frequency band and received good scores on simplicity, clarity and accurateness.

• The Journal of the Acoustical Society of Korea
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• v.25 no.1
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• pp.43-48
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• 2006

When the vibration of a phantom induced by Extracorporeal Shock Wave Lithotripter (ESWL) was investigated. we found the fact that the Peak frequency in the Power spectrum shifts from high frequency to low frequency as the number of shots increases[2]. The fact was confirmed experimentally by detecting the peak frequency obtained from the vibrations of bronze models[3]. This Paper investigates the experimental results. For the Purpose. we carried out the computer simulation using the finite element method. It is found that the results from the experiments are computer by computer simulation.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.121-128
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• 2010

This study is to analyze change of connectivity between brain positions caused by relaxation through EEG coherence. EEG spectrum analysis method has been used to analyze brain activity when relaxation was experienced. However, the spectrum analysis method has a limit that could not observe interactive reaction between brain-functional positions. Therefore, coherence between positions was analyzed to observe connectivity between the measurement positions in this study. Through the method, the reaction of the central nervous system caused by the emotion change was observed. Twenty-four undergraduates of both genders(12 males and 12 females) were asked to close their eyes and listen to the sound. During experiment, EEG was measured at eight positions. The eight positions were F3, F4, T3, T4, P3, P4, O1, and O2 in accordance with International 10-20 system. The sounds with white noise and without were used for relaxation experience. Subjective emotion was measured to verify whether or not they felt relaxation. Subjective emotion of participants were analyzed by ANOVA method(Analysis of Variance). In the result, it was proved that relaxation was subjectively evoked when participants heard sound. Accordingly, it was proved that relaxation could be enhanced by the mixed white noise. EEG coherence between the measurement positions was analyzed. T-test was performed to find its significant difference between relaxation and not-relaxation. In the results of EEG coherence, connectivity with occipital lobes has been increased with relaxation, and connectivity with parietal lobes has been increased with non-relaxed state. Therefore, brain connectivity has shown different pattern between relaxed emotion and non-relaxed emotion.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.4
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• pp.163-168
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• 1987

The underwater observation of the ambient noise and the noise generated by the engine revolution in a ship was carried out in July to August, 1984, 1985 and 1987, near around some ports and in the Eastern Sea of Korea. Vertical distribution of the sound pressure of both noises were observed and the spectrum characteristics were analysed and compared. The results obtained are summarized as follows: 1. Sound pressure level of the ambient noise at 5m deep layer in calm sea condition (wind speed 0-2m/s) near around the ports were observed as 108dB at the eastern part of Pusan port, 106dB at the southern part of Pusan port and 101dB at Kuryongpo port. It shows that the level near around the large port which contains much noisy resources is higher than the small port. The level at 5m deep layer in the open sea, in the mid-region between Korean Peninsula and Ulnung Island was observed as 100dB. It mean that the level in the open sea is lower than that around the ports. The level at 20m and 70m deep layer were 1-2dB lower than that at 5m deep layer, and that at deeper layer than 100m was almost constantly 100dB around. 2. Sound pressure level of the ambient noise at 5m deep layer in windy open sea condition (wind speed 10-15m/s) was 108dB, and was gradually decreased in accordance with the increase of depth with representing 100dB at 70m deep layer and that at deeper layer was almost constantly 100dB. The level of the noise generated by engine revolution was 146, 125, 112, 110, 104dB at 5, 50, 100, 150 and 200m deep layer respectively. It means that the level decrease with the depth. 3. Spectrum level of the ambient noise at 5m deep layer with the frequency band of 10 Hz, 100 Hz, 1 KHz, 10 KHz, in the windy sea condition were 86, 75, 61, 32dB respectively and the level of the noise generated by engine revolution was 105, 95, 86, 55dB respectively. It means that the latter are about 20dB higher than the former. The level of the former at 200m deep layer was 80, 68, 47, 26dB and the latter 82, 70, 59, 31dB. It means that the latter are about 4dB higher than the former.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.2
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• pp.103-109
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• 2016

Efficacy of cosmetics has been mainly evaluated by qualitative and quantitative methods based on visual sense, tactile sense and skin structure until now. In this study, we suggested a novel evaluation method for skin status based on sound; measuring and analyzing the rubbing noise generated by applying cosmetics. First, the rubbing noise was measured at a close range by a high-sensitivity microphone in anechoic environment, and the noises were analyzed by 1/3 octave band analysis in frequency-domain. Three conditions, 1) before washing, 2) after washing and 3) after application of cosmetics, were compared. As a result, sound pressure level (SPL) of rubbing noise after washing was larger than that of before washing, and the SPL of rubbing noise after cosmetic application was the smallest. Furthermore, the energy of rubbing noise after application was higher than that of the before and after washing conditions in a low frequency band (lower than 2 kHz region). Conversely, the energy of rubbing noise after application was much lower than the others in a high-frequency band (upper than 2 kHz region). This change of energy distribution was described as a balloon-skin model. High SPL in the low frequency region after the cosmetic applications was due to the increase of "flexibility index", while SPL in the high frequency region significantly decreased because of the attenuation which is related to "softness index". Therefore, we developed two indices based on the spectrum-energy difference for evaluating skin conditions. This proposed method and indices were verified via skin flexibility and roughness measurement using cutometer and primos respectively. These results suggest that acoustic measurement of skin friction noise may be a new skin status evaluation method.

• Journal of the Korea Society of Computer and Information
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• v.19 no.6
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• pp.93-100
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• 2014

The objective of this study is to propose the measurement system implementation method for the evaluation and measurement of the indoor-impulsive over 170 dB noise source. For the purpose of measuring impulse noise, design and implementation constructed followed subsystems of the testing center, microphone, ear simulator, head and torso simulator and so on. Measurement systems for the accuracy and reliability of impulse noise are implemented when measuring 3 ways of measurements method by the simultaneous measurement system design. For the accuracy and reliability of three mutually indoor-impulse noise measurements were compared, three kinds of measuring methods in accordance with the peak sound pressure level and octave band. Comparing the results of data, the indoor-impulse noise by analyzing a frequency characteristic was validated in difference for the statistical significance. Result are determined by the influence of the reflected wave. Therefore, the flexible size of the interior test site while interior impulse noise measurement system was constructed. Throughout this system can be affected by parameters that are the impulse noise source and the corresponding frequency-characteristic analysis to determine the spectrum of the reflected wave. And, in the near future, indoor impulse noise measurement systems for acquisition and analysis are utilized in useful data.