• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.2 no.2
• /
• pp.29-36
• /
• 2009

The analysis of Radar signal, telecommunication, bioengineering, seismic, and acoustic signal is consist of the Non-stationary signal which has non-linear phase variation. Non-stationary signal means that the physical properties of signal depend on time variation and the instantaneous frequency represents physical property of these type of signal. Thus estimation of the instantaneous frequency of non-stationary signal is important subject in signal processing. In this work, the instantaneous frequency analysis method utilizing continuous wavelets transform is represented and compared with Hilbert Transform method.

• Journal of Internet Computing and Services
• /
• v.4 no.3
• /
• pp.9-14
• /
• 2003

The method of vocal tract normalization is a successful method for improving the accuracy of inter-speaker normalization. In this paper, we present an intra-speaker warping factor estimation based on pitch alteration utterance. The feature space distributions of untransformed speech from the pitch alteration utterance of intra-speaker would vary due to the acoustic differences of speech produced by glottis and vocal tract. The variation of utterance is two types: frequency and amplitude variation. The vocal tract normalization is frequency normalization among inter-speaker normalization methods. Therefore, we have to consider amplitude variation, and it may be possible to determine the amplitude warping factor by calculating the inverse ratio of input to reference pitch. k, the recognition results, the error rate is reduced from 0.4% to 2.3% for digit and word decoding.

• Speech Sciences
• /
• v.4 no.2
• /
• pp.115-139
• /
• 1998

The aim of this study is to develop an the assessment program for the singing voice which is based on the physiological and acoustic methods. 22 sopranos, 6 mezzo sopranos, 4 tenors and 4 baritones participated to these experiments. The results measured by Visi-Pitch, spectrograph, and strobo-scope can be summarized as follows: (1) The maximum phonation time of singers must over 14 second higher with one deep inspiration (2) The parts classified by vocal range using Visi-Pitch: soprano between 167Hz $\sim$1,190Hz, mezzo soprano between 146Hz$\sim$956Hz, tenor between 75Hz$\sim$503Hz and baritone between 73 Hz and 385 Hz. (3) Longitudinal glottal size of singers decreases depending on the high-low pitch variation while lattitudinal glottal size increases depending on high-low pitch variation. (4) Well-trained singers show over 5 times the vibrato rate of untrained singers and regular pitch variation during measured periods. Vibrato's intensity do not over 3 dB. (5) Singer's formant indicates professional voice depending on the each parts: 3,207 Hz for soprano, 3,057 Hz for mezzo soprano, 2,754 Hz for tenor and 2,560 Hz for baritone.. (6) $F_1$ of singing voice is higher than that of speech while $F_2\;and\;F_3$ of singing voice are lower than those of speech.

• The Journal of the Acoustical Society of Korea
• /
• v.24 no.8
• /
• pp.469-480
• /
• 2005

There have been always some difficulties in target setting and conditioning of acoustic performances or the Korean traditional music hall due mainly to the lack of the information on the sound radiation characteristics of Korean musical sources. As the 2nd experiment succeeding the previous study[1], the radiation characteristics of eight typical Korean traditional musical sources were investigated if precision. The selected musical sources were Geomungo, Haegeum (string), Piri, Taepyeongso (woodwind), Buk, Kwaengguari, Jing (drum), and male Pansori Chang (vocal Performance). The results show that the directivity pattern of each instrument is different and has their own directivity characteristics. Measured directional and spectral characteristics of traditional Korean music sources were implemented into the computation of architectural acoustic measures. Significant differences in the acoustic measures at receiver positions were observed between the results in using the omni-directional source and the directional one. In order to investigate the acoustical characteristics of the instruments depending on the spatial variation four different shapes of halls were introduced including rectangular, fan. horse-shoe and geometrical shapes. Room acoustical parameters such as RT, SPL, C80, LF, STI were calculated at each type or hall. As the results, It was found that the rectangular hall has the most high clarity. lateral energy and STI values among low shapes of halls. It is thought that the suggested source data and design method can be used as a basic reference in the future acoustic design of performance halls for the Korean traditional music.

• The Journal of the Acoustical Society of Korea
• /
• v.39 no.2
• /
• pp.77-86
• /
• 2020

In this study, the Eulerian/Lagrangian one-way coupling method is proposed to predict flow noise due to Blade-Tip Vortex Cavitation (BTVC). The proposed method consists of four sequential steps: flow field simulation using Computational Fluid Dynamics (CFD) techniques, reconstruction of wing-tip vortex using vortex model, generation of BTVC using bubble dynamics model and acoustic wave prediction using the acoustic analogy. Because the CFD prediction of tip vortex structure generally suffers from severe under-prediction of its strength along the steamwise direction due to the intrinsic numerical damping of CFD schemes and excessive turbulence intensity, the wing-tip vortex along the freestream direction is regenerated by using the vortex modeling. Then, the bubble dynamics model based on the Rayleigh-Plesset equation was employed to simulate the generation and variation of BTVC. Finally, the flow noise due to BTVC is predicted by modeling each of spherical bubbles as a monople source whose strength is proportional to the rate of time-variation of bubble volume. The validity of the proposed numerical methods is confirmed by comparing the predicted results with the measured data.

• Proceedings of KOSOMES biannual meeting
• /
• 2007.11a
• /
• pp.9-14
• /
• 2007

To illusσ'ate the variation of current around artificial upwelling structure which is located in the South sea of Korea, current measurements using ADCP (Acoustic Doppler Current Profiler) during neap and spring tides were carried out on 27th July(summer)， 14th October and 30th November(Autumn), 2006. Current after the set up of artificial upwelling structure were shown different in the upper and lower layer, the boundary between the upper and lower layer was at $27{\sim}30m$ depth in summer. And the boundary layer was formed structure of three layer in Autumn. Upwelling and downwelling flow were occurred around the seamount， and these vertical flows were connected from surface to bottom The distribution of vertical shear and relative vorticity support the vertical flow around the seamount. The strength of vertical shear was higher and the direction of relative vorticity was anticlockwise (+) around the upwelling area.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.8
• /
• pp.24-30
• /
• 2001

This article is concerned with automatic segmentation for Korean speech signals. All kinds of transition cases of phonetic units are classified into 3 types and different strategies for each type are applied. The type 1 is the discrimination of silence, voiced-speech and unvoiced-speech. The histogram analysis of each indicators which consists of wavelet coefficients and SVF (Spectral Variation Function) in wavelet coefficients are used for type 1 segmentation. The type 2 is the discrimination of adjacent vowels. The vowel transition cases can be characterized by spectrogram. Given phonetic transcription and transition pattern spectrogram, the speech signal, having consecutive vowels, are automatically segmented by the template matching. The type 3 is the discrimination of vowel and voiced-consonants. The smoothed short-time RMS energy of Wavelet low pass component and SVF in cepstral coefficients are adopted for type 3 segmentation. The experiment is performed for 342 words utterance set. The speech data are gathered from 6 speakers. The result shows the validity of the method.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.2E
• /
• pp.57-64
• /
• 1995

In this study, we examine the applicability of the classifier based on an artifical neural network (ANN) for the low-frequency acoustic signal in shallow water environment. The estimations of the Doppler shift and frequency spreading effect at 220 Hz reveal the frequency variation of less than 2 Hz with time This small variation enables the ANN-based classifier to identify signals using only tonal frequency information. The ANN consists of 4 layers, and has 60 input processing elements (PEs) and 4 output PEs, respectively. When measured tonal signals in the frequency 200-250 Hz are applied to the ANN-based classifier, the classifier can identify more than 67% of the signals for instantaneous frame and more than 91% for averaged one over 5 frames.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.38 no.3
• /
• pp.47-54
• /
• 2001

This study is to analyze the impedance response in human body by acoustic stimulation on acupoints and contrast parte; for objectification of the meridian substance. It is to verify meridian pathway and channel theory or bio-energy in body. This paper proposes to make an hypothesis about the underground water theory. The meridian has not tube or pipe line type channel but bio-energy flow along the channel similar to flowing pattern of underground water in body. It was analyzed the current characteristic or impedance response after acoustic stimulation by sound wave of 5 specific tones. The response characteristics of current stimulation are measured by the average current magnitude and variation ratio or meridian. The current variation ratio or Live Meridian(gung) 33.2%, Heart Meridian(sang) 30.7% Kidney Meridian (gak) 33.1%, Spleen Meridian(chi) 33.9%, Lung Meridian (wo) 30.7% are to be compared to contrast parts (non-acupoint and meridian). In experimental results, meridian is discrimination to non-meridian, and 5 vital meridians have a reciprocal relationship with sound wave of 5 specific tones.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.8
• /
• pp.1818-1826
• /
• 2014

Time-variant sea surface causes a forward scattering and Doppler spreading in received signal on underwater acoustic communication system. This results in time-varying amplitude, frequency and phase variation of the received signal. In such a way the channel coherence bandwidth and fading feature also change with time. Consequently, the system performance is degraded and high-speed coherent digital communication is disrupted. In this paper, quadrature phase shift keying (QPSK) performance is examined in two different sea surface conditions. The impact of sea surface scattering on performance is analyzed on basis of the channel impulse response and temporal coherence using linear frequency modulation (LFM) signal. The impulse response and the temporal coherence of the rough sea surface condition were more unstable and less than that of the calm sea surface condition, respectively. By relating these with time variant envelope, amplitude and phase of received signal, it was found that the bit error rate (BER) of QPSK are closely related to time variation of sea surface state.