• Phonetics and Speech Sciences
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• v.1 no.3
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• pp.19-28
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• 2009

This paper reports experimental findings about the duration feature of the acoustic components of English stops in Korean speakers' voicing perception. In our experiment, 35 participants discriminated between recorded stimuli and digitally transformed stimuli with different duration features from the original stimuli. 72 sets of paired stimuli are generated to test the effects of the duration feature in various phonetic contexts. The result of our experiment is a complicated cross-tabulation with 540 cells defined by five categorical independent variables plus one response variable. To find a meaningful generalization out of this complex frequency table, we ran logit log-linear regression analyses. Surprisingly, we have found that there is no single effect of the duration feature in all phonetic contexts on Korean speakers' perception of the voicing contrasts of English stops. Instead, the logit log-linear analyses reveal that there are interaction effects among phonetic contexts (=C), the places of articulation of stops (=P), and the voicing contrast (=V), and among duration (=T), phonetic contexts, and the places of articulation. To put it in mathematical terms, the distribution of the data can be explained by a simple log-linear equation, logF=${\mu}+{\lambda}CPV+{\lambda}TCP$.

• Phonetics and Speech Sciences
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• v.3 no.1
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• pp.23-34
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• 2011

Many Korean children have difficulty learning English vowels. The gestures inside the oral and pharyngeal cavities are hard to control when they cannot see the gestures and the target vowel system is quite different from that of Korean. This study attempts to collect children's acoustic data of twelve English vowels published by Hillenbrand et al. (1995) online and to examine the acoustic features of English vowels for phoneticians and English teachers. The author used Praat to obtain the data systematically at six equidistant timepoints over the vowel segment avoiding any obvious errors. Results show inherent acoustic properties for vowels from the children's distribution of vowel duration, f0 and intensity values. Second, children's gestures for each vowel coincide with the regression analysis of all formant values at different timepoints regardless of the vocal fold and tract difference. Third, locus points appear higher than those of American males and females. Their gestures along the timepoints display almost similar patterns. From the results the author concludes that vowel formant trajectories provide useful and important information on dynamic articulatory gestures, which may be applicable to Korean children's education and correction of English vowels. Further studies on the developmental study of vowel formants and pitch values are desirable.

• ETRI Journal
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• v.41 no.2
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• pp.235-241
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• 2019

In this paper, we propose a rank-weighted reconstruction feature to improve the robustness of a feed-forward deep neural network (FFDNN)-based acoustic model. In the FFDNN-based acoustic model, an input feature is constructed by vectorizing a submatrix that is created by slicing the feature vectors of frames within a context window. In this type of feature construction, the appropriate context window size is important because it determines the amount of trivial or discriminative information, such as redundancy, or temporal context of the input features. However, we ascertained whether a single parameter is sufficiently able to control the quantity of information. Therefore, we investigated the input feature construction from the perspectives of rank and nullity, and proposed a rank-weighted reconstruction feature herein, that allows for the retention of speech information components and the reduction in trivial components. The proposed method was evaluated in the TIMIT phone recognition and Wall Street Journal (WSJ) domains. The proposed method reduced the phone error rate of the TIMIT domain from 18.4% to 18.0%, and the word error rate of the WSJ domain from 4.70% to 4.43%.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.1
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• pp.75-85
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• 2021

Evaluating the quantitative damage to rocks through acoustic emission (AE) has become a research focus. Most studies mainly used one or two AE parameters to evaluate the degree of damage, but several AE parameters have been rarely used. In this study, several data-driven models were employed to reflect the combined features of AE parameters. Through uniaxial compression tests, we obtained mechanical and AE-signal data for five granite specimens. The maximum amplitude, hits, counts, rise time, absolute energy, and initiation frequency expressed as the cumulative value were selected as input parameters. The result showed that gradient boosting (GB) was the best model among the support vector regression methods. When GB was applied to the testing data, the root-mean-square error and R between the predicted and actual values were 0.96 and 0.077, respectively. A parameter analysis was performed to capture the parameter significance. The result showed that cumulative absolute energy was the main parameter for damage prediction. Thus, AE has practical applicability in predicting rock damage without conducting mechanical tests. Based on the results, this study will be useful for monitoring the near-field rock mass of nuclear waste repository.

• Journal of Apiculture
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• v.34 no.1
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• pp.7-13
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• 2019

Vespid wasps (Vespa spp.) are the most noxious pests on apiculture, resulting in significant economic losses. Early monitoring and management are the first step to prevent the damages from vespid wasps. In this study, the acoustic signals from wasps and honey bees were measured by a microphone with a preamplifier and an analog-digital converter. In frequency analysis of the acoustic signals from wasps and honey bees, there were differences between the two species. While the fundamental frequency of the wasps was analyzed to be about 100 Hz with the strong harmonic frequencies, that of the honey bees was about 200~250 Hz. The 2nd harmonic signals from wasp were strongest while the fundamental ones from honey bees were. These different sound features generated by wasps or honey bees might be applied to develop the early monitoring system of the incursion of wasps to the apiary.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.25 no.1
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• pp.20-23
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• 2014

Age-related changes in larynx can have a direct impact on voice quality and general comfort level. Observations of vocal aging have spanned perceptual, acoustic, aerodynamic, physical, electromyographic (EMG) and histological levels. Evidence of differential vocal aging in relation to gender and physical condition has been reported. Perceptual, acoustic, aerodynamic, kinematic, EMG and histological data document age-related changes in laryngeal structure and function with advancing age. These changes contribute to a functional age-related impact of vocal hypofunction or compensatory hyperfunction. This review will focus on the current understanding of the clinical and cellular changes in the larynx that lead to presbyphonia.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.37-43
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• 2005

Real time monitoring of exit burr formation is critical in manufacturing automation. In this paper, acoustic emission (AE) was used to detect the burr formation during drilling. By using wavelet transform (WT), AE data were compressed without unnecessary details. Then the transformed data were used as selected features (inputs) of a back-propagation artificial neural net (ANN). In order to validate the in process AE monitoring system, both WT-based ANN and cutting condition (cutting speed, feed, drill diameter, etc.) based ANN outputs were compared with experimental data.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.49-51
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• 2004

This paper presents a realization of fault detection algorithm and Fieldbus based communication for condition monitoring of check valve. We first acquired the AE(Acoustic Emission) sensor data at the KAERI check valve test loop, extract fault features through the learned Neural network, and send the processed data to a remote site. The overall system has been implemented and experimental results are given to show its effectiveness.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.60-65
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• 2001

Thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, Stacking of the particles makes coating. In this study, the exfoliation of $Al_2$O$_3$ and Ni-4.5wt.%Al thermally sprayed coating which were deposited by an atmospheric plasma spray apparatus are investigated using an AE method. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. The wave forms of AE generated from the three coating specimens can be classified by FFT analysis into two types which low frequency(type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip or the resultant fracture of coating. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.510-514
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• 2011

To detect the insulator in the fault state on the electric poles, we first measured radiation sounds from normal state insulators and error state insulators in the anechoic chamber. We processed the signals in frequency domain to find the features with filter bank, narrow band and wide band analysis. So we could found two apparent results from their frequency spectrums - one was 120Hz harmonic components, the other was high average noise level than normal state ones. Then we also introduced a technique for the direction detection of the fault state insulator using the cross correlation from the three dimensional array microphones. To eliminate the noise signal from unexpected directions, we suggested the zero padding technique in cross correlation function. From these, we could conclude that acoustic fault detection techniques are useful of the detection of insulators' faults and the estimation of the direction of the fault state insulators.