• Phonetics and Speech Sciences
• /
• v.11 no.3
• /
• pp.9-21
• /
• 2019

This study aimed to compare the prosodic characteristics of North Korean defectors and South Koreans in three types of sentences (declarative, interrogative, and negative) in two reading tasks (short and dialogue) through acoustic analysis and auditory-perceptual evaluation. In addition, this study examined the relationship between the auditory-perceptual evaluation scores and self-assessment questionnaires on intonation for North Korean defectors. The participants were 15 North Korean defectors and 15 Korean speakers with standard Seoul accents. For statistical analysis, three-way mixed ANOVA and multivariate analysis were performed within the three types of sentences in the reading tasks through acoustic analysis and the Mann-Whitney U Test for auditory-perceptual evaluation. Pearson's product-moment correlation coefficients were also used to identify the correlations between the results of the self-assessment questionnaire on intonation and the auditory-perceptual evaluation. The North Korean defectors were found to have a significantly lower pitch range and auditory-perceptual evaluation score than South Koreans in reading tasks. Moreover, there was a significant correlation between their auditory-perceptual evaluations and self-assessment questionnaires on intonation. The study findings suggest that North Korean defectors, who face many challenges with intonation, showed a tendency to think that their intonation differed from the standard Korean intonation and showed better auditory evaluation results for interrogative sentences.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.6
• /
• pp.291-297
• /
• 2006

This paper proposes a new Digital Reverberator that models Analog Helical Coil Spring Reverberator for guitar amplifiers. While the conventional digital reverberators are proposed to provide better sound field mainly based on room acoustics, no algorithm or analysis of digital reverberators those model Helical Coil Spring Reverberator was proposed. Considering the fact that approximately $70{\sim}80$ percent of guitar amplifiers are still with Helical Coil Spring Reverberator, research was performed based not on Room Acoustics but on Helical Coil Spring Reverberator itself as an effector. After performing simulations with proposed algorithm, it was confirmed that the Digital Reverberator by proposed algorithm provides perceptually equivalent response to the conventional Analog Helical Coil Spring Reverberators.

• The Journal of the Acoustical Society of Korea
• /
• v.33 no.6
• /
• pp.358-365
• /
• 2014

When a ship propeller having wing type sections rotates at high speed underwater, local pressure on the blade decreases and various types of the cavitation inevitably occur where the local pressure falls below the vapor pressure. Fundamentally characteristics of the cavitation are determined by the shapes of the blade section and their operating conditions. Underwater noise radiated from a ship propeller is directly connected to the occurrence of the cavitation. In order to design low noise propeller, it is preferentially demanded to figure out key features: how the cavity is generated, developed and collapsed and how the effect of viscosity works in the process. In this study, we first perform inviscid analysis of the partial cavity generated on two dimensional hydrofoil. Secondly, viscous analysis using FLUENT with different turbulence and cavitation models are presented. Results from both approaches are also compared and estimated.

• The Journal of the Acoustical Society of Korea
• /
• v.16 no.2
• /
• pp.31-35
• /
• 1997

In this paper, we propose a variable vocabulary word recognizer that is able to recognize new words not exist in training data. For the variable vocabulary word recognizer, we must have an on-line lexicon generator to transform new candidate words to the corresponding pronunciation sequences of phones without any large lexicon table. And, we also must make outputs. In order to model the phones and allophones reliably, we define Korean allophones by triphone clustering based on phonetic knowledge of preceding and succeeding phones of each phone. Using the clustering method, we generated 1,548 allophones with POW (Phonetically Optimized Words) 3,848 word DB. We evaluated the proposed word recognizer with POW 3,848 DB, PBW (Phonetically Balanced Words) 445 DB, and 244 word DB in hotel reservation task. Experimental results showed word recognition accuracy of 79.6% for the POW DB corresponding to vocabulary-dependent case, 79.4% in case of 445 word lexicon and 88.9% in case of 100 word lexicon for the PBW DB, and 71.4% for the hotel reservation DB corresponding to vocabulary-independent case.

• The Journal of the Acoustical Society of Korea
• /
• v.26 no.7
• /
• pp.361-365
• /
• 2007

Aero-pulsation noise, generally caused by geometric asymmetry of a rotating device, is one of considerable sources of annoyance in passenger cars using the turbocharged diesel engine. Main source of this noise is the compressor wheel in the turbocharger system, and can be reduced by after-treatment devices such as silencers, but which may increase the manufacturing cost. More effective solution is to improve the geometric symmetry over all, or to control the quality of components by sorting out inferior ones. The latter is more simple and reasonable than the former in view of manufacturing. Thus, an appropriate discrimination method should be needed to evaluate aero-pulsation noise level at the production line. In this paper, we introduce the accurate method which can measure the noise level of aero-pulsation and also present its evaluation criteria. Besides verifying the reliability of a measurement system - a rig test system-, we analyze the correlation between the results from rig tests and those from vehicle tests. The gage R&R method is carried out to check the repeatability of measurements over 25 samples. From the result, we propose the standard specification which can discriminate inferior products from superior ones on the basis of aero-pulsation noise level.

• Phonetics and Speech Sciences
• /
• v.13 no.2
• /
• pp.91-101
• /
• 2021

The purpose of this study was to investigate laryngeal characteristics in children with autism spectrum disorders (ASD). A total of 50 children participated, including eight children aged 2 to 4 years old diagnosed with ASD and 42 normal controls at the same age. All children recorded X-ray images of the midsagittal plane of the cervical spine and larynx, and compared the laryngeal positions of ASD and control. In addition, samples of children with vowel prolongation were collected and analyzed for acoustic parameters. X-rays showed that the height of the hyoid bone in the normal group was the lowest at 3 years of age, and ascended at 4 years of age. Nevertheless, the distance from the external acoustic meatus to the hyoid bone was longest at age 4. 4-year-olds with explosive language development showed laryngeal height elevation and anteriorization. In contrast, the hyoid height of the ASD group of all ages was lower than that of the control group, and there was no difference in the hyoid position between the ages. As a result of acoustic evaluation, PFR, vFo, and vAm were significantly higher ASD than control. Low laryngeal height of ASD children may be associated with delayed language development. PFR, vFo, and vAm seem to be voice markers showing the difference between normal and ASD children.

• Clinical and Experimental Pediatrics
• /
• v.53 no.4
• /
• pp.579-584
• /
• 2010

Purpose : The number of the repatriated Korean students who had overseas study at early ages is increasing. They received foreign education, they can speak international languages, but they have many difficulties in articulation and intonation of the Korean language. This study aims to measure closure and aspiration duration, length of consonants, length of subsequent vowels, and ratio of consonants against subsequent vowels in vowel-consonant-vowel (VCV) syllables. Methods : This study compares the acoustic and phonetic characteristics of repatriated and native students, the ratio of articulation error of Korean plosives, the closure and aspiration duration, and the ratio of the aspiration duration against the closure duration. Results : The ratio of articulation error of Korean plosives between repatriated and native students is 19% and 2%, respectively. The closure duration was significantly longer in repatriated students than in native students. The aspiration duration was significantly longer in repatriated students than in native students. No difference was found in the ratio of aspiration duration against closure duration between the native and repatriated students. Conclusion : This study can be a good reference for estimating the phonetic difficulties of Korean elementary students who had overseas study at early ages.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.2
• /
• pp.63-72
• /
• 2011

Since the detection probability is critically dependent on the target strength (TS) in active sonar and on the radiated noise level (RNL) in passive sonar, the acoustic materials for echo reduction (ER) and transmission loss (TL) are widely used for the stealth of underwater targets. In this paper, a measurement system based on the small water tank, for the frequency range of greater than 30 kHz, is developed and verified using reference targets. In order to design the water tank and the geometry of test samples, a program is developed to calculate the arrival time of interfering signals due to the reflection from water tank walls and also due to the diffraction from the edge of the test samples. Considering all the interfering signals, an optimal experimental configuration for water tank and test samples is designed and used throughout the experiment. Next, the signal processing algorithms to estimate ER and TL are developed based on the measured propagation loss reflecting the geometric spreading characteristics of the transducer. Finally, a set of reference targets such as aluminium plate and perfectly reflecting plate are used in a small water tank to verify the developed measurement system.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.4
• /
• pp.342-348
• /
• 2003

Ultrasonic backscattering profiles of the Zr plates(with a thickness of 1.32mm) with/without Be-Zr alloy layer(with a thickness of $100{\mu}m$) were measured at various incidence positions to evaluate the characteristics of Be diffusion layer. Four principal subprofiles were observed in the backward ultrasound radiated from leaky Lamb waves. The angles and the intensities of the subprofile peaks decreased by the stiffening effect of Be layer. Generation and change of the subprofiles were explained by the acoustical property, collective group velocity and leaky factor difference of the plates under consideration. Backward radiation subprofiles turned out to be an useful method for evaluating thin diffusion layers on plates.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.105-108
• /
• 1999

TTS(Text-To-Speech) 시스템 합성음성의 자연감을 개선하기 위해 하나의 언어에 대해 존재하는 운율 법칙을 정확히 구현해야 한다. 존재하는 운율 법칙을 추출하기 위해서는 방대한 분량의 언어 자료 구축이 필요하다. 그러나 이 방법은 존재하는 운율 현상이 포함된 언어자료에 대해 완벽한 운율을 파악할 수 없으므로 합성음성의 질을 좋게 할 수 없다. 본 논문은 한국어 음성의 운율을 학습하기 위해 2개의 인공 신경망을 제안한다. 하나의 신경망으로 문장의 각 음소에 대한 피치 변화를 학습시키는 것이며, 다른 하나는 에너지 변화를 학습하도록 하였다. 신경망은 BP 신경망을 이용하며 11개의 음소를 나타내기 위해 11개의 입력과, 중간 음소의 피치와 에너지 변화곡선을 근사하는 다항식 계수를 출력하도록 하였다. 신경망시스템의 학습과 평가에 앞서, 음성학적 균형잡힌 고립단어를 기반으로 의미있는 문장을 구성하였다. 문장을 남자 화자로 하여금 읽게 하고 녹음하여 음성 DB를 구축하였다. 음성 DB에 대해 각 음소의 운율 정보를 수집하여 신경망에 맞는 목표 패턴과 훈련 패턴을 작성하였다. 이 목표 패턴은 회귀분석을 통한 추세선을 이용해 피치와 에너지에 대한 2차 다항식계수로 구성하였다. 본 논문은 목표패턴에 맞는 신경망을 학습시켜 좋은 결과를 얻었다.