• 음성과학
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• 제8권3호
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• pp.93-104
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• 2001

The author analyzed acoustic parameters of ten Korean numbers produced by ten male students using Praat. Variations of f0, F1, F2 and F3 within and between speakers were examined by determining an average and standard deviation of the parameters of each number and by comparing the acoustic values with one another. Results showed that each subject produced the numbers within a certain range of variation across time. Thus, speaker identification can be more certain using dynamic information of the acoustic parameters within each vocalic segment. Also, percent difference of within-subjects' variation to that of between-subjects can be utilized to determine which sounds would be better stimuli for speaker identification. According to the criteria, the number '2' proved the best stimulus while the number '7' was the worst. Future studies will be necessary to explore robust methods of speaker identification under noisy conditions.

• 항공우주기술
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• 제2권2호
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• pp.66-75
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• 2003

우주비행체 음향 환경 시험을 위한 고음압 잔향실이 한국항공우주연구원에서 개발되었다. 우주비행체는 우주로 발사되는 동안 발사체에서 발생되는 고음압의 음향환경에 노출되므로, 발사 이전에 음향 환경에 대한 신뢰성시험이 수행된다. 한국항공우주연구원에 개발된 음향챔버는 부피 1,228세제곱 미터이며, 152dB의 음압을 잔향실 내부에 재생한다. 재생 주파수 범위는 25Hz~10,000Hz이다. 음향 환경 시험시설은 잔향실을 비롯해서, 질소 공급장치, 음원, 스펙트럼 제어시스템 등으로 구성된다. 본 논문은 시험시설을 구성하는 각 요소를 설계하기 위한 기본 개념을 서술한다. 또한 실제 건설된 음향챔버에서 측정된 결과를 바탕으로 음향챔버의 성능을 검증한다.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.5-12
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• 2016

This paper describes the development process for vibration and acoustic characteristics of a balanced armature speaker. The design parameters were chosen in consideration of the influence of the bending stiffness of balanced armature which is the form of a cantilever structure in the speaker. For study of the performance of the speaker according to the design parameters, in the first step, we analyzed the characteristics of the velocity of the diaphragm to the electrical input. Next step, acoustic characteristics were analyzed by structural-acoustic coupled analysis. And the reliability of the analysis was verified by comparing the result of analysis with test results. Finally, we proposed a design method for implementing an enhanced balanced armature speakers through analysis method.

• 말소리와 음성과학
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• 제1권3호
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• pp.117-122
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• 2009

A variety of cross-linguistic studies has documented that the acoustic properties of speech addressed to young children include exaggeration of pitch contours and acoustically salient features of phonetic units. It has been suggested that phonetic modifications of child-directed speech facilitate young children's learning of speech sounds by providing detailed phonetic information about the target word. While there are several studies reporting vowel modifications in speech to infants (i.e., hyper-articulated vowels), there has been little research about consonant modifications in speech to young children (except for VOT). The present study examines acoustic properties of Korean stops in Korean mothers' speech to their children (seven children aged 27 to 38 months). Korean tense, lax, and aspirated stops are all voiceless in word-initial position, and are perceptually differentiated by several acoustic parameters including VOT, $f_0$ of the following vowel, and the amplitude difference of the first and second harmonics at the voice onset of the following vowel. This study compares values of these parameters in Korean child-directed speech to those in adult-directed speech from same speakers. Conclusions focus on the acoustic properties of Korean stops in child-directed speech and how they are modified to help Korean young children learn the three-way phonetic contrast.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.254-257
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• 2010

본 연구에서는 로켓엔진 연소기의 음향 불안정 억제를 위해 헬름홀츠 공명기의 음향학적 최적 설계 조건을 해석/실험적으로 연구하였다. 질량-스프링-댐퍼 시스템과의 유사성을 이용한 모델 식의 풀이를 통해 감쇠 성능을 정량화하였다. 헬름홀츠 공명기의 기하학적 형상 인자로 목의 길이와 공동의 크기, 목 및 공동의 직경을 선택하였다. 목의 길이가 짧아지고, 공동의 길이가 길어짐에 따라 흡음성능이 증가하고, 목과 공동의 직경비가 증가함에 따라 흡음성능은 감소하였다.

• 한국생산제조학회지
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• 제8권3호
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• pp.66-75
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• 1999

This paper is concerned with a analysis of noise by inverse problem available for analyzing the two and three-dimensional acoustic field problems. The noise of analysis considered in this study can be reduced to an optimum problem to find the optimal set of parameters defining the vibrating state of noise source surfaces. The optimal set of parameters are searched by the standard optimization procedure minimizing the square sum of the residuals between the measured and computed quantities of sound pressure at some points in the acoustic field. Computation is carried out for typical examples in which the noise sources are located on the infinite plane. It is demonstrated that the noise of analysis can be effectively made by using the sensitive reference data.

• 음성과학
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• 제9권4호
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• pp.27-38
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• 2002

The purpose of this article is to present the acoustic parameters (VOT, jitter, shimmer, vF0, vAm, NHR, SPI, VTI, DVB, DSH) for consonants (/pipi/, /$p^{h}ip^{h}i$/, /p'ip'i/) and sustained vowels (/a/, /e/, /i/) produced by normal subjects and dysphonia patients at two vocal effort(normal, high) by Lombard effect using 60dB white noise. Lombard effect indicates the vocal effort increase in noisy situation. At normal vocal effort, in general the acoustic parameter values of patients are greater than normal. And in noisy situation, significant decrease of acoustic values is seen in normal compared with in dysphonia patients. The clinical implication of this finding, the vocal quality in dysphonia is not compensated by vocal effort as well as normal subjects because of the inefficiency caused by abnormal vocal fold appearance and function. And with this result, we can counsel that the voice quality can not be improved as well as the patient expect.

• 대한후두음성언어의학회지
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• 제6권1호
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• pp.22-26
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• 1995

Change of voice, espicially hoarseness show irregular vibration of vocal cord. So, computerized acoustic analysis has presented many acoustic parameters for objective evaluation of voice. We objectively investigated the vocal vibration of normal persons and hoarseness patients in Korea. The RAP(relative average perturbation), PPQ(pitch period perturbation quotient) and APQ(amplitude perturbation quotient) of normal persons were compared with that of hoarseness patients with multidimensional voice program for the possibility of distinguishing the pathologic vocal vibration from normal. Authors agree that RAP, PPQ and APQ showed interesting differences between the normal and the hoarseness patients by the multivariate statistical analysis. In conculusion, relative average perturbation, pitch period perturbation and amplitude perturbation quotient might be meangingful screening parameters distinguishing hoarseness patients from normal.

• 오토저널
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• 제14권1호
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• pp.25-37
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• 1992

Interior noise in a car is known to have an important influence on product acceptability. This noise is closely correlated with structural-acoustic vibration. When considering noise problem, the structural-acoustic relation of a vehicle cabin model needs to be identified. However, it is very difficult to get the modal parameters of this kind of cabin structure composed of thin plates: because it not only can be excited by the acoustic vibration of cavity, but also tends to have decoupling effects of one plate from another. In order to obtain modal parameters more precisely, various excitation techniques, i.e. impact, pure random, burst random, and swept sine testing are applied for the first step. In the case of the cabin model, impact and swept sine testing show good results. Next, the determination of the excitation point by trial- and-error and the accurate measurements of FRF's are performed with these methods. The modal parameter extraction is carried out for the final step. This paper proposes a new approach to find the modal parameters more reliably in the case of high decoupling effects. That is, the convergence of MIF and MCF in each panel, which provide some criteria for the validity of the obtained modal parameters, is observed. And from those results, the pretty accurate modal parameters can be determined. A comparative assessment between the modal testing and the FEM is also performed.

• 방사성폐기물학회지
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• 제19권1호
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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.