• The Journal of the Acoustical Society of Korea
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• v.41 no.1
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• pp.58-63
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• 2022

This study was conducted to examine the characteristics of pitch perception and temporal resolution through Within-/Cross-Channel Gap Detection Thresholds (WC/CC GDTs) using low-frequency pure tones (such as 264 Hz, 373 Hz and 528 Hz related to C4, C4#, and C5 musical tones. 40 young people and 20 elderly people with normal hearing participated in this study. The results of WC GDTs were approximately 2 ms ~ 4 ms threshold values regardless of frequencies in two groups. There was no statistically significant difference in WC GDTs between groups. In both groups, CC GDTs were larger than WC GDTs, and as the frequency difference increased, the CC GDTs also increased. In particular, in the comparison between groups of CC GDTs, the results of the elderly group were 8 times ~ 10 times larger than that of the young group, and there was a statistically significant difference between the groups. These data also showed a different trend of GDTs in comparison with the previous data obtained from musical stimuli.This study suggests that GDTs may influence pitch perception mechanisms and can be used as psychoacoustic evidence for nonlinear responses of auditory nervous system.

• Smart Media Journal
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• v.12 no.2
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• pp.56-65
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• 2023

In broadcasts such as news and coverage programs, voice is modulated to protect the identity of the informant. Adjusting the pitch is commonly used voice modulation method, which allows easy voice restoration to the original voice by adjusting the pitch. Therefore, since broadcast voice modulation methods cannot properly protect the identity of the speaker and are vulnerable to security, a new voice modulation method is needed to replace them. In this paper, using the Lightweight speech de-identification model as the evaluation target model, we compare speech de-identification performance with broadcast voice modulation method using pitch modulation. Among the six modulation methods in the Lightweight speech de-identification model, we experimented on the de-identification performance of Korean speech as a human test and EER(Equal Error Rate) test compared with broadcast voice modulation using three modulation methods: McAdams, Resampling, and Vocal Tract Length Normalization(VTLN). Experimental results show VTLN modulation methods performed higher de-identification performance in both human tests and EER tests. As a result, the modulation methods of the Lightweight model for Korean speech has sufficient de-identification performance and will be able to replace the security-weak broadcast voice modulation.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.54-62
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• 2023

Flapping-wing air vehicles, well known for their free vertical take-off and excellent flight capability, are currently under intensive development and research. While most of the studies have explored the effect of various parameters of synchronized motions on the unsteady aerodynamics of flapping wings, limited attention has been given to the effect of nonsynchronous motions on the unsteady aerodynamic characteristics of flapping wings. In the present study, we conducted a numerical analysis to investigate the unsteady aerodynamic characteristics of an airfoil flapping with different frequency ratios between pitch and heave oscillations. We identified the motions and angle of attacks due to nonsynchronous motions. It was found that the synchronous motion produced thrust with zero lift, but the nonsynchronous motion generated a large lift with little drag. The aerodynamic characteristics of the airfoil undergoing the non-synchronous motion were also analyzed using the vorticity distributions and the pressure coefficient around and on the airfoil. When r was equal to 0.5, larger leading and trailing edge vortices were observed compared to the case when r was equal to 1.0, and these vortices significantly affected the aerodynamic characteristics of the airfoil undergoing the nonsynchronous motion. In future, the effect of pitch amplitude on the unsteady aerodynamic characteristics of the airfoil will be studied.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.259-262
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• 1993

In this paper, a new pitch beginning point detection method by extracting the G-peak, is proposed. By the speech production model, the area of the first peak on a pitch interval of speech signals is emphasized. By using the above characteristics, this method have more advantages than the others for pitch beginning point detection. The defective decision caused by an impulsive noise is minimized and the pre-filtering is not necessary for this method, because the integration of signals takes place in the process.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.88-92
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• 1993

In speech signal processing, it is necessary to detect exactly the pitch. The algorithms of pitch extraction which have been proposed until now are difficult to detect pitches over wide range speech signals. Thus we propose a new algorithm which uses the G-peak extraction to do it. It is the method that finds the most MZI(maximum zero-crossing interval) at each frame and convolve it with speech signal ; this is the same with passing speech signals to variable LPF. Finally we obtained the pitch, improve the accuracy of pitch detection and extract it with the high speed.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.227-230
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• 2001

반향(Echo)을 이용한 워터마킹은 오디오 신호에 인위적인 반향을 첨가함으로써 정보를 삽입한다. 다른 오디오 워터마킹 방법과 마찬가지로 반향 오디오 워터마킹은 시간축 공격에 대해 강인하지 못한 단점을 가지고 있다. 특히, 오디오 신호의 피치를 보존하면서 재생 시간을 변형시키는 시간 스케일 변형 (Time Scale Modification)에 대해서는 별도의 방어를 위한 알고리듬이 없을 경우 전혀 복호화가 이뤄지지 않는다. 본 논문에서는 반향 오디오 워터마킹의 성능 향상을 위해 시간 스케일 변형 공격에 대응하여, 변형된 정도를 검출하고 보상하여 복호화가 가능하도록 하는 새로운 알고리듬을 제안한다.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.797-800
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• 2001

스펙트럼의 평탄화는 스펙트럼 신호로부터 포만트의 영향이나 천이진폭의 영향을 제거하는 것이다. 따라서 정확한 피치검출과 포만트검출에 적용할 수 있다. 본 논문에서는 새로운 스펙트럼 평탄화 기법을 제안하고 기존의 방법인 LPC법, Cepstrum법과 비교하여 어느 정도의 우수성을 보이는지 평가하였다. 평가 방법은 각각의 평탄화된 신호의 분산을 구하여 평탄화의 정도를 측정하였다. 이때 핑탄화된 신호는 최고점이 영이 되도 록 정규화 시키고 평균이 영인 분산을 계산하였다. 실험 결과는 제안한 방법이 기존의 방법보다 우수함을 보여 준다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.123-126
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• 2000

STC(Sinusoidal Transform Coding) 방식은 음성신호의 주파수 영역에서 스펙트럼 피크치들을 정현파로 모델링하여 합성하는 방식을 말한다. 저전송률 STC 방식에서는 전송되는 정보량을 줄이기 위해 스펙트럼 피크를 대신해 음성신호의 스펙트럼 포락선 정보와, 피치정보를 이용하여 얻어지는 고조파 성분들을 정현파로 모델링하여 음성을 합성한다. 본 논문에서는 음성신호의 정현파 모델에 기반하여 2.4kbps 전송속도를 갖는 음성부호화 알고리즘을 제안하였으며, 실험결과로 합성음의 파형과 스펙트럼 특성, 위상특성, 그리고 MOS(Mean Opinion Score) 테스트를 이용한 합성음의 음질을 비교/분석 하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.622-626
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• 1993

비원형기어의 기본적인 특징을 몇 가지 소개하고자 한다. 첫째, 간소한 기구로서 소형화할 수 있고, 둘째, 임의의 부동속 회전 전달을 얻을 수 있으며, 셋째, 맞물린 치면의 미끄럼접촉이 적기 때문에 마모피로가 적고 넷째, 고부하 전달이 가능하다는 장점들이 있다. 본 연구의 목적은 링크, 캠과 같은 동일한 용도에서 사용되는 다른 여러 기구에 비해 많은 이점을 가지고 있는 적합한 타원계 비원형기어(엽형)에서 편평도의 변화에 따른 피치라인을설계하고, 각속비 및 편평도에 따른 형상과 길이의 변화, 물림압력각, 곡률반경등의 연구를 바탕으로 스퍼형과 헬리컬형의 타원계 엽형로타를 AOTOCAD의 script, 3dace를 이용하여 Computer Simulation를 통해 도형화한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1123-1126
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• 2004

Recognizing emotion in speech is required lots of spoken language corpus not only at the different emotional statues, but also in individual languages. In this paper, we focused on the changes speech signals in different emotions. We compared the features of speech information like formant and pitch according to the 4 emotions (normal, happiness, sadness, anger). In Korean, pitch data on monophthongs changed in each emotion. Therefore we suggested the suitable analysis techniques using these features to recognize emotions in Korean.