• Title/Summary/Keyword: noise addition

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Noise reduction based on directional Wiener filter using local adaptive estimation window (가변적인 국부 추정 윈도우를 이용한 방향성 Wiener filter에 의한 잡음 제거)

  • 우동헌;김유신;김재호
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.6A
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    • pp.568-574
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    • 2002
  • The main issue of noise reduction of image is how to preserve edge and reduce noise. Usually, The Wiener falter is used for this purpose. But the conventional Wiener filter cannot remove noise well in both edge and smooth region due to the single size estimation window. In addition, it ignores the correlation between pixels. In this paper, we propose a new noise reduction algorithm, in which adaptive estimation window is used according to property of smooth region and edge region. In order to make edge more clear, directional Gaussian mask and directional estimation window combines to the Wiener filter according to direction of edge. From the simulation results, it can be seen that the proposed algorithm showed improves performance in both PSNR arid subjective evaluation

The Stability and Variability based on Vowels in Voice Quality Analysis (음질 분석에 있어서 모음에 따른 안정성과 변이성)

  • Choi, Seong Hee;Choi, Chul-Hee
    • Phonetics and Speech Sciences
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    • v.7 no.1
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    • pp.79-86
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    • 2015
  • This study explored the vowel effect on acoustic perturbation measures in voice quality analysis. For this study, the perturbation parameters (%jitter, %shimmer) and noise parameter (SNR) were measured with 7 Korean vowels (/a/, /ɛ/, /i/, /o/, /u/, /ɯ/, /ʌ/) using CSpeech with 50 Korean normal young adults (24 males and 26 females). A significant vowel effect was found only in %shimmer and in particular, low-back /a/vowel was significantly different from other vowels in %shimmer. The least perturbation and noise were exhibited on high-back /ɯ/ and /o/ vowel, respectively. Based on tongue height, a significant higher %shimmer was demonstrated on low vowels than high vowels. In addition, back vowels in tongue advancement and rounded vowels in lip rounding showed significantly less perturbation and noise. The least variability of perturbation and noise within individuals was demonstrated on the vowel /i/ in three repeated measures. However, there was no significant difference among 3 token measures in single session among vowels tested except the vowel /o/. Consequently, the vowel /a/ commonly used in acoustic perturbation measures exhibited higher perturbation and noise whereas higher stability and less variability were demonstrated on the high-back vowel /u/. These results suggested that the Korean high-back vowel /u/ can be more appropriate and reliable for perturbation acoustic measures.

Numerical Study on the Control of Heavy-weight Floor Impact Noise for PC Slab Coupled with Viscoelastic Material (점탄성재료가 결합된 PC 슬래브의 중량충격음 저감에 관한 수치해석 연구)

  • Hwang, Jae-Seung;Song, Jin-Kyu;Hong, Geon-Ho;Park, Hong-Gun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.5
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    • pp.533-540
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    • 2008
  • In this study, a new slab system where a part of precast slab is connected each other by viscoelastic material is proposed and numerical analysis is performed to evaluate the effect of the connection between the material and PC slab on the vibration and noise control. Substructuring is introduced to develop the equation of motion for the slab system. In addition, the optimal properties of viscoelastic material are investigated. For the performance evaluation of the new slab system, the sound power and acceleration responses of the slab are compared with those of two way slab and one way slab, respectively. Numerical analysis results show that the sound power of the new slab system can be reduced by viscoelastic material significantly.

The Analysis of Spectrum on the Barkhausen Noise of Hysteresis Loops on Neutron Irradiated Material

  • Sim, Cheul-Muu;Chang, Kee-Ok;Park, Kook-Nam;Cho, Man-Soon;Park, Chang-Oong
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.1E
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    • pp.7-12
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    • 1999
  • In relation to a non-destructive evaluation of irradiation damages, the changes in the hysteresis loop and Barkhausen noise amplitude and the harmonics frequency due to a neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of RPV was irradiated to a neutron fluence of 2.3 ×10/sup 19/ n/㎠ (E ≥1 MeV) at 288℃. The saturation magnetization of neutron irradiated metal did not change. The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by a neutron irradiation. The spectrum of Barkhausen noise is analysed with an applied frequency of 4 Hz and 8 Hz, sampling time of 50 μ sec and 20 μ sec. The harmonic frequency shows 4 Hz, 8 Hz, 12 Hz and 16 Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared on the irradiated specimen. In addition to the amplitude, the harmonic frequency of Barkhausen noise is taken into accounts as a promising tool for monitoring the irradiation induced degradation of the reactor materials such as a SA508 of PWR-RPV steel and a Zr₄ of HANARO-CNH.

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Acoustic Noise Characteristics of Inductor According to Magnetic Powder Core Building Structure for Inverter Application (분말 자성 코어의 형상에 따른 인버터용 인덕터의 소음특성)

  • Yoo, Kwang-Yong;Lee, Byoung-Kuk;Kim, Dong-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.11
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    • pp.1591-1599
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    • 2017
  • In power electronics applications which switching frequency is below audible frequency, the acoustic noise and vibration design of magnetics are as important as the efficiency. In the case of the powder core, which is widely used in grid-connected inverters, many researches have been progressed in terms of efficiency. However, there are only few research have been progressed related with acoustic noise and vibrations. In this paper, the Sendust(Fe-Si-Al) powder core material which has low magnetostriction and low core loss is analyzed in terms of acoustic noise and vibration induced by Maxwell force and magnetostriction. Three building structures such as, rectangular, toroidal, and oval shape are designed for 4kW grid-connected inverter, because magnetic properties and the audible noises of the inductor are varied by magnetic core building structures. The effects of the Maxwell force and magnetostriction behaviors varied with core shapes are analyzed by finite element method and experiments. In addition, experiment results of the inductor efficiency are presented according to core building structures.

Subjective Evaluation of Sound Quality in Vehicle Passenger Compartment during Acceleration (자동차 주행 가속 차실 소음의 주관적 음질 평가)

  • Kang, S.W.;Lee, J.M.
    • Proceedings of the KSME Conference
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    • 2001.06b
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    • pp.187-191
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    • 2001
  • Sound quality engineering in automobile noise applications has become more and more important under the current quiet driving condition that the interior noise level is below 65 dBA, because various noise components masked under high noise level can be audible in quieter driving situation. Many researches have been carried out for subjective and objective assessments on automobile sounds and noises. In particular, the interior sound quality has been one of research fields that can give high-quality feature to automobile products. Although many works related to the interior sound quality have been progressed or completed in foreign countries, limited research results are presented in the country. In the study, as a base step necessary to objective assessments on car interior noises, subjective assessments are performed with 20 subjects. For this purpose, perceptual adjectives suitable to the assessment of acceleration noises are selected as assessment scales through questionnaire procedures using 35 subjects. Mean values and standard deviations are calculated for noises created through digital filtering of acceleration noises measured. In addition, the correlation analysis and the factor analysis are carried out to investigate the dependence of the assessment scales selected.

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A Study on the Design and Chracteristic Analysis for Noise Cut Transformer (NCT 설계 및 특성 분석에 관한 연구)

  • 이재복;허창수
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.12 no.4
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    • pp.146-154
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    • 1998
  • Broadband noise with frequency components in the range from several kHz up the tens of MHz is a major obstacle factor in normal operation of the AC line to supply the power to electrical and electronic control equipments. Because this kind of noise could damage the device or could be a source of malfunction, many devices such as filter and surge suppressor are used to cut off the noise. But those devices could not disconnected from the power line, so they result in poor common-mode of NCT as well as insulation characteristics as a isolation transformer in addition faraday shielding and proposed analysis model of NCT having tow functions of surge and noise reduction. The simulated and experimental results for the surge suppression characteristics are compared and evaluated for designed protype 1[kVA] NCT.

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Characteristics of Vibration and Sound Radiated from Rails of Concrete Slab Tracks for Domestic High Speed Trains (국내 고속 철도 콘크리트 슬라브 궤도의 진동 및 방사 소음 해석)

  • Ryue, Jungsoo;Jang, Seungho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.7
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    • pp.605-616
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    • 2013
  • An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

Noise Reduction Algorithm For The Detection of Fine Ion Signals in Residual Gas Analyzer (잔류가스분석기의 질량 스펙트럼 검출 성능 향상을 위한 잡음제거 알고리즘)

  • Heo, Gyeongyong;Choi, Hun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.68 no.1
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    • pp.102-107
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    • 2019
  • This paper proposes a method to improve the mass spectral detection performance of the residual gas analyzer. By improving the mode estimation method for setting the threshold value and improving the additive noise elimination method, it is possible to detect mass spectrums having low peak values of the threshold level difficult to distinguish from noise. Ion signal blocks for each mass index with noise removed by the improved method are effective for eliminating invalid ion signals based on the linear and quadratic fittings. The mass spectrum can be obtained from the quadratic fitted curves for the reconstructed ion signal block using only the valid ion signals. In addition, the resolution of the mass spectrum can be improved by correcting the error caused by the shift of the spectral peak position. To verify the performance of the proposed method, computer simulations were performed using real ion signals obtained from the residual gas analysis system under development. The simulation results show that the proposed method is valid.

A Study on the Application Ratio of ASIR in Abdominal CT (복부 CT 검사에서 ASIR의 적용율에 대한 연구)

  • Kim, Hyeon-jin;Jeong, Bong-jae
    • Journal of the Korean Society of Radiology
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    • v.13 no.1
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    • pp.95-101
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    • 2019
  • The purpose of this study is to reduce the dose to the patient by different application of ASIR according to the Body Mass Index (BMI). In particular, we wanted to find out the application values of ASIR that are most appropriate for the standard weight. Studies have shown that increasing the application of ASIR to 50% in patients with a body mass index of 25 or less reduces CTDIvol 58.17% and DLP 60.49% compared to using only FBP. A comparative analysis of the noise by the BMI and the SNR values found that the noise increased as the BMI increased, but the application of ASIR resulted in less noise than the FBP alone. In addition, it was found that the more ASIR is applied, the more SNR is increased.