Loading [MathJax]/jax/output/CommonHTML/jax.js
  • Title/Summary/Keyword: 소음 감소

Search Result 502, Processing Time 0.028 seconds

Usefulness of Acoustic Noise Reduction in Brain MRI Using Quiet-T2 (뇌 자기공명영상에서 Quiet-T2 기법을 이용한 소음감소의 유용성)

  • Lee, SeJy;Kim, Young-Keun
    • Journal of radiological science and technology
    • /
    • v.39 no.1
    • /
    • pp.51-57
    • /
    • 2016
  • Acoustic noise during magnetic resonance imaging (MRI) is the main source for patient discomfort. we report our preliminary experience with this technique in neuroimaging with regard to subjective and objective noise levels and image quality. 60 patients(29 males, 31 females, average age of 60.1) underwent routine brain MRI with 3.0 Tesla (MAGNETOM Tim Trio; Siemens, Germany) system and 12-channel head coil. Q-T2 and T2 sequence were performed. Measurement of sound pressure levels (SPL) and heart rate on Q-T2 and T2 was performed respectively. Quantitative analysis was carried out by measuring the SNR, CNR, and SIR values of Q-T2, T2 and a statistical analysis was performed using independent sample T-test. Qualitative analysis was evaluated by the eyes for the overall quality image of Q-T2 and T2. A 5-point evaluation scale was used, including excellent(5), good(4), fair(3), poor(2), and unacceptable(1). The average noise and peak noise decreased by 15dBA and 10dBA on T2 and Q-T2 test. Also, the average value of heartbeat rate was lower in Q-T2 for 120 seconds in each test, but there was no statistical significance. The quantitative analysis showed that there was no significant difference between CNR and SIR, and there was a significant difference (p<0.05) as SNR had a lower average value on Q-T2. According to the qualitative analysis, the overall quality image of 59 case T2 and Q-T2 was evaluated as excellent at 5 points, and 1 case was evaluated as good at 4 points due to a motion artifact. Q-T2 is a promising technique for acoustic noise reduction and improved patient comfort.

Active Control of Propagated Noise through Opening of Enclosures Surrounding a Noise Source (음원을 둘러싼 인클로저 개구부를 통해 전파되는 소음의 능동 제어)

  • Lee, Hanwool;Hong, Chinsuk;Jeong, Weuibong
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.25 no.4
    • /
    • pp.223-231
    • /
    • 2015
  • Enclosures are widely used to alleviate the contribution of machinery noise. It has been long concerned with the noise transmission through the access openings of the enclosures. In this study, we investigate active noise control technology for reduction of the transmission. A numerical model based on the acoustic boundary element method is first established. Using the numerical model, the acoustic transfer functions of the field points over the opening to the primary source at arbitrary locations are estimated. The feedforward control to minimize the acoustic power through the opening is then numerically implemented. The controller drives the secondary source to destructively interfere the noise transmission through the opening. Finally, a parametric study is conducted to evaluate the effects of the location and the number of the microphones on the control performance. Furthermore, the effects of the location of the secondary source on the performance of active noise control are investigated. It is followed that the control system implemented in this study leads to a significant reduction of about 31.5 dB in the sound power through the opening using only one secondary source located at the optimized position.

Active Control of Transmitted Noise through Opening of Enclosures Surrounding a Noise Source (음원을 둘러싼 인클로저 개구부를 통해 투과되는 소음의 능동 제어)

  • Lee, Hanwool;Hong, Chinsuk;Jeong, Weuibong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2013.04a
    • /
    • pp.796-802
    • /
    • 2013
  • In this study, we investigates active control technology to reduce the noise transmitted to the outside through the opening of enclosures. A numerical model based on acoustic boundary element method is first established. Using the numerical model, the acoustic transfer functions of the field points over the opening to the primary source at arbitrary locations are estimated. The feedforward control to minimize the acoustic power through the opening is then numerically implemented. The controller generates the secondary source to destructively interfere the noise transmission through the opening. Finally, a parametric study is conducted to evaluate the effects of the location and the number of the microphones on the control performance. Furthermore, the effects of the location of the secondary source on the performance of active noise control are investigated. It is followed that the control system implemented in this study leads to a significant reduction of about 35dB in sound power through the open using only on secondary source located at the optimized position.

  • PDF

A Study on the Noise Source Identification of Refrigerator Compressor (냉장고용 압축기 소음원 규명에 관한 연구)

  • O, Jae-Eung;Lee, Chang-Ho;Lee, Myeong-Ryeol;Yeom, Seong-Ha
    • The Journal of the Acoustical Society of Korea
    • /
    • v.6 no.1
    • /
    • pp.48-57
    • /
    • 1987
  • It is well known that the major noise source of Refrigerator is compressor, and due to the tendency of higher quality and more lighting of manufactured goods, the importance of prevention and reduction of a noise is increasing. In this paper, in order to prevent and reduce such a noise, sound pressure level and acoustic intensity are measured for compressor, and the result of these measurements, the noise radiation characteristics of compressor are reconized. And the experimental modal analysis is applied to the compressor to identify the noise sourcce. As the results of this study, we come to know that the spring, which is used to reduce vibration, does not reduce vibration efficiently, and compressor shell and its mounting system effect the noise radiation.

  • PDF

Effect of the Inner Material and Pipe Geometry on the Flow and Induced Radiated Noise (파이프 내 흡음재 및 형상에 따른 유동 및 방사소음에 대한 수치해석적 연구)

  • Lee, Su-Jeong;Lim, Hee-Chang
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.38 no.5
    • /
    • pp.423-430
    • /
    • 2014
  • Noise and vibration, which occur in a pipe, are usually caused by the interaction between the turbulent flow and nearby wall. Although it can be estimated by a simple case of expanded pipes having complex turbulent flow, the radiated noise is highly dependent upon the size, shape, and thickness of the given model. In addition, the radiated noise propagates and has serious interference and destabilization effects on the surrounding systems, which can lead to fatigue fracture and failure. This study took advantage of the variety of commercial programs, such as FLUENT (flow solver), NASTRAN (dynamic motion solver of complex structures) and VIRTUAL LAB (radiated noise solver) based on the boundary element method (BEM), to understand the underlying physics of flow noise. The expanded pipe has separation and a high pressure drop because of the abrupt change in the cross-section. Based on the radiated noise calculations, the noise level was reduced to around 20 dB in the range of 100-500 Hz.

The Influence of MR Gradient Acoustic Noise on fMRI (MR 경사 자계 소음이 뇌기능 영상에 미치는 영향)

  • S. C. Chung
    • Investigative Magnetic Resonance Imaging
    • /
    • v.2 no.1
    • /
    • pp.50-57
    • /
    • 1998
  • MR acoustic sound or noise due to gradient pulsings has been one of the problems in MRI, both in patient scanning as well as in many areas of psychiatric and neuroscience research, such as brain fMRI. Especially in brain fMRI, sound noise is one of the serious noise sources which obscures the small signals obtainable from the subtle changes occurring in oxygenation status in the cortex and blood capillaries. Therfore, we have studied the effects of acoustic or sound noise arising in fMR imaging of the auditory, motor and visual cortices. The results show that the acoustical noise effects on motor and visual responses are opposite. That is, for the motor activity, it shows an increased total motor activation while for the visual stimulation, corresponding(visual) cortical activity has diminished substantially when the subject is exposed to a loud acoustic sound. Although the current observations are preliminary and require more experimental confirmation, it appears that the observed acoustic-noise effects on brain functions, such as in the motor and visual cortices, are new observations and could have significant consequences in data observation and interpretation in future fMRI studies.

  • PDF

Noise Analyses of VVVF Inverter and DC/DC Converter for Maglev Train (자기부상열차용 VVVF 인버터 및 DC/DC 컨버터의 소음해석)

  • 김현실;김재승;강현주;김봉기;김상렬
    • The Journal of the Acoustical Society of Korea
    • /
    • v.22 no.5
    • /
    • pp.337-344
    • /
    • 2003
  • In DC/DC converter and VVVF inverter, which are the must dominant noise sources of Maglev train, noise is radiated from core and coil excited by MS(Magnetostriction). The main noise source of DC/DC converter is transformer whose spectrum shows strong peaks associated with harmonics of exciting frequency, On the other hand, LIM/VVVF noise is dominated by the harmonics of switching frequency, whereas harmonics of exciting frequency are not significant. As switching frequency is increased in VVVF inverter, it is shown that the harmonics are shifted to higher frequency range. If switching frequency is increased from 700㎐ to 2 ㎑, It is measured that noise can be reduced by 5 to 6 ㏈. Since complete mathematical description of MS phenomena is far beyond the present technology, vibration spectrum is investigated qualitatively in this paper, where effect of increasing switching frequency is confirmed.

A General Acoustic Drone Detection Using Noise Reduction Preprocessing (환경 소음 제거를 통한 범용적인 드론 음향 탐지 구현)

  • Kang, Hae Young;Lee, Kyung-ho
    • Journal of the Korea Institute of Information Security & Cryptology
    • /
    • v.32 no.5
    • /
    • pp.881-890
    • /
    • 2022
  • As individual and group users actively use drones, the risks (Intrusion, Information leakage, and Sircraft crashes and so on) in no-fly zones are also increasing. Therefore, it is necessary to build a system that can detect drones intruding into the no-fly zone. General acoustic drone detection researches do not derive location-independent performance by directly learning drone sound including environmental noise in a deep learning model to overcome environmental noise. In this paper, we propose a drone detection system that collects sounds including environmental noise, and detects drones by removing noise from target sound. After removing environmental noise from the collected sound, the proposed system predicts the drone sound using Mel spectrogram and CNN deep learning. As a result, It is confirmed that the drone detection performance, which was weak due to unstudied environmental noises, can be improved by more than 7%.

Characteristics of noise generated during treatment in dental clinic

  • Choi, Mi-Suk;Ji, Dong-Ha
    • Journal of the Korea Society of Computer and Information
    • /
    • v.27 no.5
    • /
    • pp.181-188
    • /
    • 2022
  • In this paper, we proposed of the results of the noise level and appropriate conversation distance by applying the noise characteristics generated during treatment at a dental clinic to the NR-curve and PSIL. As a result of analyzing the noise characteristics during treatment at a dental clinic, it was analyzed that the noise level exceeded 60dB(A), which is the health preservation limit value caused by noise, and the noise level increased as the frequency increased. the result of evaluation applying it to the NR curve, some treatment exceeded the workplace noise standard, and as a result of analyzing the level of conversational disturbance between the worker and the patient, it is desirable to have the conversation at a distance of less than 1M for accurate communication. In order to improve the quality of medical service in dental clinic and to reduce dental fear, it is judged that soundproofing protective equipment is provided to workers, and soundproofing measures are needed for noise sources (treatment devices used in treatment) and sound sources (patients and workers).