• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
• /
• pp.581-587
• /
• 1997

Numerical predictions of aerodynamic noise radiated by subsonic rotors are carried out. A time domain approach for Ffowcs-Williams Hawkings equation of acoustic analogy is used in developing a comprehensive rotor/fan noise prediction program to handle both arbitrary blade shapes and loading conditions. Since only the aeroacoustic aspects of rotors are considered here, the calculations are carried out for rotors with simple aerodynamic characteristics. Broadband noise from ingestion of turbulence is also considered. By incorporating discrete frequency noise prediction of steady loading with broadband spectrum, much better correlation at the low frequency region with experimental data is obtaind. The contributions from different noise mechanisms can also be analysed through this method.

• 대한토목학회논문집
• /
• 제38권4호
• /
• pp.587-593
• /
• 2018

현재 널리 사용되고 있는 도로교통소음 예측프로그램들은 국외 예측모형을 바탕으로 제작된 것이 대부분이다. 이에 본 연구에서는 국내 도로교통환경에 적합한지를 알아보기 위해 국외 예측모형에 대한 검증을 수행하였다. 또한, 예측모형마다 도로교통소음 발생에 대한 영향요인이 다르기 때문에 주요 요인들에 대한 분석 및 고찰을 선행하였다. 본 연구에서는 도로교통소음 예측 시 사용되고 있는 영향인자와 기존 예측모형에 대하여 고찰하고, 교통환경 및 도로기하구조를 고려하여 주행차량의 발생 소음에 영향을 미치는 영향인자와의 관계를 다중회귀분석을 통한 예측모형으로 도출하였다. 나아가 기존의 도로교통소음 예측모형(국립환경과학원(NIER), 독일의 RLS-90)과 도출된 도로교통소음 예측모형의 실측값을 적용하여 비교 검증 결과, 오차의 절대값 합은 NIER, RLS-90, 모형값 순으로 나타났다. 따라서 본 모형식이 향후 도로교통소음 예측 모델링에 대한 연구의 참고자료로 활용할 수 있는 기틀을 제공하고자 한다.

• 한국유체기계학회 논문집
• /
• 제2권2호
• /
• pp.46-56
• /
• 1999

This study is on the performance prediction and design of a sirocco fan. Slip coefficient is very important factor for the performance analysis of a centrifugal-type fan. Because generally used slip coefficient equations of backward curved centrifugal fan are not appropriate for forward curved sirocco fan, in this study a proper slip coefficient equation for a sirocco fan is suggested. Using this equation performance prediction program for sirocco fan is composed of and also included the total noise prediction that include the turbulent noise at the fan inlet and boundary layer noise. A comparison between the values obtained from performance prediction program and experimental values shows that the program predicts the sirocco fan performance in a practical rate.

• 한국통신학회논문지
• /
• 제21권5호
• /
• pp.1172-1179
• /
• 1996

General adaptive noise canceller(ANC) suffers from the misadjustment of adaptive filter weights, because of the gradient-estimate noise at steady state. In this paper, an adaptive noise cancellation algorithm with speech detector which is distinguishing speech from silence and adaptation-transient region is proposed. The speech detector uses property of adaptive prediction-error filter which can filter the highly correlated speech. To detect speech region, estimation error which is the output of the adaptive filter is applied to the adaptive prediction-error filter. When speech signal apears at the input of the adaptive prediction-error filter. The ratio of input and output energy of adaptive prediction-error filter becomes relatively lower. The ratio becomes large when the white noise appears at the input. So the region of speech is detected by the ratio. Sign algorithm is applied at speech region to prevent the weights from perturbing by output speech of ANC. As results of computer simulation, the proposed algorithm improves segmental SNR and SNR up to about 4 dBand 11 dB, respectively.

• 한국음향학회지
• /
• 제13권1호
• /
• pp.57-62
• /
• 1994

발생된 도로교통소음 예측을 위한 새로운 방법을 제시하고자 하며, 본 연구에서 도시지역 도로 한 Block내에서는 도로교통 특성이 유사하므로 한 Block을 한 Box로 간주하였다. 이 예측방법은 한 Block 내에서 발생한 다양한 도로교통소음을 예측할 수 있다. 본 Model의 검증은 도로에서 실측한 소음레벨 및 교통특성을 활용하여 실시하였으며, 실측된 소음레벨과 예측된 소음레벨의 상관성을 살펴본 결과 높은 상판관계를 갖고 있는 것으로 나타났다.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 1998년도 강연회 및 연구개발 발표회 논문집
• /
• pp.63-72
• /
• 1998

This study Is on the performance prediction and design of sirocco fan. Slip coefficient is very important factor for the performance analysis of centrifugal-type fan. Because generally used slip coefficient equations of backward curved centrifugal fan are not appropriate for forward curved sirocco fan, in this study a proper slip coefficient equation for sirocco fan is suggested. Using this equation performance prediction program for sirocco fan is composed and also included the total noise prediction that include turbulent noise at the fan Inlet and boundary layer noise. A comparison between the values obtained from performance prediction program and experimental values shows that the program predicts the sirocco fan performance in a practical rate.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.78-83
• /
• 2000

Exterior noise generated by the aircraft induces a serious noise pollution near the airport. For the prediction of an exterior noise radiation of aircraft an empirical formula is employed to model the acoustic sources. It is shown that the fan/compressor noise is the most dominant part of the acoustic sources in all cases.

• 환경영향평가
• /
• 제15권2호
• /
• pp.93-100
• /
• 2006

In general, the verification to prediction formula in a national road and the main street of a town has been used recklessly in Korea. Therefore we investigated the validity of an existing prediction formula (NIER(87, 99), TR-Noise, KLC(2002)) with correction relationship which was based on both the prediction formular from apartment complex in the field and height 1.5m from the surface level. On the results of measuring the noise level form an isolated distance, the noise level showed that it was 4.5~5.5dB(A) by reason of becoming 2 folder far from a source. From the distribution of noise level measured by the apartment floors, the measurement point (1st floor) was 58.7~71.4dB(A) at its lowest level and the middle floors (3, 5, 7 and 10) were the highest distribution of noise level. From the analysis results on the application validity to an existing prediction formular (NIER(87, 99), TR-Noise, KLC(2002)) in the height 1.5m, the correction coefficients were 0.95~0.96 and the measured values were reasonably close to the predicted values, indicating the validity and adequacy of the predicted models. KLC(2002) model was found accurate within 3dB(A) with 36 data out of the total 42 data, showing the most accuracy among the predict models. However, the developed models have to improve the accuracy with a various of factors.

• 대한조선학회논문집
• /
• 제28권2호
• /
• pp.293-306
• /
• 1991

선박은 내부에 소음원을 가지고 있을 뿐 아니라 진동의 전달 특성이 좋은 강판 구조물이기 때문에 기진원과 소음원을 포함한 구조계및 주변 음장계까지 포함한 전체계에 대한 소음 예측을 수행하여야 한다. 이러한 선내 소음 환경을 예측하기 위하여 본 연구에서는 통계적 에너지 해석법을 이용하여 고차 진동의 전달 특성, 음장과 구조물과의 상호 작용 및 음장의 투과 손실등에 대한 해석 이론을 정식화하고 이를 바탕으로 선내 소음 예측을 위한 전산 프로그램을 개발하였다. 또, 소형 연안 여객선을 대상으로 하여 이론적 소음 예측 계산을 수행하고 실선 계측 결과와 비교하여 그 타당성을 확인하였으며, 공기음과 고체음에 대한 전달 특성을 분석하여 보았다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권12호
• /
• pp.3242-3265
• /
• 2023

Ensuring reliability of a machinery system involve the prediction of remaining useful life (RUL). In most RUL prediction approaches, noise is always considered for removal. Nevertheless, noise could be properly utilized to enhance the prediction capabilities. In this paper, we proposed a novel RUL prediction approach based on noise injection and a Kalman filter ensemble of modified bagging predictors. Firstly, we proposed a new method to insert Gaussian noises into both observation and feature spaces of an original training dataset, named GN-DAFC. Secondly, we developed a modified bagging method based on Kalman filter averaging, named KBAG. Then, we developed a new ensemble method which is a Kalman filter ensemble of KBAGs, named DKBAG. Finally, we proposed a novel RUL prediction approach GN-DAFC-DKBAG in which the optimal noise-injected training dataset was determined by a GN-DAFC-based searching strategy and then inputted to a DKBAG model. Our approach is validated on the NASA C-MAPSS dataset of aero-engines. Experimental results show that our approach achieves significantly better performance than a traditional Kalman filter ensemble of single learning models (KESLM) and the original DKBAG approaches. We also found that the optimal noise-injected data could improve the prediction performance of both KESLM and DKBAG. We further compare our approach with two advanced ensemble approaches, and the results indicate that the former also has better performance than the latters. Thus, our approach of combining optimal noise injection and DKBAG provides an effective solution for RUL estimation of machinery systems.