Noise In Measured Data Research Articles

Parameter Estimation for Traffic Noise Models Using a Harmony Search Algorithm

A technique has been developed for predicting road traffic noise for environmental assessment, taking into account traffic volume as well as road surface conditions. The ASJ model (ASJ Prediction Model for Road Traffic Noise, 1999), which is based on the sound power level of the noise emitted by the interaction between the road surface and tires, employs regression models for two road surface types: dense-graded asphalt (DGA) and permeable asphalt (PA). However, these models are not applicable to other types of road surfaces. Accordingly, this paper introduces a parameter estimation procedure for ASJ-based noise prediction models, utilizing a harmony search (HS) algorithm. Traffic noise measurement data for four different vehicle types were used in the algorithm to determine the regression parameters for several road surface types. The parameters of the traffic noise prediction models were evaluated using another measurement set, and good agreement was observed between the predicted and measured sound power levels.

Study on Noise Attenuation Laws and Control Methods of the Transformer

The mechanism and characteristics of substation transformer noise are introduced in this paper. Based on the recent measured noise data of 220 kV, 500 kV and 750 kV substations, the noise source characteristics of transformer and the attenuation laws in noise transmission are analyzed. It is hoped that this paper can offer some measures and suggestions for controlling the noise of transformer substation. Lastly but not least it will provide some references for noise control during the new substation’s design and construction process.

Seismic site response of unstable steep slope using noise measurements: the case study of Xemxija Bay area, Malta

Abstract. Landslide phenomena involve the northern coast of Malta, affecting in particular the urban area of Xemxija. Limestones overlying a clayey formation represent the shallower lithotypes that characterize the surficial geology of this area, where lateral spreading phenomena and rockfalls take place. Ambient noise records, processed through spectral ratio techniques, were analysed in order to characterize the dynamic behavior of the rock masses affected by the presence of fractures linked to the landslide body existing in the area. Experimental spectral ratios were also calculated after rotating the horizontal components of the seismic signal, and a direct estimate of the polarization angle was also performed in order to investigate the existence of directional effects in the ground motion. The results of the morphologic survey confirmed the existence of large cliff-parallel fractures that cause cliff-edge and unstable boulder collapses. Such phenomena appear connected to the presence, inside the clay formation, of a sliding surface that was identified through the interpretation of the noise measurement data. The boundaries of the landslide area appear quite well defined by the pronounced polarization effects, trending in the northeastern direction, observed in the fractured zone and in the landslide body in particular.

건축물 내외부에 설치된 비상용 발전기 소음영향 평가 및 대책방안 사례연구

Recently, data centers are being established because IT and telecommunication industries are growing. The data centers have to install emergency generators to prevent unexpected shutdown of the electrical power supply. When the data centers are located in the densely populated urban area, the operating noise of the emergency generators can be a cause of people`s complaints. In this case, it is necessary to establish effective countermeasure by noise & vibration specialists. To achieve this, noise reduction measure using noise measurement data and 3D noise analysis method have been employed in this study.

Characterization of Channel-Diameter-Dependent Low-Frequency Noise in Silicon Nanowire Field-Effect Transistors

The low-frequency noise in the silicon nanowire field-effect transistor (SNWFET) is characterized using SNWFETs with different channel diameters dNW. The current density and the simulation result indicate that the volume inversion as manifested by the spatial charge distribution is enhanced in smaller dNW. The measured noise data are discussed based on the number and correlated mobility fluctuation model. It is shown that the low-frequency noise decreases in smaller dNW. This dNW-dependent noise behavior is clarified in terms of the effective oxide trap density and the fraction of inversion charges near the Si-SiO2 interface.

Estimating historic exposures at the European Gaseous Diffusion plants

This paper describes the methods and results of an occupational exposure assessment covering 30 years of operation of the EURODIF establishment (1978-2008). The exposure assessment includes radiological, physical and chemical hazards, and takes into account of organizational changes at the establishment. Furthermore, it includes efforts to better quantify the levels of exposures using available industrial hygiene and health physics data. In total, 227 workers participated in the assessment of 26 different occupational exposures in 102 general workstations through 1978-2008. Only 7% of exposure levels were rectified by experts for internal consistency reasons. Noise, heat, trichloroethylene and soluble uranium compounds were the most prevalent exposures at the plant although their levels tended to decrease across time. Assessments of occupational exposure to noise based on JEM exposure levels were fairly well correlated with noise measurement data (Spearman's correlation coefficient, ρ=0.43) while JEM-based assessments of uranium exposure were not well correlated with uranium atmospheric measurements. This study demonstrates the importance of non-radiological exposure in the nuclear fuel industry and highlights the difficulties in managing the risks arising from these exposures. Occupational exposures remain difficult to quantify due to the scarcity of reliable monitoring data and the absence of binding occupational exposure limits for some of considered hazards.

Thermal Phase Noise Measurements in Optical Fiber Interferometers

We present measurement data of fundamental thermal noise in a 40-m fiber optic Mach-Zehnder interferometer (MZI) using 80-μm-diameter optical fiber. To extend the measurements to low frequencies (below 500 Hz), the experimental setup is carefully designed to minimize ambient noise, thermal drift, and the phase and amplitude noise of the lasers. These experimental results are compared with theoretical predictions for the magnitude of the fundamental thermal noise in fiber, due to both thermodynamic temperature fluctuations and spontaneous length fluctuations. The experimental data, using two different solid-state lasers with two different emission wavelengths (1319 and 1550 nm), is in reasonable agreement with both theories over frequencies ranging from 20 Hz to 100 kHz. In terms of strain resolution, this paper demonstrates a fundamental thermal noise limit of approximately one femtostrain/rt(Hz) for a 40-m fiber optic MZI.

Estimating health related costs and savings from balcony acoustic design for road traffic noise

A multi-faceted study is conducted with the objective of estimating the potential fiscal savings in annoyance and sleep disturbance related health costs due to providing improved building acoustic design standards. This study uses balcony acoustic treatments in response to road traffic noise as an example. The study area is the State of Queensland in Australia, where regional road traffic noise mapping data is used in conjunction with standard dose–response curves to estimate the population exposure levels. The background and the importance of using the selected road traffic noise indicators are discussed. In order to achieve the objective, correlations between the mapping indicator (LA10(18hour)) and the dose response curve indicators (Lden and Lnight) are established via analysis on a large database of road traffic noise measurement data. The existing noise exposure of the study area is used to estimate the fiscal reductions in health related costs through the application of simple estimations of costs per person per year per degree of annoyance or sleep disturbance. The results demonstrate that balcony acoustic treatments may provide a significant benefit towards reducing the health related costs of road traffic noise in a community.

On the Excess Noise Factor $\Gamma$ of a FET Driven by a Capacitive Source

The excess noise factor Γ , also known as Ogawa's noise factor, is frequently used in the literature on optical receivers to calculate the noise and sensitivity of FET front-ends. After revisiting its definition and clarifying its applications and limitations, we derive an analytical expression for Γ in terms of the channel noise factor γ, the gate noise factor δ , and the correlation coefficient c. We explain the difference between Γ and γ and discuss the dependence of Γ on the source (photodetector) capacitance. The latter dependence, which is weaker than previously thought, is verified by circuit simulations. Additional insight is obtained by complementing van der Ziel's noise model with Pospieszalski's noise model. Finally, we use the derived expression for Γ to calculate its value from measured noise data of a 0.18- μm CMOS technology.

음향도구 착용 근로자의 소음노출 실태에 관한 연구

There are hundreds of thousands call center workers wearing acoustic device. However, researches and noise exposure measurements on the noise transmitted from acoustic devices have seldom been performed due to the difficulty of measurement and to the absence of the measuring method in Korea. The aim of this study is to set up management measures to protect hearing loss on the call operator by acquiring measurement data of noise transmitted from the headset. Noise exposure measurements of 17 operators were performed in 7 call centers and head and Torso simulator method in compliance with the ISO standard 11904-2 was used for the measurement of noise transmitted from the headset. Sound pressure levels(SPL) transmitted from the headset were 73.2~86 dB(A). The operator exposed to the highest SPL set up his volume control at 9 which was the highest volume level. The volume control level, adjustable from 1 to 9, could be identified 12 out of 17 operators and the range of volume levels was 4.5~9. As a result of pearson correlation analysis, the correlation between volume level and SPL transmitted from the headset showed high relation as significance at the 0.672 level(p<0.05). To protect hearing loss of call center operators, it is more practical and effective measure to limit the volume level below the noise exposure level, i.e. 85 dB(A), rather than to carry out noise monitoring considering cost-effective aspect.

포장노면과 타이어간의 마찰음 분석을 통한 교통소음예측 소프트웨어 개발

고속도로 이용차량의 증가와 함께 차량의 대형화와 고속화로 인해 고속도로 교통 소음레벨이 높아지고 있으며 저소음 포장노면 및 방음시설 설치 요청도 급격하게 증가하고 있다. 따라서 고속도로 교통소음으로 인한 민원예방과 함께 효율적이고 경제적인 소음저감 대책을 수립하기 위해서는 정확한 소음 예측 기술 마련이 필요하다. 본 연구에서는 시험도로에 포설된 다양한 포장노면에 대해서 CPX(Close Proximity Test) 및 Pass-by 소음 계측 방법을 혼용한 소음 계측 데이터를 이용하였고 차종별 단독 주행 시험을 실시하여 차량 및 노면별 음향파워레벨 산정식이 마련된 데이터를 이용하였다. 아울러, 상기 산정식의 정확성을 검증하기 위하여 고속도로 12개 지점에 대한 총 38회의 소음 계측한 데이터를 이용하여 해당 지점에 대한 소음 예측 모델을 구성하여 측정값과 예측값을 비교 평가하였다. 최종적으로 3차원 GUI 기능을 지원하는 도로교통 소음 예측 프로그램 KRON(Korea Road Noise)을 개발하였다. 이와 더불어 각 포장형태별 및 차종별에 따른 소음특성을 분석하였다. Domestic economic development, industrialization, and urbanization have brought along not only increased highway traffic but also elevated traffic noise levels. Thus, it is necessary to accurately predict the traffic noise levels in order to address the public demand of alleviating the noise levels in urban areas. In this study, the method of evaluating the sound power level of road traffic was investigated in terms of considering the types of road surface and vehicle, based on previous researches. Regarding CPX (Close Proximity Test) and Pass-by test, the measured noise data of Test Road of Korea Highway Corporation were utilized in order to construct the database of sound power levels of various vehicles. Specifically, the 38 noise measurement and analysis in 1/1-octave band frequencies at 12 pre-selected sites were carried out, considering topography and road surface. Finally, the comparison study was conducted between predicted and measured data in terms of traffic noise. The traffic noise prediction was based on the KRON (Korea Road Noise) program, which was developed being equipped wit 3-dimensional GUI. In addition, the traffic noise characteristics were evaluated in terms of vehicle types and pavement surface conditions.

Fan noise visualization and noise source identification by using nearfield acoustical holography.

A nearfield acoustical holography (NAH) method combined with a non-stationary source compensation procedure is applied to identify the noise sources of two open fans. The measured noise data of a low-speed, small fan indicate the highest peak levels at the blade passing frequencies (BPFs) of 102 and 204 Hz. It is observed that there is no noise component induced by vortex shedding at the blade tips, or leading or trailing edges of the small fan. It is also observed that the structural resonance frequencies of the small fan blades are not coincident with the BPFs: thus, the structural vibration responses of the blades contribute insignificantly to the fan noise. The NAH results of the small fan show acoustic pressure fluctuations on the blade surfaces at the BPFs. The measured noise data of a high-speed, large fan show the frequency components associated with BPFs as well as vortices shed at blade edges. Similar to the small fan case, the resonance frequencies of the fan blades cannot be observed in the measured acoustic data. The NAH results of the high-speed, large fan successfully exhibit acoustic pressure fluctuations at BPFs as well as noise patterns radiated from the vortex shedding.

Investigation of Thermal Noise Factor in Nanoscale MOSFETs

In this paper, we investigate the channel thermal noise in nanoscale MOSFETs. Simple analytical model of thermal noise factor in nanoscale MOSFETs is presented and it is verified with accurately measured noise data. The noise factor is expressed in terms of the channel conductance and the electric field in the gradual channel region. The proposed noise model can predict the channel thermal noise behavior in all operating bias regions from the long-channel to nanoscale MOSFETs. From the measurement results, we observed that the thermal noise model for the long-channel MOSFETs does not always underestimate the short-channel thermal noise.

Tracking noisy limit cycle oscillation with nonlinear filters

For engineering systems, the dynamic state estimates provide valuable information for the detection and prediction of failure due to noise and vibration. From this perspective, nonlinear filtering techniques are applied to the problem of state estimation of dynamical systems undergoing noisy limit cycle oscillation. Specifically, the extended Kalman filter, ensemble Kalman filter and particle filter are used to track the limit cycle oscillations of a Duffing oscillator using noisy observational data. The noisy limit cycle oscillations feature highly non-Gaussian trends. The efficiency and limitations of the extended Kalman filter, ensemble Kalman filter and particle filter in tracking limit cycle oscillations are examined with respect to the model and measurement noise and sparsity of measurement data. For the limit cycle oscillations considered here, it is demonstrated that the ensemble Kalman filter and particle filter outperform the extended Kalman filter in the presence of sparse observational data or strong measurement noise. For moderate measurement noise and frequent measurement data, the ensemble Kalman filter and particle filter perform equally well in comparison to the extended Kalman filter.

Estimation of kinetic parameters of composite materials during the cure process using the combined wavelet regularization method

The limitation of the experimental methods in thermophysical characterization of composite materials leads to an increased use of inverse parameter estimation techniques. However, in some situations the convergence of the inverse algorithm is impossible due to the correlation of the involved parameters and the existing noises in measurement data. Several different approaches have been used to tackle this problem. In this article, a new approach is utilized to solve it. This new technique combines the wavelet denoising and Levenberg-Marquardt regularization method. In order to examine this technique, a highly ill-posed problem is considered as a test case, that is, the estimation of the composite kinetic parameters during the cure process.

Determination of the Air/Fiber Conductivity of Mineral Wool Insulations in Building Applications Using Nonlinear Estimation Methods

The limitation of the experimental methods in determining the thermal conductivity due to the air/fiber conduction in mineral wools leads the use of inverse parameter estimation techniques. However, in some circumstances, the convergence of the inverse solution is impossible due to the correlation of the involving parameters and the existing noises in measurement data. In this article two relations are obtained to model thermal conductivity of the air/fiber conduction k(T, ρ), for glass fiber and rock wool insulations in temperatures between 0°C and 20°C, commonly encountered in building applications. Levenberg Marquardt's (LM) method is used for estimating of the unknown parameters in this article. Considering the nonlinear nature of the inverse problem and the correlation of the involving parameters and the existing noises in measurement data, the convergence of the problem is acceptable. The results obtained by the estimated parameters agree extremely well with experimental measurements of the Heat Flow Meter (HFM) apparatus conducted at the Building and Housing Research Center (BHRC).

Effects of intensive care unit noise on patients: a study on coronary artery bypass graft surgery patients

The aim of this study was to measure the noise levels in specific locations of an intensive care unit and determine the disturbance levels of patients owing to noise. Studies have shown that hospital noise is a potential stressor for patients. Noise levels measured in the intensive care unit are mostly far beyond the recommended standards for hospitals, and generally measured around 60-70 dB (A). Although there are a few studies on noise levels in the intensive care unit, no study could be found that compares 24-hour intensive care unit noise measurement data at several locations of intensive care unit. The study was conducted with 35 coronary artery bypass graft surgery patients. The intensive care unit noise level was measured by using Bruel & Kjaer 2144 Model Frequency Analyzer next to the bed of each patient. A patient's disturbance owing to the intensive care unit noise was questioned. Noise levels ranged between 49 and 89 dB (A) with a mean of 65 dB (A). Peak noise levels were measured as high as 89 dB (A). The noise levels measured at different locations in the intensive care unit did not differ significantly. Noises created by other patients, those who were admitted from emergency room and operating room into intensive care unit, monitor alarms, conversations among staff were the most disturbing noise sources for patients. The patients who were located in the bed which was closer to the nurses' station were more affected by the intensive care unit noise than other patients. Having a previous intensive care unit experience also affected the patients' disturbance levels owing to noise. Nurses are in key positions where they can identify physical, psychological and social stressors that affect patients during their hospital stay. Staff education, planned nursing activities and proper design of intensive care unit may help combat this overlooked problem.

Effect of sliding friction on gear noise based on a refined vibro-acoustic formulation

An improved source-path-receiver model of a single mesh geared system is developed and validated to quantify the effect of sliding friction between gear teeth on the structure-borne whine noise. The source sub-system of a spur gear pair predicts interfacial bearing forces in the line-of-action and off line-of-action directions for two whine excitations (static transmission error and sliding friction). Next, a finite element model of the gearbox with embedded bearing stiffness matrices is developed to characterize the structural paths and to calculate the surface velocity distributions. Predictions are first validated by comparing with structural modal tests and transfer function measurements from gear mesh to the housing plates. Radiated noise is then estimated by using two approximate methods, namely the Rayleigh integral method and a substitute source technique. The overall vibro-acoustic model is validated by comparing radiated sound pressure calculations with measured noise data over a range of operating torques. The proposed formulation provides an efficient analytical and computational tool to quantify the relative contribution of sliding friction to the structure-borne noise, which is found to be significant when the transmission error is minimized say via tooth modifications.

Nonlinear filters for chaotic oscillatory systems

This paper examines and contrasts the feasibility of joint state and parameter estimation of noise-driven chaotic systems using the extended Kalman filter (EKF), ensemble Kalman filter (EnKF), and particle filter (PF). In particular, we consider the chaotic vibration of a noisy Duffing oscillator perturbed by combined harmonic and random inputs ensuing a transition probability density function (pdf) of motion which displays strongly non-Gaussian features. This system offers computational simplicity while exhibiting a kaleidoscope of dynamical behavior with a slight change of input and system parameters. An extensive numerical study is undertaken to contrast the performance of various nonlinear filtering algorithms with respect to sparsity of observational data and strength of model and measurement noise. In general, the performance of EnKF is better than PF for smaller ensemble size, while for larger ensembles PF outperforms EnKF. For moderate measurement noise and frequent measurement data, EKF is able to correctly track the dynamics of the system. However, EKF performance is unsatisfactory in the presence of sparse observational data or strong measurement noise.

A new correlation method for high sensitivity current noise measurements

The properties of a differential transconductance amplifier coupled with a four channel measurement system are exploited in order to reach a very high sensitivity in current noise measurements. In particular, it is demonstrated that, in proper conditions, the noise contributions coming from the active and passive devices that make up the transresistance amplifier can be virtually eliminated. Moreover, the proposed measurement method allows the evaluation of the impedance of the device under test from noise measurement data. Actual measurement results are also reported that demonstrate the effectiveness of the proposed approach.