Noise Source Parameters Research Articles

Development of methodological approaches to conducting monitoring of traffic noise and its assessment using acoustic modelling methods

Introduction. At present, considerable attention is paid to the problems of noise pollution in urban and rural settlements. Transport is the main source of noise in the structure of complaints about unfavourable living conditions in dense urban areas. Material and methods. Materials for selecting the most significant criteria or grouping the objects of surveillance were in situ instrumental measurements of noise levels and the results of acoustic calculations obtained during the processing of an acoustic model. In situ measurements of noise levels were made in St. Petersburg on the territory of residential areas. The acoustic models were built using the software “Acoustics 3D”. Noise source parameters were set according to the data obtained during field measurements. Results. During the development of methodological approaches, the criteria for grouping the objects of surveillance were defined. In accordance with the selected criteria, were formed 8 surveillance groups. As a result of the measurements, the difference in noise levels between the typical points within the group was no found to exceed 2 dB. To verify the developed criteria here acoustic modelling was performed. Limitations. On the territory of St. Petersburg over the year, study included one thousand measurements. Conclusion. The developed criteria make it possible to expand the list of control objects while reducing labour costs for conducting socio-hygienic monitoring, while maintaining the objectivity of the results of the acoustic pollution levels of the territory.

Sensitivity analysis in core diagnostics

In the CORTEX project, methods to simulate neutron flux oscillations were enhanced and machine-learning based tools to determine the causes of measured neutron flux oscillations were developed, using the results of simulations as training and validation data. For a selected combination of those methods and tools, several sensitivity analyses were performed to assess their robustness and trustworthiness. The neutron flux oscillations were simulated using the tool CORE SIM+. It calculates the three-dimensional field of the neutron flux oscillations, which can be used to determine the response of neutron detectors at given locations. For the sensitivity analysis, the neutron flux oscillations were assumed to be caused by the vibration of one fuel element. It was investigated how selected input parameters like the core loading pattern, the burn up of the fuel elements, the neutronic core data, the geometry details of the vibrating fuel element, the chosen detectors, and other noise source parameters like the amplitude of the fuel element vibrations, affect the simulated neutron flux oscillations. A three dimensional fully convolutional neural network had been developed and trained during the CORTEX project to determine the cause and location of perturbations causing given measurements of in-core detectors in pressurized water reactors. The robustness of this network was tested by applying it to the simulated detector readings created during the sensitivity analysis.

Noise conversion of Schottky diodes in mm-wave detectors under different nonlinear regimes: modeling and simulation versus measurement

This paper presents and discusses several methods for predicting the low-frequency (LF) noise at the output of a mm-wave detector. These methods are based on the extraction of LF noise source parameters from the single diode under a specific set of bias conditions and the transfer or conversion of these noise sources, under different operating conditions including cyclostationary regime, to the quasi-dc output of a mm-wave detector constructed with the same model of diode. The noise analysis is based on a conversion-matrix type formulation, which relates the carrier noisy sidebands of the input signal with the detector output spectrum through a pair of transfer functions obtained in commercial software. Measurements of detectors in individual and differential setups will be presented and compared with predictions.

Distributed System for Noise Threat Evaluation Based on Psychoacoustic Measurements

An innovative system designed for the continuous monitoring of acoustic climate of urban areas was presen ted in the paper. The assessment of environmental threats is perf ormed using online data, acquired through a grid of engineered monitoring stations collecting comprehensive infor mation about the acoustic climate of urban areas. The grid of proposed devices provides valuable data for the p urpose of long and short time acoustic climate analysis. Dynamic estimation of noise source parameters and r eal measurement results of emission data are utilized to create dynamic noise maps accessible to the general public . This operation is performed through the noise source prediction employing a propagation model being o ptimized for computer cluster implementation requirements. It enables the system to generate noise maps in a reasonable time and to publish regularly map u pdates in the Internet. Moreover, the functionality of the s ystem was extended with new techniques for assessing noise-induced harmful effects on the human hearing system. The principle of operation of the dosimeter is based on a modified psychoacoustic model of hear ing and on the results of research performed with participation of volunteers concerning the impact of noise on hearing. The primary function of the dosimeter is to estimate, in real time, auditory effects which are caused by exposure to noise. The results of measurements and simulations performed by the system prototype are depicte d and analyzed. Several cases of long-term and short-term measurements of noise originating from various sou rces were considered in detail. The presented outcomes of predicted degree of the hearing threshold shift i nduced during the noise exposure can increase the awareness of harmfulness of excessive sound levels.

Online urban acoustic noise monitoring system

Concepts and implementation of the Online Urban Noise Monitoring System are presented. Principles of proposed solution used for dynamic acoustical maps creating are discussed. The architecture of the system and the data acquisition scheme are described. The concept of noise mapping, based on noise source model and propagation simulations, was developed and employed in the system. Dynamic estimation of noise source parameters utilized in the system is introduced. The details of implementation of noise map computation and visualization are presented. Advances introduced by the developed solution in the continuous noise monitoring and acoustic maps creation is in focus. The results of measurements and simulations performed by the system prototype are depicted. Noise measurements results gathered by system and created acoustic maps are compared with some other solutions in order to investigate accuracy

Validations and improvements of airfoil trailing‐edge noise prediction models using detailed experimental data

ABSTRACTThis paper describes an extensive assessment and a step by step validation of different turbulent boundary‐layer trailing‐edge noise prediction schemes developed within the European Union funded wind energy project UpWind. To validate prediction models, measurements of turbulent boundary‐layer properties such as two‐point turbulent velocity correlations, the spectra of the associated wall pressure fluctuations and the emitted trailing‐edge far‐field noise were performed in the laminar wind tunnel of the Institute of Aerodynamics and Gas Dynamics, University of Stuttgart. The measurements were carried out for a NACA 643‐418 airfoil, at Re = 2.5 ×106, angle of attack of −6° to 6°. Numerical results of different prediction schemes are extensively validated and discussed elaborately. The investigations on the TNO‐Blake noise prediction model show that the numerical wall pressure fluctuation and far‐field radiated noise models capture well the measured peak amplitude level as well as the peak position if the turbulence noise source parameters are estimated properly including turbulence anisotropy effects. Large eddy simulation based computational aeroacoustic computations show good agreements with measurements in the frequency region higher than 1 kHz, whereas they over‐predict the sound pressure level in the low‐frequency region. Copyright © 2011 John Wiley & Sons, Ltd.

Non-cavitating propeller noise source inversion

Ship's propeller cavitation generates major inboard noise and vibration over the aft body surface of a ship. During the last decade, cavitation-induced hull pressure forces have been reduced considerably leading to reduced noise and vibration levels owing to cavitation, in which case the non-cavitating components of propeller excitations have to be considered: pressure fluctuations due to blade loading and blade thickness. In this work, an algorithm to invert for the non-cavitating propeller noise source parameters based on the experimental data in a cavitation tunnel is shown. The fluctuating hull pressure is estimated by forward modeling based on acoustic boundary element method (BEM). The propeller blade loading and thickness noise sources are modeled using rings of dipoles and quadrupoles, respectively. The inversion for these pseudo sources are carried out by matching the data obtained from a cavitation tunnel experiment, where several hydrophone are flush mounted on the ship's surface near the propeller. Proper inversion results are obtained when six or more dipole and quadrupole rings are placed at each blade. Using the inverted source parameters, hull pressures were estimated, which show good agreement with the experiment data.

Creating Acoustic Maps Employing Supercomputing Cluster

The implemented online urban noise pollution monitoring system is presented with regard to its conceptual assumptions and technical realization. A concept of the noise source parameters dynamic assessment is introduced. The idea of noise modeling, based on noise emission characteristics and emission simulations, was developed and practically utilized in the system. Furthermore, the working system architecture and the data acquisition scheme are described. The method for increasing the speed of noise map calculation employing a supercomputer is explained. The practical implementation of noise maps generation and visualization system is presented, together with introduced improvements in the domain of continuous noise monitoring and acoustic maps creation. Some results of tests performed using the system prototype are shown. The main focus is put on assessing the efficiency of the acoustic maps created with the discussed system, in comparison to results obtained with traditional methods.

Comprehensive evaluation and assessment of trailing edge noise prediction based on dedicated measurements

An extensive assessment and step by step validation of turbulent boundary-layer trailing-edge interaction (TBL-TE) prediction was conducted based on the boundary layer properties calculated by three different aerodynamics methods, XFOIL, Wilcox EDDYBL and the RANS solver FLOWer. For this purpose detailed measurements of turbulent boundary-layer properties like two-point turbulent velocity correlations, the spectrum of the associated wall pressure fluctuations (WPFs) and the emitted trailing-edge noise have been performed in the Laminar Wind Tunnel (LWT). The measurements were performed for the NACA 0012 airfoil. Most of the investigated cases show that the numerical WPF and far-field radiated noise models capture the measured peak amplitude level as well as the peak position remarkably well, if the turbulence noise source parameters are estimated properly including turbulence anisotropy effects.

Improved Microwave Noise Performance by SiN Passivation in AlGaN/GaN HEMTs on Si

Effects of silicon nitride (SiN) surface passivation by plasma enhanced chemical vapor deposition (PECVD) on microwave noise characteristics of AlGaN/GaN HEMTs on high-resistivity silicon (HR-Si) substrate have been investigated. About 25% improvement in the minimum noise figure (NF min) (0.52 dB, from 2.03 dB to 1.51 dB) and 10% in the associate gain (G a) (1.0 dB, from 10.3 dB to 11.3 dB) were observed after passivation. The equivalent circuit parameters and noise source parameters (including channel noise coefficient (P), gate noise coefficient (R), and their correlation coefficient (C)) were extracted. P, R and C all increased after passivation and the increase of C contributes to the decrease of the noise figure. It was found that the improved microwave small signal and noise performance is mainly due to the increase of the intrinsic transconductance (g m0) and the decrease of the extrinsic source resistance (R s).

Rapid assessment of undersea ambient noise

Undersea ambient noise is a critical parameter in determining the performance of passive sonar systems, and sometimes active systems. There are many properties of the ambient noise that must be considered in a rapid ambient noise field assessment, including mean and percentile levels as a function of frequency, temporal and spatial variation, vertical and horizontal directionality, and depth dependence. In addition, rapid interpretation and extrapolation of the measured and analyzed ambient noise results require a credible onboard ambient noise prediction model and collateral noise model input measurements of oceanographic, acoustic, meteorological, and noise source parameters, e.g., sea and swell height, wind speed, and the positions, speeds, courses, and lengths of near and distant ships. Finally, turnkey data processing programs and time proven analysis procedures must be utilized with onboard graphics and word processing capabilities to generate the assessment document onboard in final form. The methods and techniques used by the SACLANT Undersea Research Centre (SACLANTCEN) and the Naval Research Laboratory (NRL) for rapid onboard assessment of the ambient noise are presented and discussed. [Work supported by Project 01 of SACLANTCEN and the Office of Naval Research through the management of the WISPR Filter Development and Evaluation Project by NRL.]

Two-polarity pulse noise in reverse biased degraded p–n junctions

The experimental results and analysis of pulse noise in degraded field plated PIN photodiodes are presented. A method for calculation of noise source parameters based on noise measurements in the time and the frequency domain is proposed.

Determination of the RF-noise source parameters in AlInAs/GaInAs-HEMT heterostructures based on measured noise temperature dependence against electric field

The noise temperature dependence on the electric field in an AlInAs/GaInAs-HEMT heterostructure has been measured. It was found that the dependence of the noise temperature on the electric field in GaAs-MESFETs and in AlInAs/GaInAs-HEMTs is remarkably different. For this reason a different model must be used for AlInAs/GaInAs-HEMTs. Based on the measured noise temperature dependence on the electric field, an analytic noise model for the AlInAs/GaInAs HEMT has been developed. The noise source parameters were calculated and compared with extracted noise source parameters from noise measurements.

Determination of a Low Frequency Noise Source's Parameters by a Space Intensity Sensor

The aim of this paper is to present the basic equations and the first results of an experimental investigation using the space intensity sensor. We offer a multi-element acoustic sensor that gives the opportunity to find the source's parameters (distance between the observer and the source, direction to the source, power of its radiation, its multipole type). It is very important for the diagnosis of natural low frequency sources. The results of the measurements of the sound multipole source's parameters are presented. The test's experimental data correspond well to the real controlled parameters.