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QC 351 A7 no. 65 / The significance of signal-dependent noise is discussed. Particular emphasis is placed on the type of multiplicative noise present in the density variations in a photographic emulsion. A theoretical treatment of the effect of multiplicative noise on signal detection and signal discrimination problems is presented. Optimum test statistics are derived for processing a sampled message to detect the presence of a known signal. Multiplicative noise described by Poisson and Gaussian statistics is considered. The expressions are extended to include the two-signal discrimination problem. Two-dimensional signal fields in the presence of multiplicative noise are simulated in a computer and processed for optimum signal detection according to the two derived methods. These results are compared to the results of processing based on the assumption of stationary noise statistics. This comparison reveals that modest improvements (20% to 30% reduction in false alarm rate) are obtained when the signal-dependent nature of the noise statistics is considered. The effects of signal-to-noise ratio, signal structure, and changing background level are also investigated. An example of optimum signal discrimination using circles and squares as signals in multiplicative noise is reported. An improvement in the percentage of correctly identified signals is again observed when the proper test statistic is used. Two examples of signal filtering in the presence of signal-dependent noise are included. The first concerns the processing of a real star field to determine the location of weak stars. The second is an illustration of the signal information contained in the noise spectrum of a message recorded on a common photographic film.

Cette étude porte sur le développement d’une méthodologie de calcul pour évaluer les effets d’installation. Ce phénomène, qui représente le bruit d’interaction entre un jet double flux et un profil, constitue un problème modèle pour l’étude du bruit de jet installé en aéronautique. L’écoulement moyen est déterminé à partir de la résolution des équations de Navier-Stokes moyennées et du modèle de turbulence k - ω BSL de Menter. Lorsque le jet est isolé, il est possible ensuite d’utiliser le modèle de Tam & Auriault. Dans des configurations plus complexes, comme l’interaction jet-voilure considérée ici, la formulation statistique des termes sources de ce modèle est retenue à la place du modèle complet. Un propagateur acoustique, basé sur les équations d’Euler linéarisées, est utilisé pour compléter la modélisation. Dans un premier temps, une tuyère double flux avec plug est simulée et les résultats obtenus sont comparés aux données d’essais dans le but de valider la simulation numérique. De bons résultats sont obtenus. La même étude est ensuite réalisée sur une configuration installée, prenant en compte la même tuyère installée sous un profil. La simplicité de la configuration se justifie par le fait qu’il s’agit de développer une méthodologie de calcul permettant d’avoir un effet qualitatif de l’installation sur le développement du jet. En comparant les résultats aérodynamiques avec ceux obtenus numériquement pour la tuyère isolée, l’impact du profil sur le jet est mis en évidence au travers de la déviation du jet vers le profil et d’un déficit de l’énergie cinétique turbulente. La dernière étape consiste à caractériser l’impact de ces modifications sur les sources de bruit. Pour cela, le logiciel de propagation industriel Actran DGM est utilisé. Les sources calculées statistiquement par le modèle de Tam & Auriault sont introduites dans les équations d’Euler linéarisées. En première approche pour mettre en œuvre la méthodologie, les sources de bruit de jet sont assimilées à une distribution de monopoles équivalents. Cette modélisation permet de mettre en évidence les effets de diffraction et de masquage de l’onde causés par le profil. Le rayonnement en champ lointain est quant à lui obtenu avec la méthode intégrale de Ffowcs-Williams & Hawkings. / Excess noise induced by installation effects is numerically investigated in this work. Interaction noise between a turbofan jet engine and an airfoil is a simplified but relevant problem to address installed jet noise in aeronautics. The mean flow is determined from Reynolds-Averaged Navier-Stokes equations, using Menter k - ω BSL turbulence model. With jet only, fine scale turbulence model of Tam & Auriault can be used directly for jet noise prediction. To assess jet-wing interaction in industrial configuration, the statistical formulation of the source terms is retained from this stochastic model, and the acoustic propagation is performed using linearised Euler equations. A dual stream jet is firstly computed and the results are compared to available data in order to validate the numerical simulation. Satisfactory results are obtained. The same study is then performed on an installed configuration, taking into account the same nozzle installed under a profile. This first configuration is is used to develop a methodology of calculation by having a qualitative effect of the installation on the jet behaviour. By comparing the aerodynamic results with those obtained numerically for the isolated nozzle, the impact of the jet profile is highlighted through the jet deflection and a modification of the turbulent kinetic energy field. The last step is to characterize the impact of these modifications on the noise sources. For this, the industrial propagation software Actran DGM is used. The statistical formulation of the source calculated by Tam & Auriault model is introduced into the linearised Euler equations. As a first step, the jet sources are defined as a distribution of equivalent monopoles. This modeling allows highlighting the effects of diffraction and the masking effects caused by the profile. The radiation in the far field is obtained with the integral method of Ffowcs-Williams & Hawkings.

This thesis has described a Reynolds Averaged Navier Stokes approach to modeling turbulence in the wake of a cylinder and airfoil. The mean flow, cross stresses, and two-point space time correlation structure was analyzed for an untripped cylinder with a Reynolds number based on the cylinder diameter and freestream velocity of 60,000. The same features were also analyzed using this approach for an untripped NACA 0012 airfoil with a Reynolds number based on the airfoil chord and freestream velocity of 328,000. These simulation results were compared to experimental and newly developed models for validation. The ultimate goal of this present study was to create the two-point space time correlation function of a cylinder and airfoil wake using RANS calculations which contributes to a larger study where the sound radiated by an open rotor due to ingestion of turbulence. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Au, Wai Hong. / Thesis submitted in: December 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 96-103). / Abstracts in English and Chinese; appendix in Chinese. / LIST OF TABLE --- p.I / LIST OF FIGURES --- p.II / LIST OF ABBREVIATIONS --- p.IV / Chapter CHAPTER ONE --- 1 INTRODUCTION --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research Background --- p.1 / Chapter 1.3 --- Objectives of The Study --- p.5 / Chapter 1.4 --- The Rail Project of This Study --- p.5 / Chapter 1.5 --- Significance of The Study --- p.9 / Chapter 1.6 --- Outline of Thesis --- p.10 / Chapter CHAPTER TWO --- LITERATURE REVIEW --- p.11 / Chapter 2.1. --- Introduction --- p.11 / Chapter 2.2. --- Human Response in a Steady Traffic Noise Environment --- p.12 / Chapter 2.3. --- Human Response in an Environment with Sudden Change of Traffic Noise --- p.13 / Chapter 2.4. --- Differential Human Response to Road and Rail Noise --- p.15 / Chapter 2.5. --- Factors Affecting Human Response --- p.16 / Chapter 2.6. --- Path Analysis and Human Response to Traffic Noise --- p.18 / Chapter 2.7. --- Conclusion --- p.20 / Chapter CHAPTER THREE --- METHODOLOGY --- p.21 / Chapter 3.1 --- Introduction --- p.21 / Chapter 3.2 --- Research Design --- p.22 / Chapter 3.3 --- Assessing the Acoustic Impacts of Railway Development --- p.23 / Chapter 3.4 --- Assessing the Acoustic Impacts of MOSR --- p.28 / Chapter 3.4.1 --- Noise mapping --- p.28 / Chapter 3.4.2 --- On-site noise measurement --- p.32 / Chapter 3.5 --- Assessing the Changes in Human Response --- p.35 / Chapter 3.5.1 --- Questionnaire design --- p.36 / Chapter 3.5.2 --- Time Schedule of the questionnaire survey --- p.37 / Chapter 3.5.3 --- Statistical analysis --- p.38 / Chapter CHAPTER FOUR --- ACOUSTIC IMPACTS OF THE MA ON SHAN RAIL --- p.41 / Chapter 4.1 --- Introduction --- p.41 / Chapter 4.2 --- Traffic Changes Over Time After the Operation ofMOSR --- p.41 / Chapter 4.3 --- "Acoustic Environment Before, Right After and 1 Year After MOSR Opening" --- p.43 / Chapter 4.3.1 --- Acoustic environment before MOSR opening --- p.44 / Chapter 4.3.2 --- Acoustic environment right after MOSR opening --- p.45 / Chapter 4.3.3 --- Acoustic environment 1 year after MOSR opening --- p.50 / Chapter 4.4 --- Conclusion --- p.54 / Chapter CHAPTER FIVE --- HUMAN RESPONSE TO THE CHANGING ACOUSTIC ENVIRONMENT --- p.57 / Chapter 5.1 --- Changes of Annoyance Levels in an Environment with Increase of Noise Exposure Level --- p.58 / Chapter 5.2 --- Relationship Between Noise Controlling Factors and Annoyance by Correlation Analysis --- p.59 / Chapter 5.3 --- Unraveling the Relationship between Noise Controlling Factors and Annoyance by Regression Analysis --- p.66 / Chapter 5.3.1 --- Relationship between Acoustic Factors and Human Annoyance Reactions --- p.68 / Chapter 5.3.2 --- Relationship between non-acoustic factor in affecting human annoyance reactions --- p.70 / Chapter 5.4 --- Exploring the Causal Relationship between Annoyance and Its Controlling Factors by Path Analysis --- p.74 / Chapter 5.4.1 --- Formation of path model --- p.75 / Chapter 5.4.2 --- Casual relationship between annoyance and various controlling factors --- p.79 / Chapter 5.5 --- Conclusions --- p.85 / Chapter CHAPTER SIX --- CONCLUSION --- p.88 / Chapter 6.1 --- Introduction --- p.88 / Chapter 6.2 --- Summary of Findings --- p.89 / Chapter 6.3 --- Discussion of Findings --- p.92 / Chapter 6.3.1 --- Scientific understanding of noise-annoyance relationships --- p.92 / Chapter 6.3.2 --- Environmental management --- p.94 / Chapter 6.4 --- Limitations and Future Studies --- p.95 / REFERENCE LIST --- p.96 / APPENDIX --- p.104

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1976. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references (leaf 41). / Carl A. Wales. / B.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 346-350. / by David Herbert Munro. / Ph.D.

Este projeto de pesquisa pretende contribuir para o tema da acústica do ambiente externo às igrejas, fornecendo um panorama em linhas gerais da natureza e magnitude das ocorrências sonoras externas às igrejas de uma área de amostragem constituída por 12 igrejas situadas em região urbana na cidade de São Paulo. A partir de dados coletados do entorno, das tipologias, dos resultados das medições sonoras e da aplicação de questionários, a pesquisa pretende compreender melhor as causas e os efeitos das fontes de ruído na vizinhança, bem como a de recomendar meios de prevenção dos problemas, tanto nos projetos de novas edificações como na escolha e adaptação de edificações existentes para a finalidade do culto religioso. / This research project aims to contribute to the acoustic theme of the external environment to the churches, providing an overview in general terms the nature and magnitude of external sound events to the churches of a sampling area consists of 12 churches located in urban areas in the city of São Paulo. The data collected from the field survey, made available around the information and typology of the churches and the comparison of results of noise measurements,the research seeks to analyze the causes and effects of noise sources in the vicinity, as well as recommend means of preventing problems, both in the projects of new buildings in the choice and adaptation of existing buildings for the purpose of religious worship.

Este projeto de pesquisa pretende contribuir para o tema da acústica do ambiente externo às igrejas, fornecendo um panorama em linhas gerais da natureza e magnitude das ocorrências sonoras externas às igrejas de uma área de amostragem constituída por 12 igrejas situadas em região urbana na cidade de São Paulo. A partir de dados coletados do entorno, das tipologias, dos resultados das medições sonoras e da aplicação de questionários, a pesquisa pretende compreender melhor as causas e os efeitos das fontes de ruído na vizinhança, bem como a de recomendar meios de prevenção dos problemas, tanto nos projetos de novas edificações como na escolha e adaptação de edificações existentes para a finalidade do culto religioso. / This research project aims to contribute to the acoustic theme of the external environment to the churches, providing an overview in general terms the nature and magnitude of external sound events to the churches of a sampling area consists of 12 churches located in urban areas in the city of São Paulo. The data collected from the field survey, made available around the information and typology of the churches and the comparison of results of noise measurements,the research seeks to analyze the causes and effects of noise sources in the vicinity, as well as recommend means of preventing problems, both in the projects of new buildings in the choice and adaptation of existing buildings for the purpose of religious worship.

Electrochemical noise refers to the spontaneous fluctuations in potential and current that can be observed on a corroding metal. The use of electrochemical noise for obtaining information on the corrosion process generates much interest in research fields. One important application is the measurement of corrosion rate. This can be achieved using the electrochemical noise of a pair of electrically coupled corroding metals to obtain an estimate of electrochemical impedance - an abstract quantity that reflects various aspects of the corrosion process.There are a number of problems associated with estimation of impedance information from the electrochemical noise data, particularly regarding data pre-treatment, accuracy and precision. In addition, the present methods are incomplete: current literature does not offer information regarding the phase of the impedance; and assumptions regarding symmetry of an electrode pair cannot be tested without additional measurements.The thesis addresses the above mentioned problems. Specifically,analysis of the impedance estimation process is given to determine how precision can be affected by various factors;a novel signal processing technique is described that is shown to yield a local optimum precision;the application of the proposed signal processing to time varying systems is demonstrated by use of a time varying, frequency dependent impedance estimate;a technique for recovering phase information, given certain conditions, is suggested so that Nyquist impedance diagrams can be constructed; anda technique for testing the symmetry of a coupled pair of corroding metals is described.An integral part of electrochemical noise analysis is the software used for numerical computation. The Matlab package from MathWorks inc. provides an extensible platform for electrochemical noise analysis. Matlab code is provided in Appendix A to implement ++ / much of the theory discussed in the thesis.Impedance analysis and many other electrochemical corrosion monitoring techniques are primarily used for uniform corrosion, where the corrosion patterns occur uniformly over the exposed surface. In order to map localised corrosion, where the corrosion is typically concentrated within a small area, a wire beam electrode can be used. A wire beam electrode is a surface that is divided into a matrix of mini-electrodes so that the corrosion rate at different points can be monitored. However, manual connection of each mini-electrode to the measurement device can prove cumbersome. The final chapter of this thesis describes the design and testing of specialised multiplexing hardware to automate the process.In general, the thesis shows that by careful conditioning of the electrochemical noise prior to analysis, many of the problems with the technique of impedance estimation from the electrochemical noise data can be overcome. It is shown that the electrochemical noise impedance estimation can be extended to encompass a time varying, frequency dependent quantity for studying dynamic systems; that phase information can be recovered from electrochemical noise for the purpose of constructing Nyquist impedance diagrams; and that asymmetric electrodes can be detected without requiring additional measurements.