Railway induced ground-borne vibration is among the most common and widespread sources of perceptible environmental vibration, adversely impacting on human activity and the operation of sensitive equipment. The rising demand for building new railway lines or upgrading existing lines in order to meet increasing traffic flows has furthered the need for adequate vibration assessment tools during scheme planning and design. In recent years many studies of rail and ground dynamics have produced many vibration prediction techniques which have given rise to a variety of procedures for estimating rail-induced vibration on adjacent buildings. Each method shows potential for application at different levels of complexity and at different stages of a scheme. However, for the majority of the procedures significant challenges arise in obtaining the required input data, which can compromise their routine use in Environmental Impact Assessment (EIA). Moreover, as the majority of prediction procedures do not provide levels of uncertainty (i.e. expected spread of data), little is available on their effectiveness. Additionally, some procedures are restricted in that they require specific modelling approaches or proprietary software. Therefore, from an industrial point of view there is a need for a robust and flexible rail-induced vibration EIA procedure that can be routinely used with a degree of confidence. Based on an existing framework for assessing rail-induced vibration offered by the USA department of transportation (FTA) this project investigates, revises and establishes an empirical procedure capable of predicting rail-induced vibration in nearby buildings that can be routinely applied by the sponsoring company. Special attention is given to the degree of variability inherent to rail-induced vibration prediction, bringing forward the degrees of uncertainty, at all levels (i.e. measuring, analysis and scenario characterisation) that may impact on the procedure performance. The research shows a diminishing confidence when predicting rail-induced absolute vibration levels. It was found that ground-to-transducer coupling method, which is a critical step for acquiring data for characterising the ground, can impact on the results by as much as 10 dB. The ground decay rate, when derived through transfer functions, also showed to vary significantly in accordance to the assessment approach. Here it is shown the extent to which track conditions, which are difficult to account for, can affect predictions; variability in vibration levels of up to 10 dB, at some frequency bands, was found to occur simply due to track issues. The thesis offers general curves that represent modern UK buildings; however, a 15 dB variation should be expected. For urban areas, where the ground structure is significantly heterogeneous, the thesis proposes an empirical modelling technique capable of shortening the FTA procedure, whilst maintain the uncertainty levels within limits. Based on the finding and acknowledging the inherent degree of variability mentioned above, this study proposes a resilient empirical vibration analysis model, where its flexibility is established by balancing the significance of each modelling component with the uncertainty levels likely to arise due to randomness in the system.

High quality noise and vibration measurements outside of a laboratory environment on real life structures and applications are not trivial. True boundary and operating conditions enforce unique challenges on the measurements. Measurements in hazardous situations such as high magnetic fields, and high temperature environments, etc., where ordinary measurement equipment and methods may not be employed, require further precautions. Post measurements objectives such as analysis, design and strategic decisions, e.g., control, rely heavily on the quality and integrity of the measurements (data). The quality of the experimental data is highly correlated with the on-field expertise. Practical or hands-on experience with measurements can be imparted to prospective students, researchers and technicians in the form of laboratory experiments involving real equipment and practical applications. However, achieving expertise in the field of sound and vibration measurements in general and their active control in particular is a time consuming and expensive process. Consequently most institutions can only afford a single setup, resulting in the compromise of the quality of expertise. In this thesis, the challenges in the field of sound and vibration measurements in high magnetic field are addressed. The analysis and measurement of vibration transferred from an operational magnetic resonance imaging (MRI) scanner to adjacent floors is taken as an example. Improvised experimental measurement methods and custom-made frequency analysis techniques are proposed in order to address the challenges and study the vibration transfer. The methods may be extended to other operational industrial machinery and hazardous environments. To encourage and develop expertise in the field of acoustic/vibration measurements and active noise control on practical test beds, remotely controlled laboratory setups are introduced. The developed laboratory setup, which is accessed and controlled via the Internet, is the first of its kind in the active noise control and acoustic measurements area. The laboratory setup can be shared and utilized 24/7 globally, thus reducing the associated costs and eliminating time restrictions.

Fully turbulent inflow past symmetrically located side branches mounted in a duct can give rise to pronounced flow oscillations due to coupling between separated shear layers and standing acoustic waves. Experimental investigation of acoustically-coupled flows was conducted using digital particle image velocimetry (DPIV) in conjunction with unsteady pressure measurements. Global instantaneous, phase- and time-averaged flow images, as well as turbulence statistics, were evaluated to provide insight into the flow physics during flow tone generation. Onset of the locked-on resonant states was characterized in terms of the acoustic pressure amplitude, frequency and the quality factor of the resonant pressure peak. Structure of the acoustic noise source is characterized in terms of patterns of generated acoustic power. In contrast to earlier work, the present study represents the first application of vortex sound theory in conjunction with global quantitative flow imaging and numerical simulation of the 2D acoustic field. In addition to the basic side branch configuration, the effects of bluff rectangular splitter plates located along the centerline of the main duct was investigated. The first mode of the shear layer oscillation was inhibited by the presence of plates, which resulted in substantial reduction of the amplitude of acoustic pulsations and the strength of the acoustic source. These results can lead to the development of improved control strategies for coaxial side branch resonators. Motivation for the second part of this study stems from the paper manufacturing industry, where air clamp devices utilize high-speed jets to position paper sheets with respect to other equipment. Thus, vibration of the paper sheet and turbulent flow that emerged from a planar curved nozzle between a flexible wall and a solid surface containing a backward-facing step (BFS) were investigated using high-speed photography and DPIV, respectively. The emphasis was on the characterization of the flow physics in the air clamp device, as well as of the shape of the paper sheet. For the control case, that involved a solid wall with a geometry that represented the time-averaged paper profile, hydrodynamic oscillation frequencies were characterized using unsteady pressure measurements. Experimentally obtained frequencies of the paper sheet vibration were compared to the hydrodynamic frequencies corresponding to the oscillations of the shear layer downstream of the BFS.

This thesis is part of the on going work at BTH (Blekinge Technical University) to develop a remote lab for Sound and Vibration Experiments. The aim of this undertaking is to develop a Spectrum Analyzer that can simultaneously take inputs from 10 sensors and be able to measure the Power Spectral Density, Cross correlation, Frequency Response Functions (FRF) and coherence. The Interface and analysis algorithms are developed inLabview programming language. The thesis starts by introducing the overall aim of the project and its scope, the place of this particular thesis in the whole picture and the algorithms used for analysis are introduced. In the second part of the thesis the development of the software is explained and the main aim is to thoroughly document the software. This part of the thesis explains Labview programming concepts in detail to make it easier for other students who want to undertake theses to continue this work and who may not have experience of Labview programming.Two versions of the spectrum analyzer were developed. The third part explains theexperimental set up and results obtained and compares measurements to those obtained using other spectrum analyzers. An accurate Spectrum Analyzer Virtual Instrument has been developed and tested during this thesis project and it can be used as a component of the proposed Sound and vibration analysis laboratory and also for general Spectral Analysis tasks. / Good guide to learn Labview and sound and vibration analysis.. / fkul08@gmail.com Is my email and i can be contacted via messenger usually at farooq_kifayat@hotmail.com And i can also be contacted via skype using farooqkifayat as my name. I move around a lot so i have no permanent address that stays longer than half a year .

This master’s thesis deals with the computational simulation of low-frequency noise inside the cabin of small commercial airplane VUT 100 Cobra. For this low-frequncy range deterministic methods: Final Element Method (FEM) and Boundary Element Method (BEM) are used for simulation of the dynamic behaviour of the object. FEM has been used to compute eigenmodes and eigenfrequences of the structure of the aeroplane cabin and of the acoustic space inside cabin. Then response to harmonic excitation of engine represented by unit forces in place of contact has been computed. Obtained velocities on the surface of the cabin are then used as the basis for the noise calculation inside the cabin using BEM. After that effect of some construction modifications on sound level inside cabin are evaluated by computational modelling.

Experimental validations are widely used for studying dynamic structural behaviors and these studies involve defining the structures completely as being used in real time. While in numerical simulations such detailed features are not specified to ease the computation, thereby deviating from accurate results. Hence experimental validations are more desired in product developments process. Applications of experimental verification for noise and vibration (referred to as NVH inautomotive industry) are expanding over the last few decades. Researchers are exploring ways to predict the responses on the new receiver using receiver independent forces, which led to evolution of component based TPA (Transfer Path Analysis) concept. The Component based TPA concept is an important development in automotive industry. It allows the auto manufacturers to make use of their available subsystems (like motor or a gearbox) in their newly developing vehicles. This has been made possible by defining the dynamic forces exerted by the source independent of receiving structure, which are then used to predict the responses on the new receiver. Evaluation of such receiver independent forces allows measurements to be made in a test rig rather than in the vehicle. This indeed helps in better communication between different departments or between suppliers and vehicle manufacturers, saves design iterations and time, and would help vehicle manufactures to predict the vehicle structural behaviors much before the first prototype is made. The method is based on the international standard ISO 20270:2019 (en) Acoustics – Characterization of sources of structure-borne sound and vibration – indirect measurement of blocked forces. The thesis is based on evaluating the source characterized forces that are used for predicting responses on a new receiving structure. For this, different methods in TPA are explored and for the rear drive unit application, in-situ method is chosen. The source characterized forces also termed as blocked forces are computed in different test set up and a validation check is performed. The obtained results are also compared with FEM and useful conclusions are drawn. And finally contact forces evaluated by integrating the subsystems are compared to the contact forces derived from the source characterized forces. / Experimentell verifiering av dynamiska krafter och vibrationer som uppkommer i fordon innebär mätning av tids-, frekvens- och/eller varvtalsberoende kvantiteter. Numeriska beräkningar har utvecklats till en hög nivå, men kan ännu inte beskriva alla förlopp och detaljer som förekommer i de verkliga processerna. På grund av detta krävs det fortfarande mätningar som en del av produktionsutvecklingen. Valideringsmetoder för ljud och vibrationer har utvecklats mycket desenaste decennierna, och ett mål har varit att utveckla mätmetoder där de uppmätta krafterna från en komponent som bidrar till buller kan mätas på ett sätt som inte beror på den testrigg eller det fordon den mäts i. Komponentbaserad TPA Transfer Path Analysis är en analysmetod som är viktig inom fordonsindustrin. Den gör det möjligt för en tillverkare att använda modeller av existerande komponenter (t.ex. motorer eller växellådor) i modeller för nya fordon. En grundläggande förutsättning är att de krafter som mäts är oberoende av den mottagande strukturen, det vill säga fordonet. Om krafterna är oberoende av strukturen där de mäts innebär det att komponenten kan mätas i en test rigg på ett annat ställe (till exempel hos en underleverantör) och att tillgång till fordon inte krävs för karaktäriseringen. Det underlättar kommunikationen mellan olika delar av organisationen och mellan underleveratörer och tillverkare och bidrar till att prediktera ljud och vibrationer innan den första prototypen är tillgänglig. Den föreslagna metoden är baserad på den internationella normen ISO 20270:2019 (en) Acoustics – Characterization of sources of structure-borne sound and vibration – indirect measurement of blocked forces. Examensarbetet handlar om att utveckla en mätmetod för att kunna ta fram krafter genererade av komponenter som är oberoende av testriggens egenskaper. De framtagna krafterna kan då användas i en virtuell fordonsmodell för att se ljud och vibrationsbidragen på fordonsnivå. Källan som har studerats är en slutväxel (rear drive unit) för fyrhjulsdrift i bil. Flera olikametoder för TPA har undersöks, och för karaktärisering av slutväxeln har in-situ metoden valts. Krafter som är oberoende av den mottagande strukturen kallas även ‘blocked forces’. Krafterna beräknas baserat på resultaten från flera olika delmätningar. Validering och även jämförelse medFEM beräkningar har gjorts liksom jämförelser mellan mätningar på enbart komponenten och av hela systemet.