Structures of machinery with practical importance, such as home appliances or transportation vehicles, can be considered as acoustically coupled spaces surrounded by elastic enclosures. When the structures of machinery are excited mechanically by means of prime movers incorporated into these structures through some elastic connections, generation of noise becomes an inevitable by-product. For noise control engineering purposes, a thorough understanding of emission, transmission and radiation of sound from structure is required prior to a possible and practical modeling of noise transfer mechanisms. Finally, development of a model for complete noise generation and transfer mechanisms is needed which is essential for the abatement of annoying sound generation. In this study, an experimental and analytical (finite element) methodology for the modal analysis of acoustical cavities is developed, and successfully applied to a case study. The acoustical transmission problem of the structure is investigated via vector intensity analysis. Results of this investigation are used for a noise path qualification, whereas the transfer functions between sources of noise and some relevant receiving points are obtained by use of vibro-acoustic reciprocity principle. The concept of transfer path analysis is investigated by using the multi input, multi output linear system theory for vibro-acoustic modeling of machinery structures. Finally, resolution and ranking of noise sources and transfer paths are accomplished via spectral correlation methodologies developed. The methodology can be extended to any system with linear, time invariant parameters, where principles of superposition and reciprocity are applicable.

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Over the last years, due to the development of quieter engines and drivetrains, the importance of addressing the vehicle wind noise problem has significantly increased.In this thesis work, several existing Transfer Path Analysis methods have been applied on an experimental database acquired during a wind tunnel test on a passenger car with the objective of analyzing the distribution of the wind noise sources and their contribution to the target microphones located inside the vehicle. A major challenge for the Transfer Path Analysis (TPA) consists of the high complexity of the aerodynamic sources exciting the structure. Moreover, the existence of multiple incoherent source phenomena, and the presence of distributed coherent source regions of different correlation scales make the analysis very complex.The thesis work provides a solid and comprehensive analysis of the results obtained by different methods. The outcomes can be potentially useful for optimizing the vehicle NVH performance in future practical cases. / Under de senaste åren har vikten av att arbeta med vägfordons problem med aerodynamisk ljudgenerering ökat avsevärt på grund av utvecklingen av tystare motorer och drivlinor. I det här projektet har flera existerande metoder för Transfer Path Analysis (TPA) tillämpats på en databas med experimentella data som samlats in vid vindtunneltest på en personbil, med målet att analysera fördelningen av källorna orsakade av vindbruset och deras påverkan på ljudnivån vid de uppsatta målmikrofonerna inuti fordonet. En stor utmaning för TPA är den höga komplexiteten hos de aerodynamiska källorna som exciterar strukturen. Vidare gör förekomsten av flera okorrelerade källor, och närvaron av distribuerade koherenta källregioner med olika korrelationsskalor, analysen mycket komplex. Arbetet presenterar en solid och omfattande analys av resultat som erhållits med olika metoder. Resultaten är potentiellt användbara för att optimera fordonets NVH-prestanda i praktiktiken i framtiden.

The field of modal testing and analysis is currently facing a surge of interest in error modelling. Several errors which occur during testing campaigns are modelled analytically or numerically and propagated to various system coupling and interface reduction routines effectively. This study aims to propagate human errors, like position measurement errors and orientation measurement errors, and random noise-based errors in the measured Frequency Response Functions(FRFs) to the interface reduction algorithm called Virtual Point Transformation(VPT) and later to a substructure coupling method called Frequency-Based Substructuring(FBS). These methods form the cornerstone for Transfer Path Analsysis (TPA). Furthermore, common sources of error like sensor mass loading effect and sensor misalignment have also been investigated. Lastly, a new method to calculate the sensor positions and orientations after a measurement has been devised based on rigid body properties of the system and from the applied force characteristics. The error propagation was performed using a computationally efficient, moment method of the first order and later validated using Monte-Carlo simulations. The results show that the orientation measurement error is the most significant followed by FRF error and position measurement error. The mass loading effect is compensated using the Structural Modification Using Response Functions (SMURF) method and the sensor misalignment is corrected using coordinate transformation. The sensor positions and orientations are accurately estimated from rigid body properties and applied force characteristics; individually using matrix algebra and simultaneously using an optimization-based non-linear least squares solver. / För närvarande ser vi ett ökat intresse för felmodellering inom området modal provning och analys. Flera fel som uppstår under testserier modelleras analytiskt eller numeriskt och propageras effektivt till olika systemkopplings- och gränssnittsreduktionsrutiner. Denna studie syftar till att hantera mänskliga fel, som positionsmätningsfel och orienteringsmätfel, och slumpmässiga brusbaserade fel i de uppmätta frekvensresponsfunktionerna (FRF) till den gränssnittsreduktionsalgoritm, som kallas ”Virtual Point Transformation” (VPT), och senare till en substrukturskopplingsmetod, som kallas FBS (Frequency-Based Substructuring). Dessa metoder utgör hörnstenen för ”Transfer Path Analsysis” (TPA). Dessutom har vanliga felkällor som sensormassbelastningseffekter och felorientering av sensorer undersökts. Slutligen har en ny metod för att beräkna sensorns positioner och riktningar, efter att mätning gjorts, baserat på systemets stelkroppsegenskaper och de applicerade krafterna. Felpropageringen estimerades med en beräkningseffektiv, momentmetod av första ordningen och validerades senare med Monte-Carlo-simuleringar. Resultaten visar att orienteringsmätfelet är den mest signifikanta felkällan följt av FRF-fel och positionsmätningsfel. Massbelastningseffekten kompenseras med hjälp av ”Structural Modification Using Response Functions” (SMURF) -metoden och sensorjusteringen korrigeras med hjälp av koordinatomvandling. Sensorpositionerna och positioner och orientering beräknas exakt från stelkroppsegenskaperna och de applicerade krafterna; individuellt med matrisalgebra och samtidigt med en optimeringsbaserad icke-linjär minsta kvadratlösare.

Vattenburen kollektivtrafik tenderar att ha längre bytessträckor än buss och spårtrafik. Då långa byten kräver mer av resenären är uppsatsens syfte att undersöka hur bytet till och från pendelbåtar kan se ut vid en för trafiken större bytespunkt. Därigenom kanske vi kan lära oss mer om resenärens informationsbehov vid byten över längre avstånd. Därtill har målet varit att presentera rekommendationer som kan stärka förutsättningarna för vattenburen kollektivtrafik, med särskilt fokus på bryggan (angöringspunkten) vid Klara Mälarstrand och den närliggande järnvägsstationen Stockholm Central. Arbetet har utförts i form av en fallstudie som undersökte platsen utifrån upplevd närhet och -tydlighet, med empiri bestående av egentagna bilder, kartor, avståndsmätningar samt dokument. Datainsamlingen pågick under lång tid, parallellt med Trafiknämndens egna utredningar av trafik till och från bryggan. Analysen visade att bryggan vid Klara Mälarstrand är bristfälligt integrerad med omgivande kollektivtrafik och att en tydlig vägledning saknas. I diskussionen förs ett resonemang om vikten av att entréer till kollektivtrafiken, exemplifierat av pendeltågens nya station Stockholm City, synliggör sin funktion även på långt håll. Resenärer bör även ges möjlighet att relatera längre bytessträckor till en tidsåtgång, liknande den ’uppskattad gåtid till gate’ som används på storflygplatser som Köpenhamns flygplats Kastrup. / Public transport on water tend to have longer transfer paths than bus and rail transport. As long transfers paths demands more from the passenger this thesis aims to investigate what a transfer to and from water buses may look like at a transfer point with public transport on water of major importance for a planned service in Stockholm, Sweden. Through that more knowledge about the information needs of passengers at transfers over longer distances might be gained. In addition the thesis aims to present recommendations which can strengthen the conditions for public transport on water, with a focus on the stop (quay) near the Stockholm Central station. The thesis has been carried out as a case study which examined the study area on the basis of perceived proximity and -legibility,with empirics consisting of images taken by the author, maps, distance measurements and documents. Data collection time has been long, in parallel with the Stockholm County Administrations (SLL) own investigations of the traffic. The analysis showed that the quay at Klara Mälarstrand has a lacking integration with surrounding public transport and that a clear wayfinding is missing. In the discussion an argument for the importance of legible entrances to public transport also at a distance is made, exemplified by the new Stockholm City commuter train station building. Also passengers at longer transfer paths needs to be able to relate the distance with the time to get there, similar to the ‘approximate walking time to gate’ used at major airports such as Copenhagen Airport, Kastrup in Denmark.

A análise de caminhos de transferência de energia (TPA na sigla em inglês para Transfer Path Analysis) corresponde a um grupo de métodos numérico/experimental para análise e solução de problemas vibro-acústicos de sistemas lineares invariantes no tempo, sendo seu principal campo de aplicação a indústria automotiva. A TPA é uma técnica que identifica as principais fontes de vibração e ruído, e os caminhos estruturais e acústicos pelos quais são transmitidas para determinados locais de interesse. Conhecendo as fontes de ruído e vibração e os caminhos de propagação é possível propor modificações eficientes em minimizar o ruído/vibração nas regiões de interesse, ou atribuir características desejáveis para tais componentes, envolvendo técnicas de controle passivo e ativo. Este trabalho apresenta um estudo numérico e experimental das técnicas de TPA, utilizando métodos diretos e inversos de determinação de forças operacionais. Estes estudos foram realizados em um mockup de um veículo, com o objetivo de determinar o caminho de maior contribuição para o ruído no interior do protótipo, e a partir deste resultado, propor um sistema de controle ativo para minimizar este ruído interno. / The Transfer Path Analysis (TPA) is a group of numerical/experimental tools for the analysis and troubleshooting of noise and vibration problems in linear time invariant vibroacoustic systems, being the automotive sector its major user. TPA consists of a numerical/experimental analysis that allows the identification of the main noise and vibration sources and the structural/acoustic transfer paths to the Target points. Based on the sources and paths, it is possible to propose modifications that efficiently minimize noise and vibration at the target positions. By means of active control it is possible to modify noise and vibration in order to change, rather than minimize noise and vibration, achieving certain design targets. This work presents a numerical and experimental study of TPA techniques, using direct and inverse operational loads determination methods. These studies were performed on a vehicle mockup, in order to determine the path of greatest contribution to the noise inside the prototype, and from this result, propose an active control system to minimize this internal noise.

A análise de caminhos de transferência de energia (TPA na sigla em inglês para Transfer Path Analysis) corresponde a um grupo de métodos numérico/experimental para análise e solução de problemas vibro-acústicos de sistemas lineares invariantes no tempo, sendo seu principal campo de aplicação a indústria automotiva. A TPA é uma técnica que identifica as principais fontes de vibração e ruído, e os caminhos estruturais e acústicos pelos quais são transmitidas para determinados locais de interesse. Conhecendo as fontes de ruído e vibração e os caminhos de propagação é possível propor modificações eficientes em minimizar o ruído/vibração nas regiões de interesse, ou atribuir características desejáveis para tais componentes, envolvendo técnicas de controle passivo e ativo. Este trabalho apresenta um estudo numérico e experimental das técnicas de TPA, utilizando métodos diretos e inversos de determinação de forças operacionais. Estes estudos foram realizados em um mockup de um veículo, com o objetivo de determinar o caminho de maior contribuição para o ruído no interior do protótipo, e a partir deste resultado, propor um sistema de controle ativo para minimizar este ruído interno. / The Transfer Path Analysis (TPA) is a group of numerical/experimental tools for the analysis and troubleshooting of noise and vibration problems in linear time invariant vibroacoustic systems, being the automotive sector its major user. TPA consists of a numerical/experimental analysis that allows the identification of the main noise and vibration sources and the structural/acoustic transfer paths to the Target points. Based on the sources and paths, it is possible to propose modifications that efficiently minimize noise and vibration at the target positions. By means of active control it is possible to modify noise and vibration in order to change, rather than minimize noise and vibration, achieving certain design targets. This work presents a numerical and experimental study of TPA techniques, using direct and inverse operational loads determination methods. These studies were performed on a vehicle mockup, in order to determine the path of greatest contribution to the noise inside the prototype, and from this result, propose an active control system to minimize this internal noise.

Even though there are no regulations on the interior noise level of passenger cars, it is a significant quality aspect both for customers and for car manufacturers. The reduction of many other car noise sources pushed tyre road noise to the forefront.What is more, well known phenomenon of the tyre acoustic cavity resonance (TCR), appearing around 225 Hz, makes the interior noise noticeably worse. Some techniques to mitigate this phenomenon right at the source are discussed in this thesis, however, these has not been adopted by the tyre nor car manufacturers yet.Therefore, there is a desire to minimise at least the transmission of the acoustic or vibration energy from the tyre to the compartment. This is where methods like TPA (Transfer Path Analysis) come into play.In this thesis, two different approaches to TPA are used to investigate transmission of the TCR energy.First, the coherence based road decomposition method is used to determine whether the TCR energy is transmitted by a structure-borne or an air-borne mechanism. The same method serves to identify if the TCR noise comes mainly from the front or the rear suspension.Second, the impedance matrix method was used to determine critical structure-borne transfer paths yielding clear results indicating two critical mounts at the rear suspension which dominate the transfer of vibro-acoustic energy. Subsequent physical modification of the critical mount was tested to verify the results of the transmission study.Moreover, deflection shape analysis of the tyre, rim, front and rear suspension was performed to identify possible amplification effects of the TCR phenomenon.