Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 388 results
  • Optimal acoustic error sensing for global active control in a harmonically excited enclosure

     Romeu Garbi, Jordi; Balastegui Manso, Andreu; Pamies Gomez, Teresa; Arcos Villamarin, Robert
    Acoustical physics
    Date of publication: 2014-01-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The performance of an active control system in global control of enclosed sound fields depends largely on the localization of the error sensors, among other factors. In this paper a modified cost function is proposed in order to guarantee the maximum attenuation that can be produced by a set of secondary sources in the case of an harmonically excited sound field. The cost function is modified in order to drive the error signal to the value corresponding to the optimally attenuated sound field, instead of minimizing the squared pressure. To evaluate the performance of the proposed control system, its robustness against unstructured error is also investigated using a set of intensive calculations. Following this approach, the sensors can be located anywhere and the optimal attenuation is reached using an equal number of error sensors and secondary sources. The results also suggest that the greater the number of error sensors than secondary sources the more robust the control system is. This behavior holds for both the usual strategy of minimizing the squared pressure and the approach presented in this paper. However, the latter strategy is more robust than the traditional approach of minimizing the squared pressures and its robustness does not depend on the location of the error sensors. Thus, as a main conclusion, the use of the new cost function leads to a guaranteed efficiency and a more robust control system and gives absolute freedom in selecting the location of the error sensors.

  • A power flow analysis of a double-deck circular tunnel embedded in a full-space

     Clot Razquin, Arnau; Romeu Garbi, Jordi; Arcos Villamarin, Robert; Martin Román, Sara-regina
    Soil dynamics and earthquake engineering (1984)
    Date of publication: 2014-02
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The purpose of the present investigation is to obtain the mean power flow radiated by a double-deck circular tunnel and compares it to the one radiated by a simple circular tunnel. To achieve this, a harmonic line load is applied on the interior floor of the first one and at the bottom of the second one. For the double-deck tunnel, a new analytical model based on the receptance method is developed. The proposed model describes the dynamics of the interior floor using the thin plate theory and considers the Pipe in Pipe (PiP) model to describe the tunnel and soil coupled system. Plain strain conditions are assumed for both systems and conservative coupling is considered between them. Numerical results show significant differences between the power flow radiated by both tunnels, with the one radiated by the double-deck tunnel reaching much higher values. The effect of modifying the flexural rigidity of the interior floor is also presented. © 2013 Elsevier Ltd.

    The purpose of the present investigation is to obtain the mean power flow radiated by a double-deck circular tunnel and compares it to the one radiated by a simple circular tunnel. To achieve this, a harmonic line load is applied on the interior floor of the first one and at the bottom of the second one. For the double-deck tunnel, a new analytical model based on the receptance method is developed. The proposed model describes the dynamics of the interior floor using the thin plate theory and considers the Pipe in Pipe (PiP) model to describe the tunnel and soil coupled system. Plain strain conditions are assumed for both systems and conservative coupling is considered between them. Numerical results show significant differences between the power flow radiated by both tunnels, with the one radiated by the double-deck tunnel reaching much higher values.

  • Detección del daño inducido en aceros para herramientas en el ensayo de indentación esférica mediante la técnica de emisión acústica

     Martinez González, Eva; Ramírez Sandoval, Giselle; Romeu Garbi, Jordi; Casellas, Daniel
    Revista de la Asociación Española de Ensayos No Destructivos
    Date of publication: 2014-01-01
    Journal article

     Share Reference managers Reference managers Open in new window

  • Detection of Failure Mechanisms of Tool Steels by means of Acoustic Emission Technique  Open access

     Martinez González, Eva
    Defense's date: 2014-01-30
    Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Aquesta tesi es centra en calibrar la tècnica d'emissió acústica (EA) per detectar i identificar mecanismes de dany en acersper eines. El procediment de mesura de l¿EA s'ha desenvolupat i calibrat per a dos assajos mecànics: assaig de flexió iassaig d¿indentació esfèrica.A l¿assaig de flexió es generen esquerdes a la superfície de la proveta degudes a la tensió de tracció màxima. El danys'inicia amb la nucleació d'esquerdes (trencament de carburs i deformació plàstica local) i després, les esquerdes espropaguen a través de la matriu metàl¿lica seguint els carburs trencats. La monitorització de l¿assaig amb EA, permetdetectar i identificar cada etapa de la fractura: el trencament de carburs i plastificació (nucleació), creixement de l¿esquerda através de la matriu d¿acer i la fallada catastròfica final de la mostra.L¿assaig d' indentació esfèrica permeten la creació d'una distribució de tensions en la part afectada de la mostra méscomplexa. Amb l¿ aplicació de càrregues baixes, es genera un camp de tensions en el rang elàstic sota l¿indentador esfèric.Durant els assajos, es va detectar activitat d'EA en aquest rang elàstic, i aquests senyals es relacionen amb la ruptura decarburs situats a la zona d'esforç tallant màxim. Una característica important d'aquest assaig és que la ruptura de carburs esporta a terme sense deformació plàstica, i per tant els senyals de dany es van identificar clarament amb el trencament decarburs.En ambdós assajos, el trencament dels carburs va ser confirmat per mitjà de la EA com causa de la nucleació d'esquerdesen acers per a eines. L¿EA va fer possible identificar el trencament de carburs i la propagació d'esquerdes a través de lamatriu metàl¿lica i predir la fractura final de la mostra en els assajos de flexió. Aquesta tesi proposa una nova configuracióde filtratge en assajos de fractura per eliminar senyals espúries a causa del dany provocat pel contacte entre la mostra i elssuports de la màquina, així com una metodologia per a l¿identificació de mecanismes de dany en mostres de mida petitasobre la base de certes característiques de la forma d'ona dels senyals d¿EA. Des del punt de vista de la recerca dematerials, l'acoblament d¿EA amb la configuració que es proposa en cada assaig millora significativament els resultatsobtinguts dels assajos, ja que permet identificar l'evolució del dany durant el cicle de càrrega. Els resultats experimentalsobtinguts avalen el possible ús de l¿EA en el manteniment preventiu d¿eines de conformat a la indústria

    This thesis is focused on the calibration of the Acoustic Emission (AE) technique to detect and identify damage mechanisms in tool steels. The AE measurement procedure has been calibrated for two mechanical tests: fracture test (three-point bending test) and indentation test (spherical indentation). Fracture tests cause cracks due to tensile stress. The damage begins with the nucleation of cracks (cracking carbides and local plastic deformation) and afterwards, the cracks spread through the metallic matrix following the broken carbides. This research proposes an AE filtering process to detect each stage of fracture: the cracking of carbides (nucleation), the stage where the crack passes through to the steel matrix and final catastrophic failure. Spherical indentation tests enable the creation of a more complex distribution of stresses in an affected part of the specimen. Applying low level loads, an elastic field was created in the specimen under the ball indenter. Nevertheless, AE activity was detected in this elastic field, and these signals were related to the breaking of carbides located in the zone of maximum shear stress. An important feature of this test is that the cracking of carbides takes place without plastic deformation, and therefore the damage signals were clearly identified with carbide breakage. In both tests, carbide breakage was confirmed by means of AE as the cause of nucleation of cracks in tool steels. AE made it possible to identify the carbide breakage and the propagation of cracks through the metallic matrix and predict the final fracture of the specimen in bending tests. This thesis proposes a new acquisition and filtering configuration in fracture tests to eliminate spurious signals due to contact damage between the specimen and machine supports, as a methodology for identifying different damage mechanisms in small-sized specimens based on certain AE waveform features. From the standpoint of research into materials, coupling the proposed AE setup in each test significantly improves the tests, since it permits the evolution of the damge to be identified during the loading cycle. The laboratory results obtained endorse the possible use of AE in preventive maintenance in the tool-shaping industry. Barcelona 22

    Aquesta tesi es centra en calibrar la tècnica d'emissió acústica (EA) per detectar i identificar mecanismes de dany en acers per eines. El procediment de mesura de l’EA s'ha desenvolupat i calibrat per a dos assajos mecànics: assaig de flexió i assaig d’indentació esfèrica. A l’assaig de flexió es generen esquerdes a la superfície de la proveta on la tensió de tracció és màxima. El dany s'inicia amb la nucleació d'esquerdes (trencament de carburs i deformació plàstica local) i després, les esquerdes es propaguen a través de la matriu metàl•lica seguint els carburs trencats. La monitorització de l’assaig amb EA, permet detectar i identificar cada etapa de la fractura: el trencament de carburs i plastificació (nucleació), creixement de l’esquerda a través de la matriu d’acer i la fallada catastròfica final de la mostra. L’assaig d' indentació esfèrica permeten la creació d'una distribució de tensions en la part afectada de la mostra més complexa. Amb l’ aplicació de càrregues baixes, es genera un camp de tensions en el rang elàstic sota l’indentador esfèric. Durant els assajos, es va detectar activitat d'EA en aquest rang elàstic, i aquests senyals es relacionen amb la ruptura de carburs situats a la zona d'esforç tallant màxim. Una característica important d'aquest assaig és que la ruptura de carburs es porta a terme sense deformació plàstica, i per tant els senyals de dany es van identificar clarament amb el trencament de carburs. En ambdós assajos, el trencament dels carburs va ser confirmat per mitjà de la EA com causa de la nucleació d'esquerdes en acers per a eines. L’EA va fer possible identificar el trencament de carburs i la propagació d'esquerdes a través de la matriu metàl•lica i predir la fractura final de la mostra en els assajos de flexió. Aquesta tesi proposa una nova configuració de filtratge en assajos de fractura per eliminar senyals espúries a causa del dany provocat pel contacte entre la mostra i els suports de la màquina, així com una metodologia per a l’identificació de mecanismes de dany en mostres de mida petita sobre la base de certes característiques de la forma d'ona dels senyals d’EA. Des del punt de vista de la recerca de materials, l'acoblament d’EA amb la configuració que es proposa en cada assaig millora significativament els resultats obtinguts dels assajos, ja que permet identificar l'evolució del dany durant el cicle de càrrega. Els resultats experimentals obtinguts avalen el possible ús de l’EA en el manteniment preventiu d’eines de conformat a la industria.

    Esta tesis se centra en calibrar la técnica de la emisión acústica (EA) para detectar e identificar los mecanismos de daño en aceros para herramientas. El procedimiento de medida de la EA se ha desarrollado y calibrado para dos ensayos mecánicos: ensayo de flexión y de indentación esférica. En el ensayo de flexión se generan grietas en la superficie de la probeta donde la tensión de tracción es máxima. El daño se origina con la nucleación de las grietas (rotura de carburos y deformación plástica local) y después, las grietas propagan a través de la matriz metálica siguiendo la línea de carburos rotos. La monitorización del ensayo con EA permite detectar e identificar cada una de las etapas de la fractura: rotura de carburos y plastificación (nucleación), crecimiento de grietas por la matriz de acero y el fallo catastrófico final de la muestra. El ensayo de indentación esférica permite la creación de una distribución de tensiones en la parte afectada de la muestra más compleja. Con la aplicación de cargas bajas, se genera un campo de tensiones en el rango elástico situado bajo el indentador esférico. En los ensayos, se detectó actividad de EA en este rango, y estas señales se pudieron relacionar con la rotura de carburos situados en la zona de tensión tangencial màxima. Una característica importante de este ensayo es que la rotura de los carburos tiene lugar sin deformación plàstica del material, y por tanto las señales de daño se identificarion claramente con la rotura de estos carburos. En ambos ensayos, la rotura de los carburos fue confirmada mediante EA como causa de la nucleación de grietas en aceros para herramientas. La EA hizo posible identificar la rotura de carburos primarios y la propagación de grietas a través de la matriz metálica, y predecir la fractura final de la muestra en los ensayos de flexión. En esta tesis se propone una nueva configurción de filtrado para ensyaos de flexión para eliminar las señales espúrias a causa del daño rpovocado por el contacto entre la probeta y los soportes de la máquina, así como una metodoología para identificar los mecanismos de daño en muestras de pequeñas deimensiones sobre la base de ciertas características de la forma de onda de las señales de la forma de onda de las señales de EA. Desde el punto de vista de investigación de materiales, incorporar la EA, con la configuración propuesta, a cada uno de los ensayos mejora significativamente los resultados obtenidos, ya que permite identificar la evolución del daño durante el ciclo de carga. Los resultados experimentales obtenidos avalan el posible uso de la EA para el mantenimiento preventivo de herramientas de conformado en la industria.

  • Active control of aircraft fly-over sound transmission through an open window

     Pamies Gomez, Teresa; Romeu Garbi, Jordi; Genesca Francitorra, Meritxell; Arcos Villamarin, Robert
    Applied acoustics
    Date of publication: 2014-10-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents an experimental work on active control of sound transmission through a restricted opening bottom hinged window. The main goal of the work is to demonstrate the feasibility of the active technique to limit the loss of attenuation due to the aperture of windows, and its application to aircraft fly-over incident noise. The experimental window is placed in an exposed facade of a dwelling close to an airport and subject to fly-by aircraft noise. The active control is configured to cancel the pressure at the aperture using a single-input single-output feedforward adaptive system. As a result, a reduction of sound transmission is achieved with low power consumption. In global terms, an increase of almost 3 dB of transmission loss (with respect to the partially opened window insulation values) in the low frequency range (below 160 Hz and according to the National Danish Method for evaluating low frequency noise) is demonstrated, which is equivalent to a reduction of 50% in the loss of insulation caused by opening the window. (C) 2014 Elsevier Ltd. All rights reserved.

    This paper presents an experimental work on active control of sound transmission through a restricted opening bottom hinged window. The main goal of the work is to demonstrate the feasibility of the active technique to limit the loss of attenuation due to the aperture of windows, and its application to aircraft fly-over incident noise. The experimental window is placed in an exposed façade of a dwelling close to an airport and subject to fly-by aircraft noise. The active control is configured to cancel the pressure at the aperture using a single-input single-output feedforward adaptive system. As a result, a reduction of sound transmission is achieved with low power consumption. In global terms, an increase of almost 3 dB of transmission loss (with respect to the partially opened window insulation values) in the low frequency range (below 160 Hz and according to the National Danish Method for evaluating low frequency noise) is demonstrated, which is equivalent to a reduction of 50% in the loss of insulation caused by opening the window. © 2014 Elsevier Ltd. All rights reserved.

  • A dynamical model of a double-deck circular tunnel embedded in a full-space

     Clot Razquin, Arnau
    Defense's date: 2014-02-20
    Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract  Share Reference managers Reference managers Open in new window

    Aquesta tesis presenta un model dinàmic tridimensional d¿un túnel circular de dos pisos situat en el si d¿un espai infinit. El model fa ús del mètode de la receptància per a obtenir la resposta de l¿estructura completa a partir de la resposta de les seves parts. Els subsistemes considerats són, per una banda, el terra interior, i per l¿altra, el sistema acoblat túnel-terreny. El comportament dinàmic del primer es modelitza mitjançant la teoria clàssica de placa prima i el model Pipe-in-Pipe és l¿escollit per a descriure el segon. Com que el model proposat assumeix que el sistema és geomètricament invariant en la direcció de circulació dels trens, l¿acoblament dels subsistemes es pot realitzar en el domini nombre d¿ona-freqüència. Un cop el model ha estat formulat, es detallen els principals aspectes a tenir en compte en la seva computació numèrica i s¿interpreten els resultats obtinguts. La resposta d¿un túnel de dos pisos tant a una excitació dinàmica com a una de quasiestàtica es comparada a la resposta obtinguda en el cas d¿un túnel d'un únic pis. La primera comparativa es realitza mitjançant un estudi del flux de potència radiat per ambdues estructures sota l¿aplicació d¿una càrrega harmònica lineal. Les principals diferències entre les magnituds i els patrons de radiació són detallades i discutides. La segona comparativa es realitza calculant el flux total d¿energia que travessa una certa superfície del terreny quan una càrrega que es desplaça a velocitat constant es aplicada sobre ambdós túnels. La comparativa entre les respostes dels tunels es realitza per un ampli rang de velocitats. Finalment, es presenta un model complert de via-túnel-terreny obtingut a partir de l¿acoblament d¿un model de superestructura al model de túnel prèviament desenvolupat.

  • Application of a fast pre-calculated model for vibration impact assessment from underground trains to Metro Line 9 of Barcelona

     Balastegui Manso, Andreu; Arcos Villamarin, Robert; Romeu Garbi, Jordi; Pamies Gomez, Teresa
    Noise control engineering journal
    Date of publication: 2013-03
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The prediction of vibration levels near underground trains is of growing importance for newly constructed infrastructures in cities. Before construction, preliminary studies of vibration impact need to be undertaken in order to identify the buildings that may be affected based on vibration contamination laws and modify the railway line or the type of superstructure if necessary. These studies need fast and economic models due to the large areas they need to cover. The present study aims at predicting the vibration impact for the new Line 9 of Barcelona Underground which is 48 km long. The solution presented is a fast pre-calculated 2D FEM model which is run once for a set of different soil types and tunnel depths, obtaining sets of surface vibration levels. Interpolating between the depths and distances of the tabulated results can be used as a very fast model for prediction. The model is calibrated with measurements in the same conditions (rolling stock and superstructure) as those expected in Line 9 and offers an accuracy not far from current 2.5D and 3D models.

  • Filtering of acoustic emission signals for the accurate identification of fracture mechanisms in bending tests

     Martinez González, Eva; Picas Anfruns, Ingrid; Romeu Garbi, Jordi; Casellas, Daniel
    Materials transactions
    Date of publication: 2013
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this manuscript, acoustic emission (AE) analysis is used to identify the fracture mechanisms that take place during a three-point bending test of steel specimens. However, an important source of AE was detected and related to the deformation of the supports and the surface of the steel specimen in contact. This source creates AE signals that are very high in number and amplitude, and prevent determining accurately the onset stress for fracture mechanisms in specimens. A signal filtering is proposed based on the properties of the initial part of the recorded AE waveform, combined with a linear localization. The filtering successfully allows the AE signals to be classified according to their source as background noise, damage due to contact of the specimen surface to the supports and fracture mechanisms occurring in the specimen microstructure as a result of the bending test. The aforementioned filter has been successfully applied in case of a cold work tool steel DIN 1.2379 to determine accurately the stress level at which the first damaging mechanisms start to occur in the microstructure in situ during the three-point bending test. Filtered AE signal results indicating damage in the microstructure have been corroborated by inspection of the specimen's surface in a Confocal Microscope. In default of using the proposed filter, unfiltered signals have been estimated to lead to an overestimation of critical stresses of about 20%, what is undesirable for most applications. © 2013 The Japan Institute of Metals and Materials.

  • Access to the full text
    New siren tones optimised for increased detectability distances of emergency vehicles  Open access

     Balastegui Manso, Andreu; Romeu Garbi, Jordi; Clot Razquin, Arnau; Martin Román, Sara-regina
    Applied acoustics
    Date of publication: 2013-06
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Sirens from emergency vehicles are particularly annoying for people living in the vicinities of emergency centres. In order to reduce their discomfort, the present work computes the optimal output power and frequency content of the sirens by taking into account the car noise reduction, the background noise inside the car and the hearing threshold. The combination of these parameters gives rise to frequency windows where the sirens are more effective, hence new siren tones are proposed and their annoyance is assessed through a jury test procedure. The new tones can either increase the detectability distance by 40% without increasing their annoyance or reduce their sound pressure level by 3 dB while keeping their effectiveness in being detected. (C) 2013 Elsevier Ltd. All rights reserved.

    Sirens from emergency vehicles are particularly annoying for people living in the vicinities of emergency centres. In order to reduce their discomfort, the present work computes the optimal output power and frequency content of the sirens by taking into account the car noise reduction, the background noise inside the car and the hearing threshold. The combination of these parameters gives rise to frequency windows where the sirens are more effective, hence new siren tones are proposed and their annoyance is assessed through a jury test procedure. The new tones can either increase the detectability distance by 40% without increasing their annoyance or reduce their sound pressure level by 3 dB while keeping their effectiveness in being detected.

    Postprint (author’s final draft)

  • Measurement of aircraft noise in a high background noise environment using a microphone array

     Genesca Francitorra, Meritxell; Romeu Garbi, Jordi; Arcos Villamarin, Robert; Martin Román, Sara-regina
    Transportation research. Part D, transport and environment
    Date of publication: 2013-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Aircraft tracking by means of the Acoustical Doppler Effect

     Martin Román, Sara-regina; Genesca Francitorra, Meritxell; Romeu Garbi, Jordi; Pamies Gomez, Teresa
    Aerospace science and technology
    Date of publication: 2013-07
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The present paper presents a passive acoustic method for aircraft tracking. The Acoustical Doppler Effect, characteristic of signals received by a mesh of spatially distributed microphones is the basis of the method. A one-dimensional version of the Ambiguity function permits the calculation of the frequency stretch factor that exists between the sound signals received by a pair of microphones. The expression for this frequency stretch is a function of the aircraft position and velocity which are estimated by a Genetic Algorithm. The method is suitable for all kinds of aircraft and requires only seven microphones plus the prior knowledge of only the aircraft position and velocity at a given time. Results are given for a simulation test of a 3D straight trajectory of the aircraft and for a sound-propagation model which considers geometrical spreading and atmospheric absorption of sound for a homogeneous medium. The influence of the atmospheric absorption is evaluated and the independence of the method with respect to microphone distribution is proven. The performance of the tracking method has also been evaluated in front of possible inaccuracy on the microphones synchronization.

    The present paper presents a passive acoustic method for aircraft tracking. The Acoustical Doppler Effect, characteristic of signals received by a mesh of spatially distributed microphones is the basis of the method. A one-dimensional version of the Ambiguity function permits the calculation of the frequency stretch factor that exists between the sound signals received by a pair of microphones. The expression for this frequency stretch is a function of the aircraft position and velocity which are estimated by a Genetic Algorithm. The method is suitable for all kinds of aircraft and requires only seven microphones plus the prior knowledge of only the aircraft position and velocity at a given time. Results are given for a simulation test of a 3D straight trajectory of the aircraft and for a sound-propagation model which considers geometrical spreading and atmospheric absorption of sound for a homogeneous medium. The influence of the atmospheric absorption is evaluated and the independence of the method with respect to microphone distribution is proven. The performance of the tracking method has also been evaluated in front of possible inaccuracy on the microphones synchronization.

  • Passive acoustic method for aircraft localization  Open access

     Martin Román, Sara-regina
    Defense's date: 2013-07-15
    Department of Mechanical Engineering, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    La tesi desenvolupa, implementa i valida un mètode acústic per a la localització d¿aeronaus. El mètode es basa en l¿efecte Doppler que es percep en els registres de diferents micròfons distribuïts al voltant d¿un aeroport. La versió u-dimensional de la funció d¿ambigüitat permet el còmput del factor de compressió o expansió que sorgeix entre els registres freqüencials d¿ un parell de micròfons. Aquest factor freqüencial es pot expressar matemàticament en funció de la posició i velocitat de l¿aeronau, que s¿estimen en aquesta tesi a partir d¿algoritmes genètics. El mètode només requereix de set micròfons i el coneixement previ de la posició de l¿avió en un moment donat. Els principals avantatges del mètode són que és un mètode vàlid per qualsevol tipus d¿aeronau, no només per avions d¿hèlix o helicòpters, i que no restringeix a vols de baixa alçada. La seva aplicació podria ser, per exemple, complementar un sistema de monitorització de soroll aeri o bé supervisar l¿activitat dels aeroports petits que no disposen de sistemes de radar. Aquesta investigació inclou el desenvolupament teòric del mètode així com la descripció detallada de la seva implementació. Per tal d¿avaluar l¿efectivitat del mètode, es presenten i analitzen resultats obtinguts a partir de diverses simulacions. Com a primer cas, es considera que el so es propaga en un medi conservatiu, és a dir, el so que es propaga des de la font fins als receptors només es veu afectat per l¿atenuació geomètrica. Sota aquest model senzill de propagació, s¿ha analitzat l¿accuracy de cada un dels passos del mètode i els resultats obtinguts posen de manifest una bona ... del mètode. Tenint en compte que les distàncies entre els micròfons i l¿avió en vol són llargues, l¿atenuació atmosfèrica influeix també en la propagació del so emès per l¿avió. Per tant, el segon cas de simulacions que s¿han dut a terme considera un medi de propagació homogeni i no conservatiu amb l¿objectiu d¿avaluar la influència de l¿atenuació atmosfèrica en la localització acústica de l¿aeronau. Sota aquestes condicions, també s¿ha analitzat l¿eficàcia del mètode en funció de la distribució de micròfons. A més, el mètode de localització s¿ha posat a prova sota possibles errors en la sincronització dels set micròfons. Finalment, s¿ha dut a terme una validació experimental del mètode amb una avioneta de radio control al Club Aeronàutic Egara. La descripció d¿aquest test experimental es detalla en la tesis així com els resultats obtinguts que demostren la validesa satisfactòria del mètode.

    The present thesis investigates a passive acoustic method to locate maneuvering aircraft. The method is based on the acoustical Doppler effect, as a particular effect of the signals received by a mesh of spatially distributed microphones. A one-dimensional version of the ambiguity function allows for the calculation of the frequency stretch factor that occurs between the sound signals received by a pair of microphones. The mathematical expression for this frequency stretch is a function of the aircraft position and velocity, both of them being estimated by a genetic algorithm. The method requires only a minimum of seven microphones and the prior knowledge of the aircraft position and velocity at a given time. The advantages of the method are that it is suitable for all kind of aircraft, not only propeller-driven, and is not restricted to low heights above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports activities. This doctoral research includes the theoretical background of the method as well as the detailed description of its implementation. To assess the performance of the method, results from computer simulations are discussed. First of all, noise propagation is considered in a lossless medium, thus only geometrical spreading influences the sound emitted by the source traveling to the receivers. The accuracy of each step of the method has been evaluated and the results obtained reveal acceptable performance. Due to the large distances between microphones and the aircraft in flight, the atmospheric attenuation plays a major roll. Therefore, computer simulations have also been carried out under the assumption of an homogeneous but non lossless medium to evaluate the influence of the atmospheric absorption on the aircraft location. Under these conditions, the performance of the method with respect to the microphone distribution is discussed. Moreover, the location method has also been tested for a possible inaccuracy on the microphones synchronization. Finally, an outdoor experimental validation of the acoustic method has been carried out with a radio control airplane. The description of the experimental test is detailed in the present work as well as the results obtained.

    La tesi desenvolupa, implementa i valida un mètode acústic per a la localització d’aeronaus. El mètode es basa en l’efecte Doppler que es percep en els registres de diferents micròfons distribuïts al voltant d’un aeroport. La versió u-dimensional de la funció d’ambigüitat permet el còmput del factor de compressió o expansió que sorgeix entre els registres freqüencials d’ un parell de micròfons. Aquest factor Freqüencial es pot expressar matemàticament en funció de la posició i velocitat de l’aeronau, que s’estimen en aquesta tesi a partir d’algoritmes genètics. El mètode només requereix de set micròfons i el coneixement previ de la posició de l’avió en un moment donat. Els principals avantatges del mètode són que és un mètode vàlid per qualsevol tipus d’aeronau, no només per avions d’hèlix o helicòpters, i que no restringeix a vols de baixa alçada. La seva aplicació podria ser, per exemple, complementar un sistema de monitorització de soroll aeri o bé supervisar l’activitat dels aeroports petits que no disposen de sistemes de radar. Aquesta investigació inclou el desenvolupament teòric del mètode així com la descripció detallada de la seva implementació. Per tal d’avaluar l’efectivitat del mètode, es presenten i analitzen resultats obtinguts a partir de diverses simulacions. Com a primer cas, es considera que el so es propaga en un medi conservatiu, és a dir, el so que es propaga des de la font fins als receptors només es veu afectat per l’atenuació geomètrica. Sota aquest model senzill de propagació, s’ha analitzat l’accuracy de cada un dels passos del mètode i els resultats obtinguts posen de manifest una bona ... del mètode. Tenint en compte que les distàncies entre els micròfons i l’avió en vol són llargues, l’atenuació atmosfèrica influeix també en la propagació del so emès per l’avió. Per tant, el segon cas de simulacions que s’han dut a terme considera un medi de propagació homogeni i no conservatiu amb l’objectiu d’avaluar la influència de l’atenuació atmosfèrica en la localització acústica de l’aeronau. Sota aquestes condicions, també s’ha analitzat l’eficàcia del mètode en funció de la distribució de micròfons. A més, el mètode de localització s’ha posat a prova sota possibles errors en la sincronització dels set micròfons. Finalment, s’ha dut a terme una validació experimental del mètode amb una avioneta de radio control al Club Aeronàutic Egara. La descripció d’aquest test experimental es detalla en la tesis així com els resultats obtinguts que demostren la validesa satisfactòria del mètode.

  • Actualització del mapa estratègic de soroll i proposta de mapa de capacitat acústica del municipi de Terrassa

     Llorens Baucells, Maria; Alsina Sánchez, Antoni; Latorre Raez, Josep; Romero Blasco, Jesús; López López, Susi; Jimenez Diaz, Santiago; Pamies Gomez, Teresa; Romeu Garbi, Jordi
    Date: 2012-10
    Report

     Share Reference managers Reference managers Open in new window

  • On the use of a linear microphone array to measure wind turbine aerodynamic noise

     Genesca Francitorra, Meritxell; Romeu Garbi, Jordi; Pamies Gomez, Teresa; Solé, Jaume
    Wind energy
    Date of publication: 2012-01-11
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    A linear microphone array is shown to be a simple tool to locate aerodynamic sound sources on a horizontal axis wind turbine. This paper discusses the capabilities and limitations of a linear microphone array to locate sound sources and measure aerodynamic noise on the blades of a horizontal axis wind turbine rotor. Compared with a planar microphone array, a linear array requires fewer microphones to achieve the same resolution, a simpler structure to support it and a simpler signal processing algorithm. For a linear array, areas exist in the rotor plane where the sources cannot be located unambiguously. For certain applications, it is not necessary to map the whole rotor plane. This paper also shows the result of an experimental test aimed at locating and measuring aerodynamic sound sources on the three blades of a wind turbine. Each blade received a different surface treatment, with the goal of comparing their relative sound emission levels. The test was carried out with a 10.32 m linear microphone array, placed horizontally near the ground, extending parallel to the rotor plane. The results show that for all three blades, most of the noise is generated in the outer 25% of the blade span, with a maximum occurring just after the blade has passed the horizontal position going downwards. Results also show that tripped blade is the noisiest of the three, whereas the smoothest, polished blade is clearly the quietest. Copyright © 2012 John Wiley & Sons, Ltd.

  • Some analytical aspects of viscoelastic Lamb¿s problem for improving its numerical evaluation

     Arcos Villamarin, Robert; Romeu Garbi, Jordi; Clot Razquin, Arnau; Genesca Francitorra, Meritxell
    Wave motion
    Date of publication: 2012-08-27
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Two analytical modifications of the original viscoelastic time-harmonic Lamb’s problem expressions are presented with the aim of improving their numerical integration efficiency. Firstly, a new change of variable in the Lamb’s problem integrands is proposed, which allows a standardization of the integration sampling vector and a complete spatialfrequency field solution after performing only one numerical integration/transformation. Secondly, the Lamb’s problem static integrands are modified and introduced into the original integrands to reduce their spectral content at high wavenumbers and, therefore, the sampling vector lengths needed to avoid aliasing.

  • Micro-mechanical damage in tool steels analyzed by acoustic emission technique

     Picas, Ingrid; Martinez González, Eva; Casellas, Daniel; Romeu Garbi, Jordi
    Journal of acoustic emission
    Date of publication: 2012-12-30
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The carbides in tool steels act as hard particles and dictate the wear resistance. The origin of failure of these steels is mostly related with the carbide cracking, as a nucleation site of final cracks. This paper shows the acoustic emission (AE) signals related with the nucleation (carbide cracking) and the crack growth (in the metallic matrix) during a monotonic bending test of a tool steel obtained by ingot metallurgy routes (DIN 1.2379). The paper presents a relationship between the frequency spectrum of AE signals obtained and the microscopic images during the test.

  • Analysis of fracture resistance of tool steels by means of acoustic emission

     Martinez González, Eva; Picas Anfruns, Ingrid; Casellas Padro, Daniel; Romeu Garbi, Jordi
    The e-journal and exhibition of non-destructive testing
    Date of publication: 2012-02-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Aircraft noise-monitoring according to ISO 20906: evaluation of uncertainty derived from the human factors affecting event detection

     Asensio, Alberto; Ausejo, Miguel; Kambrosic, Kristian; Kang, Jiang; Moschioni, Giovanni; Pagán, R.; Pavón, I.; Romeu Garbi, Jordi; Trujillo, J. A.; Vigano, Giacomo; Ruiz Delgado, Manuel; Recuero López, Manuel
    Applied acoustics
    Date of publication: 2012
    Journal article

     Share Reference managers Reference managers Open in new window

  • Estudio micro-mecánico de daño en aceros para herramientas mediante la técnica de la emisión acústica

     Martinez González, Eva; Picas, Ingrid; Casellas, Daniel; Romeu Garbi, Jordi
    Revista de la Asociación Española de Ensayos No Destructivos
    Date of publication: 2012-09-01
    Journal article

     Share Reference managers Reference managers Open in new window

  • Actualització del mapa estratègic de soroll del municipi de Barberà del vallès

     González Balsera, Manuel; Suso, Jesús; Jimenez Diaz, Santiago; Pamies Gomez, Teresa; Romeu Garbi, Jordi
    Date: 2012-11
    Report

     Share Reference managers Reference managers Open in new window

  • CONTROL ACTIVO DE TRANSMISION DE RUIDO A TRAVES DE APERTURAS

     Pamies Gomez, Teresa; Balastegui Manso, Andreu; Arcos Villamarin, Robert; Romeu Garbi, Jordi
    Participation in a competitive project

     Share

  • Impacto acústico generado como consecuencia de la implantación de un skate park

     Jimenez Diaz, Santiago; Romeu Garbi, Jordi; Alsina Sánchez, Antoni
    Congreso Ibero-americano de Acústica
    Presentation's date: 2012-10-02
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Un skate park es una instalación singular formada por un conjunto de elementos y obstáculos, fuentes sonoras potenciales, que se imlpanta en un entorno urbano abierto. El estudio de impacto acústico de este tipo de actividad no se puede realizar por evaluación de una actividad respecto de los receptores será diferente en cada caso. El cálculo por simulación permite incluir todas estas variables, pero requiere tener previamente la potencia acústica radiada y la directividad de cada fuente sonora (actividad del patinador sobre el elemento y obstáculo) de que consta la instalación del skate park. Una vez caracterizadas las fuentes de ruido, usando los datos topográficos y meteorólogicos del lugar, se determinan mediante simulación informática, los niveles de inmisión sonora procedentes de las diferentes fuentes del skate park que llegan a la fachada de los receptores.

  • Street categorization for the estimation of day levels using short-term measurements

     Romeu Garbi, Jordi; Genesca Francitorra, Meritxell; Pamies Gomez, Teresa; Jimenez Diaz, Santiago
    Applied acoustics
    Date of publication: 2011-07
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Sound radiation from an aperture in a rectangular enclosure under low modal conditions

     Pamies Gomez, Teresa; Romeu Garbi, Jordi; Genesca Francitorra, Meritxell; Balastegui Manso, Andreu
    Journal of the Acoustical Society of America
    Date of publication: 2011-07
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Passive acoustic method for tracking moving sound sources

     Genesca Francitorra, Meritxell; Romeu Garbi, Jordi; Pamies Gomez, Teresa; Balastegui Manso, Andreu
    Acta acustica united with acustica
    Date of publication: 2011-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Determination of the near field distance for point and line sources acting on the surface of an homogeneous and viscoelastic half-space

     Arcos Villamarin, Robert; Romeu Garbi, Jordi; Balastegui Manso, Andreu; Pamies Gomez, Teresa
    Soil dynamics and earthquake engineering (1984)
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Mapa estratègic de soroll de la ctra. BV-5001 entre els P.Q. 0 i 19+885

     Jimenez Diaz, Santiago; Romeu Garbi, Jordi
    Date: 2011-04
    Report

     Share Reference managers Reference managers Open in new window

  • TECCOL11-1-0007-15

     Romeu Garbi, Jordi
    Participation in a competitive project

     Share

  • Access to the full text
    Contaminació acústica  Open access

     Romeu Garbi, Jordi; Jimenez Diaz, Santiago
    Date of publication: 2011
    Book chapter

    Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

  • A model for railway induced ground vibrations in the frame of preliminary assessment studies  Open access

     Arcos Villamarin, Robert
    Defense's date: 2011-07-13
    Department of Mechanical Engineering, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    This thesis focuses on the development of an analytical model for the generation and propagation parts of a global model of ground induced vibrations to be used in preliminary assessment studies for the case of at-grade railway infrastructures. The model is designed prioritising its speed, simplicity and usability ahead its accuracy modelling the real railway system. This model takes into account the subgrade as a viscoelastic and homogeneous half-space, the superstructure as a 2-layer supporting model and the vehicle as 1DOF system. With the aim of simplify the model, the superstructure/subgrade interaction is studied in terms of the wheel/rail contact dynamics, bounding in what cases this interaction can be neglected. The adaptation of this model when a far eld semi-analytical model is desired to be used as the propagation model is fully developed, by means of the dimensioning of the near eld and far eld regions.

  • Active control of sound transmission through an aperture

     Pamies Gomez, Teresa
    Defense's date: 2011-07-18
    Department of Mechanical Engineering, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • On the power and frequency of auditory signals on emergency vehicles

     Balastegui Manso, Andreu; Romeu Garbi, Jordi; Clot, Arnau; Martin Román, Sara-regina
    International Congress and Exposition on Noise Control Engineering
    Presentation's date: 2011-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Two step optimization of transducer locations in single input single output tonal global active noise control in enclosures

     Palacios Higueras, Jose Ignacio; Romeu Garbi, Jordi; Balastegui Manso, Andreu
    Journal of vibration and acoustics. Transactions of the ASME
    Date of publication: 2010-12
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Global active control of sound can be achieved inside enclosures under low modal acoustic fields. However, the performance of the system depends largely on the localization of the elements of the control system. For a purely acoustic active control system in which secondary acoustic sources (loudspeakers) and pressure transducers (microphones) as error sensors are used, several optimization strategies have been proposed. These strategies usually rely on partial approximation to the problem, focusing on the study of number and localization of secondary sources without considering error transducers, or selecting the best positions of secondary sources and error transducers of an initial set of candidate locations for these elements. The strategy presented here for tonal global active noise control of steady states comprises two steps; the first is rather common for this sort of problem and its goal is to find the best locations for secondary sources and their strengths by minimizing the potential energy of the enclosure. The second step is the localization of the error transducer, which ensures the results of the first step. It is analytically demonstrated that for a single input single output system, the optimum location of error transducers is at a null pressure point of the optimally attenuated acoustic field. It is also shown that in a real case, the optimum position is that of a minimum of the optimally attenuated acoustic field. Finally, a numerical validation of this principle is carried out in a parallelipedic enclosure.

  • Analysis of fracture resistance of tool steels by means of acoustic emission

     Martinez González, Eva; Picas Anfruns, Ingrid; Casellas Padro, Daniel; Romeu Garbi, Jordi
    Journal of acoustic emission
    Date of publication: 2010-12-10
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The automotive manufacturers currently use advanced high-strength steels (AHSS) to produce lightweight vehicles with increased safety performance. While showing excellent strengthto-weight ratios, AHSS have several limitations due to the high loads required in cold forming and cutting processes, which lead to accelerated wear and premature fracture of tools. Thus, new tool materials with improved mechanical behavior ought to be developed with regard to the tool failure mechanisms. The aim of this work is to shed light on the fracture mechanisms acting in tools (i.e. crack nucleation and propagation) applying the acoustic emission (AE) technique. Bending tests using two different tool steels were monitored in order to establish a relationship between AE signals and fracture events.

  • Acelerómetros y sensores de vibración

     Romeu Garbi, Jordi; Genesca Francitorra, Meritxell
    Automática e instrumentación
    Date of publication: 2010-04
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Aircraft noise monitoring with linear microphone arrays

     Genesca Francitorra, Meritxell; Romeu Garbi, Jordi; Pamies Gomez, Teresa; Sanchez Venegas, Angel
    IEEE aerospace and electronic systems magazine
    Date of publication: 2010-01
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Estudi de les vibracions provocades per l´explotació de la Línia 9 a l´interior dels túnels i als edificis exteriors. Assaig al túnel de la Línia 9 a St. Cosme, El Prat de Llobregat

     Cardona Foix, Salvador; Martinez Miralles, Jordi Ramon; Romeu Garbi, Jordi; Balastegui Manso, Andreu; Tejedo Sobrino, Jose Luis
    Date: 2010-06
    Report

     Share Reference managers Reference managers Open in new window