The Transfer Function (TF) relates the structure-borne noise level of the hull with the Underwate... more The Transfer Function (TF) relates the structure-borne noise level of the hull with the Underwater Radiated Noise (URN). Therefore, the acoustic noise generated by the vibrations of the hull of a ship could be estimated from real measurements of the structure-borne noise levels of the hull by applying the TF in real time. This function depends on the material of the hull of the ship. In this paper, real measurements of the structure-borne noise level of the hull and URN of two ships constructed of steel and Glass fiber Reinforced Plastics (GRP) are used to estimate the TF of the hull.
In this paper an alternative procedure to vibro-acoustics study of beam-type structures is presen... more In this paper an alternative procedure to vibro-acoustics study of beam-type structures is presented. With this procedure, it is possible to determine the resonant modes, the bending wave propagation velocity through the study of the radiated acoustic field and their temporal evolution in the frequency range selected. As regards the purely experimental aspect, it is worth noting that the exciter device is an actuator similar to is the one employed in distributed modes loudspeakers; the test signal used is a pseudo random sequence, in particular, an MLS (Maximum length Sequence), facilitates post processing. The study case was applied to two beam-type structures made of a sandstone material called Bateig. The experimental results of the modal response and the bending propagation velocity are compared with well-established analytical solution: Euler-Bernoulli and Timoshenko models, and numerical models: Finite Element Method-FEM, showing a good agreement.
Journal of the Acoustical Society of America, May 1, 2008
layers composing it. These types of devices are composed by monolithic glass and an intermediate ... more layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.
ANNALS OF THE ORADEA UNIVERSITY. Fascicle of Management and Technological Engineering., 2010
The object of the present work is to make a contribution to the quantification of the vibration b... more The object of the present work is to make a contribution to the quantification of the vibration behavior of the walls of two loudspeaker prototypes mounted in closed boxes, made of different materials. Using the finite elements method, a coupled fluid-structure numerical model of a loudspeaker-box system was implemented. The numerical model was calibrated from the experimental results obtained on a real model by means of modal analysis, vibration and pressure measurements. The conclusion is that the sonorous response of the system is affected by the vibration behavior of the box and its material.
There are many different types of sound absorbent materials. Nowadays, some simple models are use... more There are many different types of sound absorbent materials. Nowadays, some simple models are used to characterize these materials. These models are based on empirical equations obtained from measured data. The models are only valid for the studied materials. In the references there are different empirical models to predict the behaviour of some materials. In this investigation, a study of the behaviour of these simple models has been carried out, and some empirical equations for several sound absorbent materials have been proposed.
ABSTRACT In the present work, a three-dimensional (3D) formulation based on the method of fundame... more ABSTRACT In the present work, a three-dimensional (3D) formulation based on the method of fundamental solutions (MFS) is applied to the study of acoustic horns. The implemented model follows and extends previous works that only considered two-dimensional and axisymmetric horn configurations. The more realistic case of 3D acoustic horns with symmetry regarding two orthogonal planes is addressed. The use of the domain decomposition technique with two interconnected sub-regions along a continuity boundary is proposed, allowing for the computation of the sound pressure generated by an acoustic horn installed on a rigid screen. In order to reduce the model discretization requirements for these cases, Green’s functions derived with the image source methodology are adopted, automatically accounting for the presence of symmetry conditions. A strategy for the calculation of an optimal position of the virtual sources used by the MFS to define the solution is also used, leading to improved reliability and flexibility of the proposed method. The responses obtained by the developed model are compared to reference solutions, computed by well-established models based on the boundary element method. Additionally, numerically calculated acoustic parameters, such as directivity and beamwidth, are compared with those evaluated experimentally.
... Localización: V Jornades de Xarxes d¿Investigació en Docència Universitària [Recurso electrón... more ... Localización: V Jornades de Xarxes d¿Investigació en Docència Universitària [Recurso electrónico]: V Jornadas de Redes de Investigación en Docencia Universitaria. / Marcos IglesiasMartínez ( aut. ), Francesc Pastor Verdú ( aut. ), 2007, ISBN 978-84-690-77238 , pág. 27; ...
En los sistemas de reproducción sonora es habitual la utilización de altavoces dinámicos. Sin emb... more En los sistemas de reproducción sonora es habitual la utilización de altavoces dinámicos. Sin embargo, en aplicaciones específicas, puede ser necesaria y/o conveniente la utilización de altavoces alternativos con superficies planas como diafragma, como los electrostáticos o los basados en la tecnología NXT c. Estos altavoces generan el campo acústico mediante la vibración de una superficie rectangular. Se puede suponer, en una primera aproximación, que todos los puntos sobre su superficie se mueven con la misma amplitud y fase. En este trabajo se analiza el comportamiento directivo de este tipo de superficies para la generación del campo acústico y se simula su comportamiento, comparándolo con medidas experimentales.
La evaluación del ruido transmitido por flancos en edificación es esencial para el estudio del ai... more La evaluación del ruido transmitido por flancos en edificación es esencial para el estudio del aislamiento a ruido aéreo. Desde el punto de vista numérico, para la determinación de las transmisiones laterales es necesario conocer un parámetro conocido como índice de reducción vibracional. Para obtener este parámetro con el objetivo de conocer el comportamiento acústico de todo el conjunto constructivo, es necesario conocer la diferencia de niveles de velocidad y el tiempo de reverberación estructural. Indeterminaciones bien en la diferencia de niveles de velocidad, bien en el tiempo de reverberación estructural supondrán desviaciones en la determinación del aislamiento global de todo el conjunto constructivo. Existen normativas (UNE EN 12354-1:2000) que ofrecen expresiones empíricas para obtener el tiempo de reverberación estructural. Otras (UNE-EN ISO 10848-1:2007) ofrecen un procedimiento detallado para determinar experimentalmente la diferencia de niveles de velocidad y el tiempo...
The Journal of the Acoustical Society of America, 2008
layers composing it. These types of devices are composed by monolithic glass and an intermediate ... more layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.
Microfluidic devices, also known as Lab on a Chip, are currently facing an increasing demand espe... more Microfluidic devices, also known as Lab on a Chip, are currently facing an increasing demand especially in the fine chemistry sector such as pharmaceutical or food industry. They can exhibit significant advantages over classical reactors because the reaction conditions in the microchannels noticeably differ from those in large-scale reactors. However, possible drawbacks of microreactors are inefficient reactant mixing due to the predominance of laminar flow and clogging (when solid-forming reactions are performed or solid catalyst suspensions are used). The use of ultrasonic irradiation has been successfully implemented not only to prevent these problems because of its well-known mixing and particle-dispersion effects, but also because of mass transport enhancement or potential solid catalyst reactivation. Several configurations have been used for this purpose ranging from immersion of the capillaries in ultrasonic baths or cavitation tubes (Figure 1), to the integration of miniatur...
Abstract It has been studied the sensitivity of the technique of intermodulation of ultrasonic wa... more Abstract It has been studied the sensitivity of the technique of intermodulation of ultrasonic waves to detect different damage states of concrete due to embedded steel corrosion. Accelerated corrosion tests have been conducted on reinforced cement mortar specimens, while monitoring the appearance and width evolution of visible surface cracks and performing intermodulation measurements. It has been established a statistically acceptable “upper control limit” for the initial (undamaged) Intensity Modulation Ratio (R) values. After subjecting the samples to the corrosion tests, it was observed that the greater the degree of damage, the higher the value ranges and the variability degree of R.
Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 2015
This paper describes the process undertaken to analyze numerically the vibrational behavior of th... more This paper describes the process undertaken to analyze numerically the vibrational behavior of the moving assembly of a dynamic loudspeaker with double bottom suspension and in the absence of the above one using the finite element method (FEM). The study focuses on the low frequency range. Model calibration was performed based on experimental measurements of the resonance frequency and diaphragm displacement. The importance of the participation factors associated to the excitation force and the changes produced in these when unbalanced forces are introduced are emphasized. The analysis also provides data to decide on the distance between suspensions, their optimal number of folds and the placement of the lead wires, parameters of great interest on the design of this type of loudspeakers.
2011 8th International Symposium on Wireless Communication Systems, 2011
ABSTRACT This paper proposes a novel framework for the cross-layer design and optimization of wir... more ABSTRACT This paper proposes a novel framework for the cross-layer design and optimization of wireless networks based on the use of discrete time Markov chains (DTMC) jointly modeling the PHY layer and MAC sublayer. The QoS performance at the DLC layer is included through a multidimensional DTMC jointly describing the statistical behavior of the arrival process, the queuing system and the PHY/MAC layers. A cross-layer design based on the DTMC analytical model is proposed. This cross-layer scheme aims at maximizing the average throughput of the system with constraints on the maximum tolerable average packet loss and delay.
Evaluation of the Simrad EY-500 echosounder for the population control of gilthead seabream Sparu... more Evaluation of the Simrad EY-500 echosounder for the population control of gilthead seabream Sparus auratus Linnaeus, 1758 cages. The use of the Simrad EY-500 echosounder in the field of marine aquaculture, particularly in the control of gilthead seabream Sparus auratus Linnaeus, 1758 populations, is evaluated. As a first approach to the problem, the suitability of the echosounder's physical properties (transducer
ABSTRACT This paper presents a numerical model based on the Method of Fundamental Solutions (MFS)... more ABSTRACT This paper presents a numerical model based on the Method of Fundamental Solutions (MFS) for the computational analysis of acoustic horns. The model is here presented in detail for 2D and axisymmetric problems, and it is based on the use of two sub-regions, one of them containing the acoustic horn itself, and the other simulating a semi-infinite space with perfectly reflecting boundary. The proposed model is tested against well established methodologies, such as the BEM and the FEM, and it is shown to provide accurate results. Besides its numerical verification, application examples concerning the evaluation of horn directivity are shown, including non-trivial geometrical configurations. Comparison with experimental measurements of the horn directivity at different frequencies reveals a very good match between theoretical and laboratorial results, and thus indicates that the proposed approach can be an interesting tool in the analysis of acoustic horns.
The Transfer Function (TF) relates the structure-borne noise level of the hull with the Underwate... more The Transfer Function (TF) relates the structure-borne noise level of the hull with the Underwater Radiated Noise (URN). Therefore, the acoustic noise generated by the vibrations of the hull of a ship could be estimated from real measurements of the structure-borne noise levels of the hull by applying the TF in real time. This function depends on the material of the hull of the ship. In this paper, real measurements of the structure-borne noise level of the hull and URN of two ships constructed of steel and Glass fiber Reinforced Plastics (GRP) are used to estimate the TF of the hull.
In this paper an alternative procedure to vibro-acoustics study of beam-type structures is presen... more In this paper an alternative procedure to vibro-acoustics study of beam-type structures is presented. With this procedure, it is possible to determine the resonant modes, the bending wave propagation velocity through the study of the radiated acoustic field and their temporal evolution in the frequency range selected. As regards the purely experimental aspect, it is worth noting that the exciter device is an actuator similar to is the one employed in distributed modes loudspeakers; the test signal used is a pseudo random sequence, in particular, an MLS (Maximum length Sequence), facilitates post processing. The study case was applied to two beam-type structures made of a sandstone material called Bateig. The experimental results of the modal response and the bending propagation velocity are compared with well-established analytical solution: Euler-Bernoulli and Timoshenko models, and numerical models: Finite Element Method-FEM, showing a good agreement.
Journal of the Acoustical Society of America, May 1, 2008
layers composing it. These types of devices are composed by monolithic glass and an intermediate ... more layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.
ANNALS OF THE ORADEA UNIVERSITY. Fascicle of Management and Technological Engineering., 2010
The object of the present work is to make a contribution to the quantification of the vibration b... more The object of the present work is to make a contribution to the quantification of the vibration behavior of the walls of two loudspeaker prototypes mounted in closed boxes, made of different materials. Using the finite elements method, a coupled fluid-structure numerical model of a loudspeaker-box system was implemented. The numerical model was calibrated from the experimental results obtained on a real model by means of modal analysis, vibration and pressure measurements. The conclusion is that the sonorous response of the system is affected by the vibration behavior of the box and its material.
There are many different types of sound absorbent materials. Nowadays, some simple models are use... more There are many different types of sound absorbent materials. Nowadays, some simple models are used to characterize these materials. These models are based on empirical equations obtained from measured data. The models are only valid for the studied materials. In the references there are different empirical models to predict the behaviour of some materials. In this investigation, a study of the behaviour of these simple models has been carried out, and some empirical equations for several sound absorbent materials have been proposed.
ABSTRACT In the present work, a three-dimensional (3D) formulation based on the method of fundame... more ABSTRACT In the present work, a three-dimensional (3D) formulation based on the method of fundamental solutions (MFS) is applied to the study of acoustic horns. The implemented model follows and extends previous works that only considered two-dimensional and axisymmetric horn configurations. The more realistic case of 3D acoustic horns with symmetry regarding two orthogonal planes is addressed. The use of the domain decomposition technique with two interconnected sub-regions along a continuity boundary is proposed, allowing for the computation of the sound pressure generated by an acoustic horn installed on a rigid screen. In order to reduce the model discretization requirements for these cases, Green’s functions derived with the image source methodology are adopted, automatically accounting for the presence of symmetry conditions. A strategy for the calculation of an optimal position of the virtual sources used by the MFS to define the solution is also used, leading to improved reliability and flexibility of the proposed method. The responses obtained by the developed model are compared to reference solutions, computed by well-established models based on the boundary element method. Additionally, numerically calculated acoustic parameters, such as directivity and beamwidth, are compared with those evaluated experimentally.
... Localización: V Jornades de Xarxes d¿Investigació en Docència Universitària [Recurso electrón... more ... Localización: V Jornades de Xarxes d¿Investigació en Docència Universitària [Recurso electrónico]: V Jornadas de Redes de Investigación en Docencia Universitaria. / Marcos IglesiasMartínez ( aut. ), Francesc Pastor Verdú ( aut. ), 2007, ISBN 978-84-690-77238 , pág. 27; ...
En los sistemas de reproducción sonora es habitual la utilización de altavoces dinámicos. Sin emb... more En los sistemas de reproducción sonora es habitual la utilización de altavoces dinámicos. Sin embargo, en aplicaciones específicas, puede ser necesaria y/o conveniente la utilización de altavoces alternativos con superficies planas como diafragma, como los electrostáticos o los basados en la tecnología NXT c. Estos altavoces generan el campo acústico mediante la vibración de una superficie rectangular. Se puede suponer, en una primera aproximación, que todos los puntos sobre su superficie se mueven con la misma amplitud y fase. En este trabajo se analiza el comportamiento directivo de este tipo de superficies para la generación del campo acústico y se simula su comportamiento, comparándolo con medidas experimentales.
La evaluación del ruido transmitido por flancos en edificación es esencial para el estudio del ai... more La evaluación del ruido transmitido por flancos en edificación es esencial para el estudio del aislamiento a ruido aéreo. Desde el punto de vista numérico, para la determinación de las transmisiones laterales es necesario conocer un parámetro conocido como índice de reducción vibracional. Para obtener este parámetro con el objetivo de conocer el comportamiento acústico de todo el conjunto constructivo, es necesario conocer la diferencia de niveles de velocidad y el tiempo de reverberación estructural. Indeterminaciones bien en la diferencia de niveles de velocidad, bien en el tiempo de reverberación estructural supondrán desviaciones en la determinación del aislamiento global de todo el conjunto constructivo. Existen normativas (UNE EN 12354-1:2000) que ofrecen expresiones empíricas para obtener el tiempo de reverberación estructural. Otras (UNE-EN ISO 10848-1:2007) ofrecen un procedimiento detallado para determinar experimentalmente la diferencia de niveles de velocidad y el tiempo...
The Journal of the Acoustical Society of America, 2008
layers composing it. These types of devices are composed by monolithic glass and an intermediate ... more layers composing it. These types of devices are composed by monolithic glass and an intermediate muffling layer usually made of PVB. In this study, we present a method to find the mechanical constants of PVB in laminated glasses. Mechanical constants characterization in these materials is studied using a model-based inverse problem and the data obtained from an ultrasonic transmission setup: a numerical simulation of the system is proposed using a lineal finite elements model of the ultrasonic propagation on the multilayered solid. Parameters are obtained by minimizing divergences between experimental and numerically predicted waveform.
Microfluidic devices, also known as Lab on a Chip, are currently facing an increasing demand espe... more Microfluidic devices, also known as Lab on a Chip, are currently facing an increasing demand especially in the fine chemistry sector such as pharmaceutical or food industry. They can exhibit significant advantages over classical reactors because the reaction conditions in the microchannels noticeably differ from those in large-scale reactors. However, possible drawbacks of microreactors are inefficient reactant mixing due to the predominance of laminar flow and clogging (when solid-forming reactions are performed or solid catalyst suspensions are used). The use of ultrasonic irradiation has been successfully implemented not only to prevent these problems because of its well-known mixing and particle-dispersion effects, but also because of mass transport enhancement or potential solid catalyst reactivation. Several configurations have been used for this purpose ranging from immersion of the capillaries in ultrasonic baths or cavitation tubes (Figure 1), to the integration of miniatur...
Abstract It has been studied the sensitivity of the technique of intermodulation of ultrasonic wa... more Abstract It has been studied the sensitivity of the technique of intermodulation of ultrasonic waves to detect different damage states of concrete due to embedded steel corrosion. Accelerated corrosion tests have been conducted on reinforced cement mortar specimens, while monitoring the appearance and width evolution of visible surface cracks and performing intermodulation measurements. It has been established a statistically acceptable “upper control limit” for the initial (undamaged) Intensity Modulation Ratio (R) values. After subjecting the samples to the corrosion tests, it was observed that the greater the degree of damage, the higher the value ranges and the variability degree of R.
Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 2015
This paper describes the process undertaken to analyze numerically the vibrational behavior of th... more This paper describes the process undertaken to analyze numerically the vibrational behavior of the moving assembly of a dynamic loudspeaker with double bottom suspension and in the absence of the above one using the finite element method (FEM). The study focuses on the low frequency range. Model calibration was performed based on experimental measurements of the resonance frequency and diaphragm displacement. The importance of the participation factors associated to the excitation force and the changes produced in these when unbalanced forces are introduced are emphasized. The analysis also provides data to decide on the distance between suspensions, their optimal number of folds and the placement of the lead wires, parameters of great interest on the design of this type of loudspeakers.
2011 8th International Symposium on Wireless Communication Systems, 2011
ABSTRACT This paper proposes a novel framework for the cross-layer design and optimization of wir... more ABSTRACT This paper proposes a novel framework for the cross-layer design and optimization of wireless networks based on the use of discrete time Markov chains (DTMC) jointly modeling the PHY layer and MAC sublayer. The QoS performance at the DLC layer is included through a multidimensional DTMC jointly describing the statistical behavior of the arrival process, the queuing system and the PHY/MAC layers. A cross-layer design based on the DTMC analytical model is proposed. This cross-layer scheme aims at maximizing the average throughput of the system with constraints on the maximum tolerable average packet loss and delay.
Evaluation of the Simrad EY-500 echosounder for the population control of gilthead seabream Sparu... more Evaluation of the Simrad EY-500 echosounder for the population control of gilthead seabream Sparus auratus Linnaeus, 1758 cages. The use of the Simrad EY-500 echosounder in the field of marine aquaculture, particularly in the control of gilthead seabream Sparus auratus Linnaeus, 1758 populations, is evaluated. As a first approach to the problem, the suitability of the echosounder's physical properties (transducer
ABSTRACT This paper presents a numerical model based on the Method of Fundamental Solutions (MFS)... more ABSTRACT This paper presents a numerical model based on the Method of Fundamental Solutions (MFS) for the computational analysis of acoustic horns. The model is here presented in detail for 2D and axisymmetric problems, and it is based on the use of two sub-regions, one of them containing the acoustic horn itself, and the other simulating a semi-infinite space with perfectly reflecting boundary. The proposed model is tested against well established methodologies, such as the BEM and the FEM, and it is shown to provide accurate results. Besides its numerical verification, application examples concerning the evaluation of horn directivity are shown, including non-trivial geometrical configurations. Comparison with experimental measurements of the horn directivity at different frequencies reveals a very good match between theoretical and laboratorial results, and thus indicates that the proposed approach can be an interesting tool in the analysis of acoustic horns.
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Papers by J. Ramis