Rubén Picó

• Dr
• Researcher at Polytechnic University of Valencia

Acoustic signals, which have been utilized for decades in the spatial localization of objects, have found applications in fields as diverse as sonar for underwater navigation, communication, and object detection. Traditional methods often rely on arrays of transducers, which necessitate the use of expensive hardware and processing algorithms. An em...

Resumen Desde la década de 1910, las señales acústicas se han utilizado para la localización espacial de objetos, como en el SONAR, y en diversas aplicaciones de localización de fuentes sonoras en el aire, incluyendo sistemas de seguridad. Estos sistemas suelen emplear arrays de transductores acústicos en configuraciones geométricas variadas, lo cu...

The use of acoustic signals to locate objects in space has evolved significantly, highlighting techniques such as SONAR. An innovative alternative are Acoustic Leaky-Wave Antennas (ALWAs), which, inspired by electromagnetic Leaky-Waves Antennas (LWAs), uses a single transducer to emit directional beams by changing the operating frequency, offering...

In an experimental investigation, the development of sonic crystal noise barriers (SCNBs) is undertaken to address the issue of train brake noise (TBN), focusing on the use of local resonances in scatterers of sonic crystals. Recent research has shown that the inclusion of cavity resonators in the crystal scatterers allows for the modification of t...

The study of periodic structures and their dispersive properties has led to the inclusion of resonances in their elements, in most cases Helmholtz resonators to analyze the interaction of both phenoma. In particular, in the case of sound crystals (SC) the resonators are embedded in the scatterer, and it is necessary to consider the design of these...

Helmholtz resonators (HRs) have the advantage of extending and improving their insulating capacity when used as scatterers in noise barriers made of periodic media, such as sonic crystals (SCs). However, the interaction between multiple Bragg scattering and local resonance phenomena can increase or decrease the insulation of the barrier depending o...

This broad review summarizes recent advances and “hot” research topics in nanophononics and elastic, acoustic, and mechanical metamaterials based on results presented by the authors at the EUROMECH 610 Colloquium held on April 25–27, 2022 in Benicássim, Spain. The key goal of the colloquium was to highlight important developments in these areas, pa...

The implementation of metamaterials in acoustic barriers has meant a great improvement in many of their properties and a wide range of possibilities for design and adaptation to different cases of noise study. However, in most of the cases, the study of the acoustic behaviour of these devices is limited to the case of normal incidence. The main pur...

The perfect absorption of bending waves by thermally tunable subwavelength absorbers is analytically and experimentally demonstrated in this work for a reflection problem in beams. These absorbers are local resonators located at the end of a semi-infinite beam and consist of thin blades covered with a layer of Shape Memory Polymer (SMP), the stiffn...

A fibrous material is characterized by its fineness, flexibility and high length/fineness ratio and it is used to reduce noise in indoor rooms due to their porous structure. The aim of this work is focused on investigating the structure of two different fibers (acrylic and polyester) from the analysis of the macrostructural parameters, such as fine...

Acoustic screens based on sonic crystals constitute one of the most promising technological bets of recent years in the field of environmental acoustics. Sonic crystals are defined as new materials formed by arrays of acoustic scatterers embedded in air. The design of these screens is made using powerful simulation models that provide reliable resu...

Textile materials used without any other structures show low absorption throughout the operating frequency range, and they are currently used for interior decoration. These fabrics can play an important role in the development of acoustic materials considering folding techniques in the design phase. The folding of a cotton fabric not only affects t...

The optimal absorption of flexural energy by the critical coupling of a locally resonant grating embedded in a thin plate is reported in this work for the reflection and transmission problems. The grating is made of a 1D-periodic array of local resonators. A viscoelastic coating is also placed on top of each resonator to control the intrinsic losse...

No PDF available ABSTRACT Acoustic screens based on sonic crystals constitute one of the most promising technological bets of recent years in the field of environmental acoustics. Sonic crystals are defined as new materials formed by arrays of acoustic scatterers embedded in air. The design of these screens is made using powerful simulation models...

Recent trends in waste management have initiated interest in recycled materials for sound absorption applications. The present paper studies the possibility of paper sludge to be recycled as material for sound absorption applications. Paper sludge (PS) is the water treatment waste, produced during paper production. Two different methods were studie...

In this work, we numerically investigate the diffraction management of longitudinal elastic waves propagating in a two-dimensional metallic phononic crystal. We demonstrate that this structure acts as an “ultrasonic lens”, providing self-collimation or focusing effect at a certain distance from the crystal output. We implement this directional prop...

This work presents the prediction of noise generated during the launch of space rockets. A semi- empirical model was applied, using as input data the physical and geometric characteristics of the jet of gases propelled by the rocket, which acts as the primary source of noise. The model is based on the one originally proposed by Eldred back in 1971...

An Acoustic Black Hole (ABH) in a one-dimensional (1D) beam is a passive vibration damping device based on a local reduction of the beam thickness attached to a thin layer of attenuating material. This work aims at revisiting the ABH effect by analysing the ABH trapped modes in the complex frequency plane. This analysis relies on an analytical mode...

We report a theoretical and experimental study of an array of Helmholtz resonators optimized to achieve both efficient sound absorption and diffusion. The analysis starts with a simplified 1D model where the plane wave approximation is used to design an array of resonators showing perfect absorption for a targeted range of frequencies. The absorpti...

The use of microcapsules is increasing in the textile industry and play an important role in the field of acoustical porous materials in order to adopt solutions for the control of noise. In this work, we present an experimental study of the acoustic effect of woven textile fabrics doped with microcapsules by using the padding technique. For this p...

The acoustic properties of recycled polyurethane foams are well known. Such foams are used as a part of acoustic solutions in different fields such as building or transport. This paper aims to seek improvements in the sound absorption of these recycled foams when they are combined with fabrics. For this aim, foams have been drilled with cylindrical...

We report a method to monitor the setting process of bone-graft substitutes (calcium sulphate) using ultrasonic backscattering techniques. Analyzing the backscattered fields using a pulse-echo technique, we show that it is possible to dynamically describe the acoustic properties of the material which are linked to its setting state. Several experim...

This work envisages a detailed study of two-dimensional defect localization and reconstruction, using laser generated ultrasound and its application as a remotely controlled non-destructive testing method. As an alternative to full ultrasonic or full optical approaches, we propose a hybrid configuration where ultrasound is generated by impact of la...

p>En este trabajo se desarrollan de forma numérica modelos empíricos que permiten conocer el comportamiento acústico de materiales utilizados en soluciones constructivas en la edificación. Este trabajo se engloba dentro del Máster Universitario en Ingeniería Acústica (MIA) de la Escuela Politécnica Superior de Gandía en la Universitat Politècnica d...

Nondestructive testing of metallic objects that may contain embedded defects of different sizes is an important application in many industrial branches for quality control. Most of these techniques allow defect detection and its approximate localization, but few methods give enough information for its 3D reconstruction. Here we present a hybrid las...

The limits of flexural wave absorption by open lossy resonators are analytically and numerically reported in this work for both the reflection and transmission problems. An experimental validation for the reflection problem is presented. The reflection and transmission of flexural waves in 1D resonant thin beams are analyzed by means of the transfe...

Non-destructive testing of metallic objects that may contain embedded defects of different sizes is an important application in many industrial branches for quality control. Most of these techniques allow defect detection and its approximate localization, but very few give enough information for its 3D reconstruction. Here we present a hybrid laser...

We report a method to monitor the setting process of bone-graft substitutes (calcium sulphate) using ultrasonic backscattering techniques. Analyzing the backscattered fields using a pulse-echo technique, we show that it is possible to dynamically describe the acoustic properties of the material which are linked to its setting state. Several experim...

The limits of flexural wave absorption by open lossy resonators are analytically and numerically reported in this work for both the reflection and transmission problems. An experimental validation for the reflection problem is presented. The reflection and transmission of flexural waves in 1D resonant thin beams are analyzed by means of the transfe...

Ultrasonic backscattering techniques are used to monitor the setting process of calcium sulfate. A 3.5 MHz frequency pulse-echo system is used to obtain the acoustic properties of a sample of calcium sulfate. The temperature of the sample and the rf-backscattering signal are measured every two seconds during the whole setting process (53 min; 1590...

El timple es un pequeño cordófono tradicional del archipiélago canario (región ultraperiférica del Reino de España). Por su morfología, es semejante al ukelele o al guitarró, pero difiereen que la parte trasera del timple es curva. En este trabajo de investigación se aborda el estudio del timple desde dos perspectivas: organológica y acústica. Para...

Aligned with current research efforts and industrial applications on nondestructive testing, in this work, a hybrid system combining remotely induced laser ultrasonics with conventional transducer detection is studied for defects detection in metallic parts. The processing of the induced acoustic emission waves is proposed to be approached by means...

A motivation for the study of reduced models like one-dimensional systems in Solid State Physics is the complexity of the full problem. In recent years our group has studied theoretically, numerically and experimentally wave propagation in lattices of nonlinearly coupled oscillators. Here, we present the dynamics of magnetically coupled pendula lat...

Articulation marks are used to indicate to the interpreter how notes should sound. In this work it is proposed a method for the description of the acoustic properties of sounds corresponding to different articulations of the transverse flute. For this purpose, we analyse acoustic signals recorded and interpreted with different symbols, simple and c...

Flexural waves are the main type of waves propagating in thin plates and play a relevant role in the eld of noise and vibration. In this work, the study of the conditions for the absorption of sound due to exural resonances is reported. Two systems composed of thin clamped aluminum square plates with an absorptive layer in contact are studied: (i)...

A lattice of repelling particles is a good model for studying certain properties that take place at atomic scale in Solid State Physics. In this chapter we study theoretically and experimentally the generation and propagation of kinks in such kind of systems. We propose a simple experimental setup consisting in an array of pendulums, having magnets...

The broadband reduction of the specular reflections by sonic crystals (SCs) is theoretically and experimentally reported in this work. The analysed system consists of a sound source radiating a SC made of acoustically rigid scatterers embedded in water partially covering an open cavity. By comparison with a reference flat reflector, we observe that...

This work is framed in the field of dentistry. The objective is to develop a non-destructive ultrasonic system for monitoring the process of Guided Bone Regeneration (GBR). The behavior of various aqueous solutions has been studied at different frequencies (0.5, 1, 5 and 7.5 MHz). Parameters such as SOS (Speed of Sound) and BUA (broadband ultrasoni...

We consider a lattice of nonlinearly coupled oscillators, where the masses interact with their nearest neighbors by repulsive forces. Such physical system is realized experimentally, with an array of cylindrical magnets (magnetic dipoles), forming a nearly one dimensional chain of masses coupled by its magnetic fields. The magnetic moments of neigh...

p>La enseñanza en el Máster de Ingeniería Acústica incluye contenido que requiere la modelización de sistemas acústicos de dos tipos: sistemas simples usando la teoría analítica y modelos complejos usando técnicas de simulación. En este trabajo, se describe un ejemplo de modelado de fuentes acústicas complejas mediante el método de los elementos fi...

Description of articulated sounds in flute by articulation marks. Recorded sounds and spectral analyze working through descriptors that offers a qualitative comprehension of them.

Propagation of mechanical waves in unidimensional systems is a fundamental part of physics, necessary for learning subjects such as acoustics and vibrations. The vibration of transverse waves in strings is the easiest case of elastic system. Usually, this is the first continuous elastic system in which students apply fundamental mathematical concep...

Los elevados niveles de presión acústica experimentados por cohetes espaciales y lanzaderas durante el despegue son debidos, entre otros factores, a la reflexión de las ondas de sonido en la plataforma de lanzamiento. Se propone el uso de cristales de sonido en la base de lanzamiento para reducir el efecto de las vibraciones inducidas por la onda d...

The propagation of nonlinear waves in a lattice of repelling particles is studied theoretically and experimentally. A simple experimental setup is proposed, consisting in an array of coupled magnetic dipoles. By driving harmonically the lattice at one boundary, we excite propagating waves and demonstrate different regimes of mode conversion into hi...

The propagation of nonlinear waves in a lattice of repelling particles is studied theoretically and experimentally. A simple experimental setup is proposed, consisting in an array of coupled magnetic dipoles. By driving harmonically the lattice at one boundary, we excite propagating waves and demonstrate different regimes of mode conversion into hi...

This work theoretically analyzes the sound absorption properties of a chirped multi-layer porous material including transmission, in particular showing the broad- band unidirectional absorption properties of the system. Using the combination of the impedance matching condition and the balance between the leakage and the intrinsic losses, the system...

Asymmetric propagation of acoustic waves is theoretically reported in a chirped phononic crystal made of the combination of two different nonlinear solids. The dispersion of the system is spatially dependent and allows the rainbow trapping inside the structure. Nonlinearity is used to activate the self-demodulation effect, which is enhanced due to...

Asymmetric propagation of acoustic waves is theoretically reported in a chirped phononic crystal made of the combination of two different nonlinear solids. The dispersion of the system is spatially dependent and allows the rainbow trapping inside the structure. Nonlinearity is used to activate the self-demodulation effect, which is enhanced due to...

This work theoretically analyzes the sound absorption properties of a chirped multi-layer porous material including transmission, in particular showing the broadband unidirectional absorption properties of the system. Using the combination of the impedance matching condition and the balance between the leakage and the intrinsic losses, the system i...

The acoustic pressure levels experienced by the spacecraft and launchers during the lift-off is due among other factor by the reflection of the sound waves on the launch pad. The acoustic load distribution in the area of the launcher depends on the geometric, mechanical and acoustic characteristics of the ground facilities. This work is intended to...

We discuss two possible regimes of solitary wave formation in acoustic layered media. In the weakly dispersive limit, KdV-type solitons are formed, consisting of broad pulses with a width much larger than the lattice periodicity. Such KdV solitons are shown to exist even far from the weakly dispersive conditions. On the other hand, in the strongly...

In this work, we studied numerically, analytically and experimentally the nonlinear dynamics for a chain of magnates. Propagation the second harmonic depends on the medium parameters and the excitation signal (amplitude and frequency). From the experimental results which have a good agreement with the theoretical results, several phenomena in nonli...

A resonant sonic crystal made of solid elastic clamped beams is experimentally analysed in this work. The sonic crystal studied in this work has three characteristics: (i) a low filling fraction, (ii) a high frequency Band Gap and (iii) resonant scatterers. Due to the properties (i) and (ii), the sonic crystal behaves as an equivalent fluid with ac...

From the acoustical point of view one of the most extreme events is the lift-off of a rocket. In such events, an enormous amount of energy is liberated in the form of acoustic waves that are reflected in the launch pad, coming back over the rocket and affecting both the rocket and the load contained in the fairing. Here we propose a possible soluti...

In this work we study numerically the existence of gap solitons in an acoustic media. To approach the problem a set of coupled-mode equations are given. In order to obtain a solitary wave in a real media, it is necessary of two phenomena, dispersion and nonlinearity. Acoustic media, usually can present nonlinearity but also low dispersions. To incr...

In this work, we studied numerically, analytically and experimentally the nonlinear dynamics of this system, in particular, harmonic generation and the balance between nonlinearity and dispersion. Three regimes have been explored exciting the chain, forcing the first pendulum with an harmonic force of long wavelength with respect to a and with such...

The understanding of phenomena that occurs in matter at micro-scale is a very complex task. For doing that, the best way to investigate such systems is simplifying the problem by creating a macro-scale model with nearly similar or equivalent parameters and conditions. For example, in the case of medical diagnosis, an ultrasound contrast (micro-bubb...

The formation of high-order Bessel beams by a passive acoustic device consisting of an Archimedes' spiral diffraction grating is theoretically, numerically and experimentally reported in this work. These beams are propagation-invariant solutions of the Helmholtz equation and are characterized by an azimuthal variation of the phase along its annular...

The formation of high-order Bessel beams by a passive acoustic device consisting of an Archimedes' spiral diffraction grating is theoretically, numerically and experimentally reported in this work. These beams are propagation-invariant solutions of the Helmholtz equation and are characterized by an azimuthal variation of the phase along its annular...

The propagation of intense acoustic waves in a one-dimensional phononic crystal is studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength, therefore Bragg effects su...

We report first-order Bessel beam formation by means of a novel passive acoustic device. The scattering of plane waves by a spiral grating leads to the creation of an acoustic vortex with a pressure null on-axis. Numerical simulations and experimental results report the formation of an acoustic vortex in the near field as the phase presents a screw...

We report the nonlinear focusing of ultrasonic waves by an axisymmetric diffraction grating immersed in water. In the linear regime, the system presents high focal gain (32 dB), with a narrow beam-width and intense side lobes as it is common in focusing by Fresnel-like lenses. Activating the nonlinearity of the host medium by using high amplitude i...

We investigate the propagation of nonlinear waves in a periodic lattice of magnetically coupled oscillators. Experiments show that higher harmonics of the forcing frequency are generated and propagate along the chain. It is shown that at high frequencies harmonic generation is strongly influenced by the dispersive properties of the chain. Experimen...

Some effects related to high amplitude acoustic waves in periodic media are investigated. The combined action of nonlinearity (harmonic generation) and periodicity (different propagation velocities and attenuation for the different harmonics) results in novel and unexpected phenomena, with respect to the linear problem, and opens the door to new me...

Water-droplet suspension has been used as a primary noise attenuation mechanism in the context of launching of space vehicles, where other attenuation mechanisms are hardly applicable. In this work, we present an experimental study of the attenuation properties of the sound transmitted through a multilayer structure of a saturated gas-vapor-droplet...

We report the propagation of high-intensity sound beams in a sonic crystal, under self-collimation or reduced-divergence conditions. The medium is a fluid with elastic quadratic nonlinearity, where the dominating nonlinear effect is harmonic generation. The conditions for the efficient generation of narrow, non-diverging beam of second harmonic are...

The propagation of intense acoustic waves in a periodic medium (sonic crystal) is numerically studied. The medium consists in a structured fluid, formed by a periodic array of fluid layers with alternating linear acoustic properties and quadratic nonlinearity coefficient. The spacing between layers is of the order of the wavelength; therefore Bragg...

En este trabajo se presenta un estudio experimental en el que se analizan las propiedades de atenuación del sonido transmitido a través de una estructura multicapa, en la que cada uno de los elementos consiste en una lámina formada por gotas de agua con una distribución de tamaños alrededor de un valor medio. Para ello, se ha diseñado un sistema de...

We propose a periodic structure that behaves as a fluid–fluid composite for sound waves, where the building blocks are clusters of rigid scatterers. Such building-blocks are penetrable for acoustic waves, and their properties can be tuned by selecting the filling fraction. The equivalence with a fluid–fluid system of such a doubly periodic composit...

We study the propagation of waves in a periodic array of absorbing layers. We report an anomalous increase of wave transmission through the structure related to a decrease of the absorption around the Bragg frequencies. The effect is first discussed in terms of a generic coupled wave model extended to include losses, and its predictions can be appl...

The enhancement of sound inside a two dimensional exponentially chirped crystal during the soft reflections of waves is experimentally and theoretically explored in this work. The control of this enhancement is achieved by a gradual variation of the dispersion in the system by means of a chirp of the lattice constant. The sound enhancement is produ...

En este trabajo se presenta un estudio experimental en el que se analizan las propiedades de atenuación del sonido transmitido a través de una estructura multicapa, en la que cada uno de los elementos consiste en una lámina formada por gotas de agua con una distribución de tamaños alrededor de un valor medio. Para ello, se ha diseñado un sistema de...

A high amplitude acoustic wave travelling in a fluid develops higher harmonics as it propagates through the medium. In a homogeneous fluid, such nonlinearly generated harmonics grow during propagation because of the lack of dispersion. On the other hand, periodic acoustic media such as 1D layered media, or 2D sonic crystals, are known to introduce...

Artworks are a valuable part of the World's cultural and historical heritage. Conservation and authentication of authorship are important aspects to consider in the protection of cultural patrimony. In this paper we present a novel application of a well-known method based on the phase-shift analysis of an ultrasonic signal, providing an integrated...

We report Bessel-like beam formation of acoustic waves by means of an axisymmetric grating of rigid tori. The results show that the generated beam pattern is similar to that of Bessel beams, characterized by elongated non-diffracting focal spots. A multiple foci structure is observed, due to the finite size of the lens. The dependence of the focal...

We present the design of a structured material supporting complete absorption of sound with a broadband response and functional for any direction of incident radiation. The structure which is fabricated out of porous lamellas is arranged into a low-density crystal and backed by a reflecting support. Experimental measurements show that strong all-an...

Target phase information in acoustic backscattering has been proposed as an additional target identification parameter. In general, incorporating phase into sonar signal processing for acoustical oceanography could aid in the assessment of fish populations and ecosystems. In this work, a broadband sonar system calibrated in amplitude and phase is u...

The symmetry matching between the source and the lens results in fundamental interest for lensing applications. In this work, we have modeled an axisymmetric gradient index (GRIN) lens made of rigid toroidal scatterers embedded in air considering this symmetry matching with radially symmetric sources. The sound amplification obtained in the focal s...

A sound diffuser is proposed based on sonic crystals, structures formed by a periodic distribution of cylindrical scatterers in a host medium, which is usually air. The diffuser is a so-called biperiodic structure, as formed by two arrays of sonic crystals with slightly different periodicities. Large diffusivity at low frequencies is achieved when...

The symmetry matching between the source and the lens results of fundamental interest for lensing applications to amplify the intensity at the focal spot. In this work we have designed and both theoretically and experimentally reported an axisymmetric 3D metamaterial gradient index lens (GRIN) made of rigid toroidal scatterers embedded in air. By a...

En este trabajo se analizan las propiedades de propagación de las ondas sonoras en un sistema con simetría axial cuyos dispersores son toroides rígidos. El objetivo es el diseño, construcción y caracterización de un sistema para la focalización eficiente de las ondas mediante elementos pasivos (lente acústica). Mediante simulaciones numéricas en el...

En este trabajo se presenta un modelo matemático que describe el comportamiento dinámico de una cerámica piezoeléctrica comercial vibrando en modo espesor. Dicho modelo resuelve, mediante diferencias finitas, las ecuaciones piezoeléctricas que relacionan los fenómenos mecánicos y eléctricos que se producen en este tipo de materiales, y simula el co...