Jesús Carbajo

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• PhD
• Associate Professor at University of Alicante

Emotional communication is a multi-modal phenomenon involving posture, gestures, facial expressions, and the human voice. Affective states systematically modulate the acoustic signals produced during speech production through the laryngeal muscles via the central nervous system, transforming the acoustic signal into a means of affective transmissio...

Noise pollution negatively impacts people’s mental and physiological health. Unfortunately, not only is noise present in hospital environments, but its level frequently exceeds recommended thresholds. The efficacy of passive acoustic absorbers in reducing indoor noise in these scenarios has been well-documented. Conversely, given their inorganic co...

Dynamic stiffness is a parameter of great importance for the assessment of the sound insulation properties of resilient materials commonly used under floating floors in dwellings. This work proposes a simplified approach that relies on an electro-mechanical circuit model for the determination of this parameter using a two-degree-of-freedom system o...

Variable acoustics systems are promising engineering developments for multi-purpose rooms and workspaces in many buildings. However, due to space requirements associated with most of the tuning devices used for that purpose, these solutions are hardly adopted in practice. In this work, two innovative tunable sound absorbers that cope with this draw...

Shipping traffic is recognised as the main man-noise source of the anthropogenic noise generated in the marine environment. The underwater acoustic pollution is increased due to the increment of the human activity at seas supposing a threat for marine habitats. The ship as acoustic source must be understood and controlled to manage the maritime are...

Anthropogenic noise is a growing threat to marine life due to the incrementation of human activity in the marine environment. In Europe, the Directive 2008/56/EC of the European Parliament and of the Council was published with the aim of establishing a framework for community action in the field of marine environmental policy. The directive introdu...

Several porous materials, especially natural fibres and polyurethane foams, are frequently used as sound absorbers in multiple noise reduction applications. Notwithstanding their excellent absorption performance, these materials usually lack the structural strength and fire resistance required for use in aggressive environments or situations requir...

The dynamic elastic modulus is an important parameter for the study of solid mechanical elements. Even though there exist several well-established standardized methods that allow determining this parameter under a state of simple stresses, some of these may require sophisticated laboratory equipment or involve the use of multiple devices (impulser,...

An important challenge for acoustic engineers in room acoustics design is related to the acoustic performance of multi-purpose auditoriums, which are typically designed to suit several performance requirements. With this intent, the analysis of several scenarios is usually performed individually, and then an acceptable solution, that may be adapted...

Using macro-perforations in a generic porous media may not only make the resonance frequency of a rigidly backed sound absorber lower but also its sound absorption amplitude increase. Given the rise of 3D-printing in the field of acoustic materials over the last years, it turns out of great interest to explore the possibilities of this technology o...

A relatively new concept of sound absorption herein denominated as Metaporous concrete is presented, consisting of a porous concrete-based sound absorber in which different acoustic resonators are embedded. Two finite element models were implemented, using the fluid-equivalent theory to describe Metaporous concrete solutions. A Helmholtz resonator,...

Many different solutions exist to improve the low-frequency sound absorption performance of acoustic resonators, extending or coiling up space into the resonator being some of the most widespread. In this context, modern additive manufacturing processes pose a new scenario in which these devices can be engineered to yield outstanding acoustic prope...

Low-frequency airborne noise reduction is an issue of major concern in most practical cases due to the limiting space constraints. The applicability of acoustic resonators that not only work in this frequency range but can also be tuned is of great interest in many noise control applications such as muffler devices, noise barriers, or building isol...

The use of porous concrete solutions with lightweight aggregates has become increasingly common in noise control due to their versatility in exterior and interior applications. In this work, samples of porous consolidated concrete with aggregates of expanded clay were produced, in order to study the influence of the grain size, thickness and water/...

Viscoelastic layers under floating floors are often used to reduce impact sound. A standardized dynamic stiffness test is routinely used to estimate the performance of a layer as an impact sound isolator. During the test, a material sample is placed between a load plate and a motionless rigid foundation. In this work, equations that provide a usefu...

The acoustic characterization of porous materials with rigid solid frame plays a key role in the prediction of the acoustic behavior of any dynamic system that incorporates them. In order to obtain an accurate prediction of its frequency-dependent response, a suitable choice of the parametric models for each material is essential. However, such mod...

Some of the most extended approaches to widen the sound absorption bandwidth of perforated panel absorbers are the use of different cavity depths or multi-layer arrangements. Unfortunately, these solutions are rarely adopted in practice because of the technical installation difficulties or the large space requirements. This work explores an alterna...

Acoustic meta-surfaces are periodic structures commonly realised using sub-wavelength sized resonators. One of their possible applications is in noise control where they can be applied to create very compact sound absorbers. Numerical modelling and characterization of meta-surfaces require the inclusion of acoustic viscous and thermal dissipation e...

Noise abatement provided by acoustic metamaterials is one of the peculiar features presented by these remarkable materials. In fact, the use of local resonant elements and their periodic distribution in the form of so-called sonic crystal arrangements have demonstrated to enhance those attenuation properties. In this work, the authors present an ef...

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 experime...

Heterogeneous perforated panels are of great interest as sound absorbers, while achieving a smart high-end decoration in meeting rooms, showrooms, conference halls, etc. However, their uneven nature may pose a difficulty when trying to predict their acoustic performance using traditional impedance models. This work explores the use of four differen...

Grooved acoustic panels are rigid plates consisting of an interconnected network of periodically arranged slits and circular holes. These devices are traditionally used as resonant absorbers in building acoustics. This paper presents a model to predict the acoustic properties of such absorbers. For this purpose, the classical Johnson-Champoux-Allar...

Perforated concrete shows nowadays a high potential for many construction and building engineering applications. This work is devoted to the analysis of the acoustic properties of perforated concrete made from arlite lightweight aggregates. Concrete produced from these materials is an environmentally friendly alternative to traditional materials an...

Electric Vehicles (EVs) are expected to be equipped with Acoustic Vehicle Alerting System (AVAS) that effectively allow vulnerable pedestrians to detect from which direction EVs are approaching. In this context, directional sound sources have been proposed to provide an effective warning sound where necessary, without being excessively loud in othe...

The use of sustainable materials is becoming a common practice for noise abatement in building and civil engineering industries. In this context, many applications have been found for porous concrete made from lightweight aggregates. This work investigates the acoustic properties of porous concrete made from arlite and vermiculite lightweight aggre...

Most of the analytical models devoted to determine the acoustic properties of a rigid perforated panel consider the acoustic impedance of a single hole and then use the porosity to determine the impedance for the whole panel. However, in the case of not homogeneous hole distribution or more complex configurations this approach is no longer valid. T...

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 regardi...

Resumen En este trabajo se describe el proceso llevado a cabo para analizar numéricamente mediante el método de los elementos finitos (MEF) el comportamiento vibratorio del conjunto móvil de un altavoz dinámico de bobina con doble suspensión inferior y en ausencia de la superior. El estudio se centra en el rango de baja frecuencia. El calibrado del...

Sonic crystals are a relatively recent concept that is being explored for different applications. Several types of models exist in literature for their analysis, although in many cases they consider their elements to be rigid. In this work, the authors propose a hybrid numerical-analytical model based on the Method of Fundamental Solutions (MFS) to...

The study of periodic structures, namely sonic crystals, for sound attenuation purposes has been a topic of intense research in the last years. Some efficient methods are available in literature to solve the problem of sound propagation in the presence of this kind of structures such as those based in the Multiple Scattering Theory (MST) or the Fin...

In the present paper, a methodology is proposed for obtaining empirical equations describing the sound absorption characteristics of an absorbing material obtained from natural fibers, specifically from coconut. The method, which was previously applied to other materials, requires performing measurements of air-flow resistivity and of acoustic impe...

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 sp...

In this work the procedure followed to study the interaction between the mid and high frequency radiating systems of a coaxial loudspeaker is explained. For this purpose a numerical Finite Element model was implemented. In order to fit the model, an experimental prototype was built and a set of experimental measurements, electrical impedance, and p...

The present paper addresses the analysis of structural vibration transmission in the presence of struc- tural joints. The problem is tackled from a numerical point of view, analyzing some scenarios by using finite element models. The numerical results obtained making use of this process are then compared with those evaluated using the EN 12354 stan...

This work analyses some of the issues related with small size direct radiation loudspeakers design with the main goal of achieving high SPL (Sound Pressure Level). In order to reach it, large diaphragm displacements are needed. Structural dynamic behaviour of the moving assembly must be emphasized. With the aid of a numerical model implemented with...

In this paper we describe some results that have led to the improvement of the response of an Air Motion Transformer loudspeaker. First, it is noteworthy that it has been found an approximate analytical solution to the differential equations system that governs the behavior of the moving assembly of this type of transducer, being this valid when th...

In this work we present some results of an experimental study carried out to determine the vibratory response of a structure of concrete. This structure has a soil of 10 cm of thickness. On this base, four vertical elements rise forming a cross centered with the slab, thus the space is divided in four equal parts. Two types of excitation have been...

In this work we propose a methodology to characterize laminated glass, and, this way like to predict the acoustic isolation of this type of constructive elements. Taking as starting point the measures of function of transfer acceleration-force for monolithic bars of glass and of laminated glass, there is applied a numerical inverse method to determ...