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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 drawback are proposed, one consisting of rotating perforated panels and the other being a panel with an iris-type aperture. Compared with conventional perforated panel sound absorbers, the designed solutions yield a variable open area ratio system, whose configuration allows tuning the absorption bandwidth without misusing space. To assess their sound absorption coefficient, impedance tube experiments were carried out following the standardized method described in ISO 10534-2 over specimens fabricated for this purpose using laser cutting and additive manufacturing technology. The results not only show their good sound absorption performance but also highlight their tuning capabilities. Complementarily, a model based on the ray tracing method was developed to evaluate the performance of these solutions in a case study room, for different occupancy levels, with the results supporting the previous assertions and revealing the improved intelligibility features when used in such scenarios. The proposed solutions, together with the prediction model, provide a feasible approach for the design and development of tunable sound absorbers in variable room acoustics.

La acústica submarina es crucial para entender el entorno marino y la vida acuática. Recientes estudios revelan que los peces son particularmente sensibles al movimiento de partículas en el agua, abarcando desplazamiento, velocidad y aceleración, más que a la presión sonora, especialmente en condiciones de campo cercano debido a las propiedades vectoriales del movimiento de partículas. Esta sensibilidad destaca la necesidad de evaluar cómo el ruido antropogénico, generado por actividades humanas como el tráfico marítimo y la exploración petrolera, afecta a la vida marina. Este tipo de ruido perjudica la comunicación, reproducción y supervivencia de las especies marinas. El estudio se centra en el desplazamiento de partículas generadas por fuentes sonoras submarinas y su relación con la presión sonora. Desarrollar sensores que midan este desplazamiento es esencial para comprender cómo las partículas se mueven en respuesta a ondas de presión en el entorno submarino. Esta investigación es vital para entender los efectos del ruido submarino en las especies y contribuir a su conservación. Con estos conocimientos, se pueden crear estrategias de mitigación para proteger la vida y los ecosistemas submarinos.

The damage identification of railway bridges poses a formidable challenge given the large variability in the environmental/operational conditions that such structures are subjected to along their lifespan. Within a research project devoted to the continuous monitoring of a real in-operation bridge, the Mascarat Viaduct in Alicante (Spain), this paper investigates the potential use of strain sensors and autoregressive (AR) modelling to extract highly sensitive damage features. The viaduct, built in the beginning of the 20th century, belongs to the TRAM line 9 in the province of Alicante (Spain). The viaduct is instrumented with a dense network of strain sensors and accelerometers for monitoring the structural response under train passages. As an initial exploratory investigation, and with the aim of developing a physics-based digital twin of the viaduct, this work presents an introductory numerical assessment of the potential use of strain measurements and AR models for fast damage identification. To this aim, a finite element model (FEM) of the viaduct has been developed to simulate the dynamic response of the viaduct under moving train loads. On this basis, a two-class damage classifier (damaged or non-damaged) is developed by exploiting time series of continuously identified AR parameters. The presented results and discussion evidence the usefulness of the proposed methodology, offering an unsupervised damage detection approach with minimum computational efforts.

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 of masses and springs. Unlike the method described in the standard ISO 9052-1, the proposed approach uses a single electrodynamic actuator both as an impulser and vibration sensor, thus reducing the instrumental requirements and yielding a more stable arrangement. By measuring the input electrical impedance of the mass-loaded actuator when coupled to a slab–material system it was possible to retrieve the mechanical mobility function thereof and thus obtain the dynamic stiffness of the material. Several materials were tested following the proposed approach, with results showing good agreement when compared to those obtained following the standardized procedure. In general, the preliminary research encourages the use of the proposed approach for characterization purposes.

[Abstract]: 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 of masses and springs. Unlike the method described in the standard ISO 9052-1, the proposed approach uses a single electrodynamic actuator both as an impulser and vibration sensor, thus reducing the instrumental requirements and yielding a more stable arrangement. By measuring the input electrical impedance of the mass-loaded actuator when coupled to a slab–material system it was possible to retrieve the mechanical mobility function thereof and thus obtain the dynamic stiffness of the material. Several materials were tested following the proposed approach, with results showing good agreement when compared to those obtained following the standardized procedure. In general, the preliminary research encourages the use of the proposed approach for characterization purposes.

La comunicación emocional es un fenómeno multimodal que afecta a la postura, los gestos, las expresiones faciales y la voz humana. En este contexto, los estados afectivos modulan sistemáticamente las señales acústicas emitidas en la producción del habla mediante los músculos laríngeos vía sistema nervioso central, transformando la señal acústica en un medio de transmisión afectivo. Diversos trabajos han analizado los parámetros acústico-emocionales de la voz humana, concluyendo que la calidad de voz, la frecuencia fundamental o el tono juegan un papel primordial en la expresión emocional. Paralelamente, un creciente número de estudios acumulan evidencia de la capacidad de las ondas mecánicas para afectar a la proliferación celular, poniendo de relieve el papel de las ondas mecánicas como agente biofísico. La presente investigación se centra en analizar los efectos de señales acústico-emocionales sobre la proliferación celular de la línea 661W y la expresión proteica. Para tal fin, se ha diseñado y calibrado un sistema de radiación electroacústico en el interior de una incubadora de CO2 y establecido un método de captación de la señal acústico-emocional. Resultados preliminares apuntan a la capacidad de señales acústico-emocionales para influir sobre la proliferación celular., Emotional communication is a multimodal phenomenon involving posture, gestures, facial expressions and the human voice. In this context, affective states systematically modulate the acoustic signals emitted in speech production through the laryngeal muscles via the central nervous system, transforming the acoustic signal into a means of affective transmission. Several studies have analyzed the acoustic-emotional parameters of the human voice, concluding that voice quality, fundamental frequency or pitch play a major role in emotional expression. In parallel, a growing number of studies accumulate evidence of the ability of mechanical waves to affect cell proliferation, highlighting the role of mechanical waves as a biophysical agent. The present investigation focuses on analyzing the effects of acoustic-emotional signals on 661W cell proliferation and protein expression. For this purpose, an electroacoustic radiation system has been designed and calibrated inside a CO2 incubator and a method of acoustic-emotional signal capture has been established. Preliminary results point to the ability of acoustic-emotional signals to influence cell proliferation.

El ruido submarino antropogénico es una amenaza creciente para la vida marina debido al incremento de la actividad humana en el medio marino. En Europa se publicó la Directiva 2008/56/CE del Parlamento Europeo y del Consejo con el objetivo de establecer un marco de actuación comunitaria en el ámbito de la política medioambiental marina. La directiva introduce la energía acústica submarina, tal y como se detalla en el Descriptor 11, como fuente contaminante, por lo que se hace necesario realizar la monitorización y seguimiento de los niveles acústicos en el entorno marítimo. Se establecen dos metodologías para determinar el nivel de contaminación acústica submarina; la monitorización mediante el despliegue de hidrófonos y la elaboración de paisajes o mapas sonoros. El primer método requiere un despliegue de larga duración lo que implica un alto coste por lo que la elaboración de mapas sonoros es una alternativa real para establecer los niveles acústicos en una demarcación marítima determinada. En el presente trabajo se presentan las necesidades y procesos necesarios para la elaboración de paisajes sonoros en el contexto del proyecto: Filling the gap: Thresholds assessment and impact beyond acoustic pressure level linked to emerging blue-growth activities (SONORA) referencia PCI2022-135081-2., Anthropogenic noise is a growing threat to marine life due to the increment 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 introduces underwater acoustic energy, as detailed in Descriptor 11, as a polluting source, which makes it necessary to monitor and follow the acoustic levels in the maritime environment. Two methodologies are established to determine the level of underwater pollution; monitoring through the deployment of hydrophones and the elaboration of landscapes or sound maps. The first method requires a long-term deployment, which implies a high cost, so the elaboration of sound maps is a real alternative to establish the noise levels in a given maritime area. This paper presents the requirements and processes needed for the elaboration of soundscapes in the context of the Project: Filling the gap: Thresholds assessment and impact beyond acoustic pressure level linked to emerging blue-growth activities (SONORA) reference PCI2022-135081-2.

El diseño de un altavoz para el medio marino implica afrontar diversos retos en comparación con el medio aéreo. La principal dificultad reside en la elevada impedancia acústica del agua, que genera una carga mucho mayor sobre el diafragma y, por tanto, por lo que se exige una mayor resistencia y adaptación a las variaciones de presión. Para ello, se necesita desarrollar un diafragma de gran rigidez y baja masa. Así mismo, se requiere un motor magnético muy potente aumentar el rendimiento y lograr un alto nivel de presión sonora. Además, se debe garantizar un aislamiento efectivo entre la onda frontal y la onda posterior, mediante la incorporación de una cámara totalmente hermética., The design of a loudspeaker for the marine environment involves facing various challenges in comparison with its employment in the air. The main difference lies in the high acoustic impedance of the water, which results in a considerably higher load on the diaphragm and, therefore, in the application of substantial stresses on it, and the extreme variation of static pressure to which underwater projectors are subjected. For this, a diaphragm of exceptional rigidity and very low mass is required. Likewise, a very powerful magnetic motor is required to increase the efficiency and achieve a high sound pressure level. In addition, an effective isolation between the front wave and the back wave must be ensured, by incorporating a completely hermetic chamber.

El estudio del comportamiento de los peces resulta extremadamente complicado en un entorno de libertad, especialmente si hablamos de su exposición a diferentes fuentes sonoras. Por este motivo, de las investigaciones en marcha son llevadas a cabo en el seno de un laboratorio, bien en peceras o bien en tanques, teniendo así un entorno controlado donde monitorizar continuamente el comportamiento de las muestras. Sin embargo, un recinto confinado difiere considerablemente de un espacio abierto. Mientras que un pez en libertad estará sometido por norma general a un campo sonoro libre, cuando hablamos de un recinto cerrado las condiciones cambian notablemente., Studying the behaviour of fish is extremely difficult in a free environment, especially when it comes to their exposure to different sound sources. For this reason, existing research is carried out in a laboratory, either in fish tanks or in tanks, thus having a controlled environment in which the behaviour of the samples can be continuously monitored. However, a confined enclosure differs considerably from an open space. While a fish in the wild will generally be subjected to a free sound field, when we talk about an enclosed area the conditions change markedly.

The latest studies on failures in steel truss-type bridge found that they are highly vulnerable to damage and thus prone to potential local or total collapse. Many authors recommend monitoring the critical elements in the existing steel truss-type bridges in real time to anticipate any failures in local members. Although mechanical strain is the most frequently used variable for this purpose, this method also happens to be the most expensive monitoring strategy. This paper describes a case study of failure scenarios assessment in a steel truss-type railway bridge after extensive long-term monitoring conducted by the authors, based on measuring vertical deflections and modal frequencies. The structure has both an isostatic and a hyperstatic configuration, and was assessed by means of a combination of: (i) long-term monitoring results, and (ii) a finite element analysis to simulate several failure scenarios. A sensitivity study of the different failure scenarios has been carried out, identifying those that can be detected. The results are used to define practical recommendations for failure detection by measuring vertical deflections and modal frequencies.

Vehicular traffic represents the most influential loads on the structural integrity of railway bridges, therefore the design on dynamic criteria. This work explores the use of strain dynamic measurements to characterize the health condition of railway bridges under moving train loads. Specifically, the approach proposed in this work exploits the implementation of auto-regressive (AR) time series analysis for continuous damage detection. In this light, continuously extracted AR coefficients are used as damage-sensitive features. To automate the definition of the order of the AR model, the methodology implements a model selection approach based on the Bayesian information criterion (BIC), Akaike Information Criterion (AIC) and Mean Squared Error (MSE). In this exploratory investigation, the suitability and effectiveness of strain measurements against acceleration-based systems are appraised through a case study of a simply supported Euler-Bernoulli beam under moving loads. The moving loads problem in terms of vertical accelerations and normal strains is solved through modal decomposition in closed form. The presented numerical results and discussion evidence the effectiveness of the proposed approach, laying the basis for its implementation to real-world instrumented bridges.

This work presents results allowing an unequivocal correlation of the observations of strong nonlinear elastic features of ultrasonic waves (values of the nonlinearity parameters exceeding the thresholds corresponding to undamaged states), with the critical events of the corrosion-induced surface cracking of reinforced cement-mortar specimens. These observations point to the possibility of the early detection of cracking using nonlinear ultrasonic (NLU) techniques. Experimental evidence is presented on the existence of active net mass transport processes, due to wick action, in the course of the corrosion tests, in the experimental conditions of this work. These phenomena might explain the observed abrupt shifting of the nonlinear parameter values (typically increasing and then decreasing post-peak, even reaching values typical of the undamaged state), and, partially, the high variability obtained for the values of the nonlinear parameters in damaged (cracked) states. Finally, some consequences are derived from the point of view of use of the NLU techniques in engineering practice, i.e., in surveys aimed at evaluating reinforced concrete structures affected by corrosion.

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, sensor transducer…). The main purpose of this work is to propose an alternative approach that uses a single electrodynamic actuator both as an impulse exciter and vibration sensor simultaneously. By generating a random signal excitation and measuring the electrical input impedance of the actuator when coupled to a beam-type cylindrical element, the fundamental flexural mode of vibration of the latter can be identified and the dynamic elastic modulus of its material determined in a simple and straightforward manner. Preliminary experiments were performed over different size beams with rectangular cross-sections made of natural stone, marble, wood, and aluminium. Results were compared to those obtained using the standardized procedure described in the ASTM E1876 for the same specimens, these showing a good agreement in terms of dynamic elastic modulus.

Las asignaturas incluidas en el currículum de los grados de Ingeniería se han abordado tradicionalmente desde una perspectiva conductista, empleando para ello una metodología de aprendizaje por enseñanza directa. El docente se erige como agente principal en la transmisión de conocimientos, siendo el alumno quien los ejercita a partir de la resolución de problemas y el desarrollo de prácticas de laboratorio, por norma general conducidas. Esta metodología limita de manera notable el desarrollo de ciertas capacidades por parte del alumno, por lo que resulta necesario adoptar estrategias en las que el alumno adquiera un rol más participativo y se convierta en agente principal dentro del proceso enseñanza-aprendizaje. La formación del alumnado debe abordarse como un proceso en el que entender y memorizar, pero, además, desarrollar capacidades de interrelación, cooperación, buscar información, discutir estrategias, cuestionarse los contenidos, o aplicar conceptos y metodologías. En definitiva, adquirir un papel activo y ser partícipe de su propia formación. La experiencia docente propuesta consiste en la adaptación de diferentes contenidos prácticos de la asignatura Vibroacústica, optativa de tercer curso del grado en Ingeniería en Sonido e Imagen en Telecomunicación de la Universidad de Alicante, para la aplicación de una metodología de aprendizaje basado en proyectos (ABP). Se trata de fomentar las capacidades transversales fundamentales para el desarrollo profesional del alumnado: aprendizaje autónomo, capacidad crítica, emprendimiento y colaboración. Los contenidos prácticos de la materia se encuentran divididos en cuatro bloques. El primero de ellos, permite dar a conocer las herramientas de medida y análisis disponibles en el laboratorio. El segundo se destina al análisis de vibraciones, y el tercero, a radiación. Finalmente, el último bloque se centra en la transmisión de ondas. La metodología ABP se aplicó en los bloques 2 y 4. En ambos casos, la primera sesión se

Las Tecnologías del Aprendizaje Cooperativo (TAC) constituyen sin duda una plataforma de gran interés para el profesorado y alumnado en el ámbito de la educación superior por las ventajas que ofrecen en términos de interacción y trabajo en equipo. En este estudio se recogen los resultados preliminares correspondientes a una experiencia educativa cuyo objetivo ha sido evaluar el impacto de implementar una metodología de aprendizaje cooperativo basado en la técnica del puzle de Aronson en la asignatura de últimos cursos Ultrasonidos y Aplicaciones del Grado en Ingeniería en Sonido e Imagen en Telecomunicación (GISIT) que se imparte en la Universidad de Alicante (UA). La experiencia docente ha demostrado que el uso de las TAC no solo incrementa el grado de implicación del alumnado en la resolución de una tarea común, sino que potencia sus habilidades de trabajo en equipo garantizando a su vez el rendimiento académico de las metodologías convencionales.

Durante muchos años, en las asignaturas del área de Ingeniería, el docente ha actuado como transmisor único de conocimientos, dejando al alumno en una posición secundaria en la que únicamente aplicaba lo aprendido en actividades teórico-prácticas de carácter conducido. Las limitaciones que supone esta metodología para el desarrollo de las capacidades del estudiante ha hecho necesario establecer nuevas estrategias de enseñanza-aprendizaje que garanticen una mayor implicación y motivación. El aprendizaje basado en proyectos permite abordar los contenidos desde una perspectiva más práctica y enfocada hacia entorno laboral. En la asignatura Vibroacústica, optativa de tercer curso del grado en Ingeniería en Sonido e Imagen en Telecomunicación de la Universidad de Alicante, los contenidos prácticos resultan de vital importancia. La experiencia llevada a cabo consistió en adaptar parte de dichos contenidos a una metodología de aprendizaje basado en proyectos. La actividad se analizó de forma cualitativa-cuantitativa, utilizando como instrumentos de evaluación tanto los informes presentados a la finalización de cada proyecto como un cuestionario de valoración del alumno respecto a la experiencia. Los resultados ponen de manifiesto las bondades de este tipo de metodologías en el desarrollo de actividades prácticas de laboratorio en el ámbito de la ingeniería.

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 introduces underwater acoustic energy, as detailed in Descriptor 11, and stipulates that the member states should set the threshold levels at which a good environmental status can be achieved by means of long-term monitoring campaigns. This research presents the results of a long-term underwater noise monitoring campaign with a duration of three years in the port of Cartagena located on the south-eastern coast of Spain, focusing on the monthly and annual variation patterns of low-frequency continuous noise. The acquired data are classified according to the source of the acoustic noise into shipping, other anthropogenic, and natural noise measurements. These three groups of measurements are processed in order to obtain one-third octave band levels centered at 63 and 125 Hz, as well as the overall bandwidth of unweighted Sound Pressure Level (SPL). The analysis of the measurements shows an increase in the annual average overall band of 4 and 3 dB of the natural and shipping noise, respectively, from 2013 to 2015. This monitoring campaign provides accurate acoustic values to establish threshold levels to achieve good environmental status and recommendations to conduct monitoring programs and regulations to control underwater noise pollution.

[EN] Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still exists, and results are often tentative or qualitative. A monitoring methodology for the behavioral response of bluefin tuna (Thunnus thynnus) when exposed to ship and wind turbine operational noises was implemented and tested in a fixed commercial tuna feeding cage in the Mediterranean sea. Fish behavior was continuously monitored, combining synchronized echosounder and video recording systems. Automatic information extracted from acoustical echograms was used to describe tuna reaction to noise in terms of average depth and vertical dimensions of the school and the indicators of swimming speed and tilt direction. Video recordings allowed us to detect changes in swimming patterns. Different kinds of stimuli were considered during bluefin tuna cage monitoring, such as noise generated by feeding boats, wind farm operational noise, and other synthetic signals projected in the medium using a broadband underwater projector. The monitoring system design was revealed as a successful methodological approach to record and quantify reactions to noise. The obtained results suggested that the observed reactions presented a strong relationship with insonification pressure level and time. Behavioral changes associated with noise are difficult to observe, especially in semi-free conditions; thus, the presented approach offered the opportunity to link anthropogenic activity with possible effects on a given marine species, suggesting the possibility of achieving a more realistic framework to assess the impacts of underwater noise on marine animals.

Los estudios realizados sobre ruedas suelen tener en cuenta muestras de grandes dimensiones: ruedas de coches (neumáticas) o trenes (no neumáticas). No obstante, con relación a estructuras más reducidas no existen demasiados estudios. En el presente trabajo se propone una metodología experimental no destructiva y de bajo presupuesto para la caracterización de ruedas no neumáticas empleadas habitualmente en patines y patinetes. Estos elementos son de tamaño reducido y por norma general se encuentran compuestos por elastómeros como el poliuretano, lo que les confiere un comportamiento hiperelástico. Mediante el uso de instrumental de reducido tamaño, diseñado y fabricado a medida, se logra excitar la estructura de forma impulsiva. A partir de la respuesta del sistema, obtenida a partir de un micrófono de medida, se realiza un análisis modal operacional de la estructura. La repetición sistemática de medidas en campo cercano, en un plano paralelo a la superficie de la muestra, permite la identificación de las formas modales del sistema sin afectar al comportamiento del mismo. A partir de los resultados, se lleva a cabo el ajuste de un modelo numérico en FEM con el fin de establecer las propiedades mecánicas aparentes de cada uno de los componentes principales de la rueda., The studies about wheels only take in account the samples of big size: car (pneumatic - wheel) or train (non - pneumatic - wheel). However, there is a lack of effort about small structure in this field. In this work is proposed an experimental, low-cost methodology for the characterization of non-pneumatical wheels of small size, typical of roller-skates. Which are usually composed by hyperelastic polymers as PU (Polyurethane). By using a set of small-size 3D printed tools it could be done an impulsive excitation over the structure for an OMA (Operational Modal Analysis) study of the structure. The systematic near-filed measurements in a plane parallel to the wheel can be used to reconstruct and identify the different vibration modes of the structure. Finally, the results have been used to fit a numerical method has been in FEM, with the aim of obtain the apparent physical properties of the different elements of the wheel.

El uso de la mascarilla resulta un elemento indispensable a la hora de limitar la propagación del COVID-19, siendo obligatoria en cualquier espacio público, incluidas las aulas de enseñanza. Por la posición que ocupa, este equipo de protección individual puede influir de manera notable en el mensaje hablado y, por tanto, en la comprensión oral por parte del receptor. El objetivo de esta investigación se centra en el estudio de la influencia de la mascarilla en la comprensión auditiva del alumnado y sus posibles efectos sobre el aprendizaje. El estudio se divide en cuatro bloques fundamentales. En primer lugar, se analizan los efectos de las mascarillas de uso más habitual (quirúrgica y FFP2) en el nivel de presión sonora emitido por el orador. Seguidamente, se determina su influencia sobre el mensaje hablado por medio de un análisis espectral. En tercer lugar, a partir de ensayos de audiometría verbal, se establece el nivel de inteligibilidad del oyente para cada muestra empleada. Para finalizar, con el objetivo de valorar tanto el grado de influencia de la mascarilla en la actividad docente como en el aprendizaje del alumno, se llevan a cabo encuestas en diferentes ámbitos de la comunidad educativa: secundaria, bachillerato y universidad. Los resultados muestran una influencia significativa de la mascarilla en el habla desde el punto de vista físico y perceptual.

La situación de pandemia actual ha supuesto un nuevo paradigma en la educación universitaria. La reorganización de espacios necesaria para garantizar las medidas de salubridad ha obligado en muchos casos a establecer una nueva metodología docente, especialmente en el entorno de prácticas de laboratorio, donde la manipulación de equipos se ha visto considerablemente reducida. En este sentido, el uso de entornos de trabajo virtuales puede ayudar a suplir las carencias actuales. Esta investigación surge como iniciativa para una posible contribución a la mejora de la actividad docente y su objetivo se centra en valorar el uso de herramientas virtuales para la realización de prácticas de laboratorio en el campo de la física. El estudio, de tipo cuantitativo y cualitativo, se llevó a cabo por medio de encuestas en las que participaron un total de 122 alumnos. Los resultados obtenidos muestran una clara preferencia del estudiante en favor de actividades de carácter manipulativo. Sin embargo, también ponen de manifiesto las bondades de este tipo de herramientas en el desarrollo formativo del alumno. La utilización de entornos virtuales puede suponer, por tanto, un instrumento de apoyo adicional en el proceso formativo, otorgando mayor versatilidad e independencia al estudiante.

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 to several situations, is selected. One way of providing a more appropriate acoustic performance for each function of the auditorium is using variable sound absorption techniques to control reverberation and other relevant acoustic phenomena associated to sound perception. In this paper, the acoustic behavior of a perforated system that may be suitable for achieving a variable acoustic solution for room acoustic design is addressed. In the design of a cost-effective solution, the surface appearance is kept unchanged, while variable acoustic behavior is achieved either by closing the holes in the back face of the perforated panel or by placing a porous material in varying positions inside the backing cavity, thus accomplishing different acoustic requirements within a multipurpose auditorium. An analytical approach, based on the transfer matrix method is employed for preliminary acoustic sound absorption assessment provided by the system and to develop optimized solutions. Diffuse sound absorption is then computed and used to simulate, by the ray-tracing method, the acoustic behavior of a multipurpose auditorium to demonstrate efficient acoustic performance for different types of use.

Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still exists, and results are often tentative or qualitative. A monitoring methodology for the behavioral response of bluefin tuna (Thunnus thynnus) when exposed to ship and wind turbine operational noises was implemented and tested in a fixed commercial tuna feeding cage in the Mediterranean sea. Fish behavior was continuously monitored, combining synchronized echosounder and video recording systems. Automatic information extracted from acoustical echograms was used to describe tuna reaction to noise in terms of average depth and vertical dimensions of the school and the indicators of swimming speed and tilt direction. Video recordings allowed us to detect changes in swimming patterns. Different kinds of stimuli were considered during bluefin tuna cage monitoring, such as noise generated by feeding boats, wind farm operational noise, and other synthetic signals projected in the medium using a broadband underwater projector. The monitoring system design was revealed as a successful methodological approach to record and quantify reactions to noise. The obtained results suggested that the observed reactions presented a strong relationship with insonification pressure level and time. Behavioral changes associated with noise are difficult to observe, especially in semi-free conditions; thus, the presented approach offered the opportunity to link anthropogenic activity with possible effects on a given marine species, suggesting the possibility of achieving a more realistic framework to assess the impacts of underwater noise on marine animals.

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.

Many industrial and consumer applications require their components be activated to achieve the desired functionality. In most of the cases, the activation is produced by gear-motors, which adapt speed and torque to the specifications set forth in the design process stage. On the whole, gear-motors consist of a motor as the main energy source provider and a kinematic chain to transmit and transform the energy into a mechanical force - a torque - usually in the form of a thrust. The motor is also one of the most important noise sources in gear-motors; consequently, its choice largely determines its acoustic behaviour. In this paper, a study of the sound features of small electric motors is carried out with the aim of determining a metric that help select the most suitable motor for small electromechanical devices. A semantic differential method has been adopted to evaluate the users’ perception of attributes such as annoyance, power, robustness, condition, acoustic behaviour, quality, and price.

Underwater noise has been identified as a relevant pollution affecting marine ecosystems in different ways. Despite the numerous studies performed over the last few decades regarding the adverse effect of underwater noise on marine life, a lack of knowledge and methodological procedures still exists, and results are often tentative or qualitative. A monitoring methodology for the behavioral response of bluefin tuna (Thunnus thynnus) when exposed to ship and wind turbine operational noises was implemented and tested in a fixed commercial tuna feeding cage in the Mediterranean sea. Fish behavior was continuously monitored, combining synchronized echosounder and video recording systems. Automatic information extracted from acoustical echograms was used to describe tuna reaction to noise in terms of average depth and vertical dimensions of the school and the indicators of swimming speed and tilt direction. Video recordings allowed us to detect changes in swimming patterns. Different kinds of stimuli were considered during bluefin tuna cage monitoring, such as noise generated by feeding boats, wind farm operational noise, and other synthetic signals projected in the medium using a broadband underwater projector. The monitoring system design was revealed as a successful methodological approach to record and quantify reactions to noise. The obtained results suggested that the observed reactions presented a strong relationship with insonification pressure level and time. Behavioral changes associated with noise are difficult to observe, especially in semi-free conditions; thus, the presented approach offered the opportunity to link anthropogenic activity with possible effects on a given marine species, suggesting the possibility of achieving a more realistic framework to assess the impacts of underwater noise on marine animals.

One of the most aggressive attacks to which cement-based materials can be exposed is that produced by sulphate. During this attack, expansive products are formed, causing volumetric strains in hardened materials, which brings microcracking and the reduction of their strength and durability. The use of non-destructive techniques for characterizing the microstructure of cement-based materials, and for following the development of deleterious processes which can affect them, has become an important research field. Among them, non-linear ultrasonic (NLU) techniques have shown to be useful for evaluating the material degradation. The aim of this work is to study the possibility of using the NLU technique for the non-destructive evaluation of initial development of internal sulphate attack in cement-based materials. Cement pastes were prepared using ordinary Portland cement, to which an appropriate amount of calcium sulphate 2-hydrate was added during the setting for producing an internal attack in the samples. Furthermore, its effects in the microstructure have been followed with mercury intrusion porosimetry. The expansion and linear ultrasonic pulse velocity were also determined. The preliminary results indicate that the NLU technique could be useful for studying the development of sulphate attacks in the short-term, complementing the information provided by other techniques.

La red de investigación en docencia universitaria cuyos resultados se resumen brevemente en la presente memoria propone una plataforma software para la caracterización de materiales acústicos que sirva de complemento a la plataforma experimental desarrollada en el mismo contexto durante el curso pasado. En concreto, se pretende dotar tanto al alumnado como al profesorado implicado en la docencia de las asignaturas del IIA (Itinerario de Ingeniería Acústica) del GISIT (Grado en Ingeniería en Sonido e Imagen en Telecomunicación) de una herramienta que facilite el aprendizaje de los procedimientos nacionales e internacionales de caracterización de materiales acústicos desde un entorno virtual. Además, al valerse de un entorno de programación ampliamente utilizado durante la carrera, dicha herramienta no solo permite al alumnado implicarse en el desarrollo de la misma, sino que también ofrece interesantes posibilidades de escalabilidad en el futuro gracias a su estructura modular.

El desarrollo de nuevas herramientas y recursos que faciliten y garanticen una formación de calidad constituye una de las principales líneas de trabajo en la investigación en docencia universitaria. Entre los recursos tecnológicos existentes, las plataformas softwares quizás sean unas de las elecciones más comunes por parte del profesorado gracias a su fácil escalabilidad y versatilidad de uso. Este trabajo presenta los resultados preliminares correspondientes del desarrollo de una plataforma software para el Itinerario de Ingeniería Acústica del Grado en Ingeniería en Sonido e Imagen en Telecomunicación. En concreto, la plataforma implementada permite servir como vehículo de aprendizaje de los métodos de caracterización de materiales acústicos, así como de los fundamentos teóricos subyacentes, en las asignaturas que conforman dicho itinerario. A partir de esta herramienta, el alumnado será capaz no solo de conocer en detalle los procedimientos normativos nacionales e internacionales utilizados habitualmente para dicho fin, sino también reforzar los conceptos teóricos asociados a los mismos desde un entorno virtual que complemente al de un laboratorio de medida.

Uno de los factores de éxito más importantes en el ámbito educativo corresponde a la motivación del alumno. Por tanto, resulta de vital importancia conocer sus expectativas y tenerlas en cuenta a la hora de establecer una planificación docente apropiada. El grado en Ingeniería en Sonido e Imagen en Telecomunicación en la Universidad de Alicante, cuenta con un itinerario formativo en el área de Ingeniería Acústica. Esta investigación surge como iniciativa para la mejora de la actividad docente en dicho itinerario y sus objetivos se centran en conocer las expectativas del alumnado en relación a diferentes aspectos del mismo. El estudio, de tipo cuantitativo, se llevó a cabo por medio de encuestas en las que participaron un total de 69 alumnos. Los resultados ponen de manifiesto un gran desconocimiento de las materias impartidas en el itinerario, así como de las salidas profesionales asociadas a la Ingeniería Acústica. De acuerdo con las preferencias del alumnado, resulta primordial orientar los programas docentes a las demandas del mercado laboral. Asimismo, los contenidos prácticos y la incorporación en el proceso formativo de charlas o debates realizados por expertos del sector pueden ayudar en gran medida a lo largo del proceso de aprendizaje.

The aim of this work was to provide further confirmation of the possible use of non-linear ultrasonic techniques for detecting the cracking due to corrosion of steel reinforcements in concrete. To this end accelerated steel corrosion tests have been conducted on model reinforced cement mortar specimens, while monitoring the appearance and width evolution of visible surface cracks, and performing non-linear ultrasonic measurements based on the phenomena of harmonic distortion and intermodulation. A new parameter, based on the difference between the amplitude of the fundamental frequency and the sum of the amplitudes of all the first-order and second-order intermodulation products, has been proposed in this work. The results confirm that the appearance of visible surface micro-cracks are preceded and accompanied by the observation of strong non-linear features in the received signal. Furthermore, the new parameter proposed in this work is as efficient as the relative non-linearity parameters, classically used in harmonic distortion non-linear ultrasonic studies, for detecting the non-linear features associated with the critical events of the cracking of cement mortar due to embedded steel corrosion. A hypothesis has been developed considering the possible effect of the filling of the void space by liquid containing rust products after the formation of new cracks or the enlargement of its width. This filling process, which might be particularly enhanced by net convective transport of liquid, would explain the evolution of the values of all the parameters used for putting in evidence the non-linear elastic features after the critical events of the cracking process.