Development of a window system with optimised ventilation and noise-reduction performance: an approach using metamaterials.

Noise transmission is a key factor regarding indoor comfort and energy-smart Architecture and Engineering. In most cases, occupants of the building must choose between a naturally ventilated indoor environment or a quiet one. On the other hand, the acoustic metamaterials (AMMs) allow more customisable physical properties according to their spatial configurations, proving significant merits over traditional architecture and engineering materials. This PhD study will investigate AMMs techniques to develop a window system that can control the incoming noise while allowing natural ventilation. This is a crucial point for AMMs research. So far, even if many solutions have been developed to pursue this objective, they still lack ergonomics and human perception analysis. Through a multi-disciplinary methodology, the author first a) highlighted which are the ergonomic principles that add value to the window system from the users perspective, then b) investigated a series of suitable AMMs techniques to be applied for noise reduction and natural ventilation, c) developed a specific AMM design suitable to follow those ergonomic principles previously highlighted and assessed it through human perception, and finally d) optimised a full-scale prototype for a broad acoustic range and customisable ergonomic application. Social science, ergonomic, numerical, analytical and experimental studies were used throughout the PhD project to draw a full-scale window prototype using AMMs to allow natural ventilation independently from the outdoor noise situation. The so-called acoustic metawindow (AMW) allows Transmission Loss (TL) of 10-80dB on a significant frequency range for human hearing (50-5000Hz) in an open configuration while allowing sufficient natural ventilation. In addition, the AMW is proved to positively impact the indoor environment from both physical and human perception points of view thanks to its ergonomic nature. This project will open a new AMMs field of investigation that is not limited to noise reduction but also includes outdoor stimuli optimisation towards a more comprehensive indoor comfort

Development of a window system with acoustic metamaterial for air and noise control

To improve window performances in reducing noise and allowing for air exchange, most current approaches focus on techniques such as double glazed and ducted designs, generally leading to bulky designs, visually non-optimised, and with narrow-banded frequency. In this research, window systems based on acoustic metamaterials (AMMs) are developed, and both natural air ventilation and acoustic performances are evaluated. The systems incorporate bistable auxetic metamaterials and acoustic origami metacage designs which are particularly interesting for their reconfigurable and deployable nature. Several design cases with different design features are examined, and a specific design is then selected for a parametric analysis using Finite Element Method (FEM) aiming to optimise the acoustical performance. It is demonstrated that significant improvement in acoustic performance can be obtained in terms of Transmission Loss (TL). The use of AMMs could lead to designs with manifold merits over traditional windows, including compact size with deployability, easy reconfigurability and installation, and thus paving new direction in ventilation window design

Design of urban furniture to enhance the soundscape: A case study

In modern urban scenarios all the aspects of the historical heritage, including public open spaces and ancient buildings, have to meet the high increase of density of infrastructures and constructions, with the consequent change of visual and sound environments. This in turn affects people’s quality of life. Because of the growing interest on this problem, this study investigates the relationship between soundscape and design solutions for urban furniture, considering technical and environmental feasibility of the designing process, from the materials characteristics, to the acoustic and psychoacoustic impact of the tool on the user. The process includes the acoustic suitability of 3D printing materials, the suitability of acoustic design using software simulation, the experimental assessment of the performance of the 3D printed prototype, and the statistical evaluation of the chosen studying parameters and conditions. This paper describes all the stages of the designing process, with a focus on the study of shapes and volumes of the prototype and on its impact on the user’s perception. FEM simulations and experimental tests performed in a semi-anechoic chamber allowed to validate the design process. These analyses proved that the designed prototype of urban furniture can not only positively influence the physical environment but also the psychoacoustic perception of it

Acoustic Requalification of an Urban Evolving Site and Design of a Noise Barrier: A Case Study at the Bologna Engineering School

The increase in new infrastructure development has raised closer attention to the environmental noise of new expansion areas. This study investigates the urban evolution of Terracini Street’s surrounding area in the Navile district, Bologna, Italy. In the last 20 years, this area has undergone various transformations, from a suburban industrial area to a new university and residential one. First, the morphologic and infrastructural characteristics of the site are established. Then, the existing regulations (acoustic, urban, and infrastructural regulations, whether local or national) are evaluated. Next, the results of environmental noise measurements are presented. Since a heavily trafficked infrastructure is very close to the occupied public area, noise limits are severely exceeded. A noise mitigation design stage follows, focusing on a novel noise barrier design. Specifically, particular attention is paid to the visual and ecological impact of the noise barrier on the area’s landscape, which must be representative of the new location of the School of Engineering. The sonic crystal technique is exploited to implement an effective noise barrier (average insertion loss of 10 dB(A) in the 200 Hz–1 kHz range), allowing air ventilation and visual transparency. This case study could further evolve using other acoustic metamaterial techniques or in different application sites

The influence of thermo-hygrometric conditions on metamaterials' acoustic performance: an investigation on a 3-D printed coiled-up resonator

In the last decades, coiled-up resonators have become popular within the metamaterial research community for narrow band, low frequency resonances combined to sub-wavelength thickness. Such structures are particularly suited to one of the most widespread manufacturing processes, i.e. PET-based 3D printing. Acoustic performance of coiled-up resonators depends on the geometrical parameters’ variation, which is influenced by thermo-hygrometric conditions; however,the deformation itself needs to be further investigated. For this reason, the present paper evaluates the correlation between temperature, relative humidity, and the geometrical parameters’ (spiral length and hole diameter) deformations and, consequently, the acoustic performance of a 3D printed coiled-up resonator. A combined approach through analytical, numerical, and experimental measurements quantified the coefficient increasing the temperature (T = 10 – 50 °C) , and the relative humidity (RH = 20 – 50 – 80 %) of the samples. Relative humidity variations turned neglectable discrepancies on sound absorption’s peaks. On the other hand, the increase in temperature caused a frequency peaks’ shift following an exponential trend. This study can be a starting point for practical applications when the thermos-hygrometric variations are of concern

MPP sound absorbers investigation to optimize a lecture hall speech intelligibility

The recent pandemic has drawn attention to the built environment’s hygiene, sustainability, and durability. Furthermore, studies on micro-perforated panels (MPPs) have recently highlighted their potential for sound absorption in such a context. On the other hand, metal additive manufacturing has become a very popular and convenient method to test acoustic metamaterials (AMMs) performance; however, their deployability in several civil indoor environments and functions still lacks assessment. So, the present work assesses the suitability of metal 3D printed MPP systems to fulfil speech requirements in lecture rooms. Firstly, an analytical optimization process defined two MPP steel specimens in terms of sound absorption performance. Secondly, these models were physically manufactured through 3D additive metal printing, and their acoustic performance was measured experimentally on a double-layer configuration. Finally, experimental results were used as input data for characterizing finite-difference time-domain (FDTD) simulations, highlighting the potential enhancement of oral communication through double-layer MPPs on the ceiling of a historical university lecture hall. An FDTD code with a full-spectrum wave-based method was chosen to better handle time-dependent signals, like verbal communication. The outcomes of the process show the influence of the acoustic treatment in terms of reverberation time (T30)

Rapid spread of a new West Nile virus lineage 1 associated with increased risk of neuroinvasive disease during a large outbreak in northern Italy, 2022: One Health analysis

A new strain of WNV lineage 1 (WNV - 1) emerged in the Veneto Region, northern Italy, in 2021, eight years after the last outbreak of WNV - 1 in Italy. The virus, which co-circulates with WNV-2, has become endemic in the Region, where, in 2022, most human cases of neuroinvasive disease (WNND) reported in Europe have occurred