Active control of sound radiated by vibrating surfaces on a McLaren supercar

Sound radiators based on forced vibrations of plates are becoming widely employed, mainly for active sound enhancement and noise cancelling systems, both in music and automotive environment. Active sound enhancement solutions based on electromagnetic shakers hence find increasing interest. Mostly diffused applications deal with active noise control (ANC) and active vibration control systems for improving the acoustic experience inside or outside the vehicle. This requires investigating vibrational and, consequently, vibro-acoustic characteristics of vehicles. Therefore, simulation and processing methods capable of reducing the calculation time and providing high-accuracy results, are strongly demanded. In this work, an ideal case study on rectangular plates in fully clamped conditions preceded a real case analysis on vehicle panels. The sound radiation generated by a vibrating flat or shallow surface can be calculated by means of Rayleigh’s integral. The analytical solution of the problem is here calculated implementing the equations in MATLAB. Then, the results are compared with a numerical model developed in COMSOL Multiphysics, employing Finite Element Method (FEM). A very good matching between analytical and numerical solutions is shown, thus the cross validation of the two methods is achieved. The shift to the real case study, on a McLaren super car, led to the development of a mixed analytical-numerical method. Optimum results were obtained with mini shakers excitement, showing good matching of the recorded SPL with the calculated one over all the selected frequency band. In addition, a set of directivity measurements of the hood were realized, to start studying the spatiality of sound, which is fundamental to active noise control systems

Analytical and Numerical Models of the Sound Radiated by Fully Clamped Rectangular Vibrating Plates

I n the present work, fully clamped rectangular isotropic plates are investigated: the response under steady-state excitation determined by harmonic point force application is calculated, and the consequent sound radiation is evaluated. The study is carried out both analytically and numeri cally. At first, the analytical solution of the clamped-clamped plate motion equation is calculated by means of a MATLAB implementation. The solution is based on the Principle of Virtual Work, calculating the displacement as a function of frequency at the nodes of a rectangular mesh. The monopole approximation of Rayleigh’s integral is then used to estimate the sound radiation in free field propagation. The numerical solution is evaluated using COMSOL Multiphysics, employing the Finite Elements Method (FEM). The clamped plate is modeled as a shell and “Acoustic-Structure Boundary” coupling is employed. Furthermore, the optimization of force application point is performed, with the aim of maximizing the radiated sound pressure level or flattening the frequency response. Very good matching between analytical and numerical methods has been found. In conclusion, a reliable prediction model of the sound pressure radiated by clamped plates in the low frequency range is achieved

Ragioni per il contenimento dell'uso del suolo: i costi delle urbanizzazioni a confronto

Il paper analizza le implicazioni, ambientali ed economiche, legate al consumo di suolo, o meglio all’utilizzo dei suoli prevalentemente agricoli per le urbanizzazioni. La riflessione su questo tema è all’ordine del giorno della comunità scientifica, con lo scopo di rispondere alle domande: • il continuo utilizzo di suoli, spinto dalle esigenze di bilancio dei comuni, genera risorse - tramite gli oneri di urbanizzazione - tali da giustificare parzialmente la scelta? • il bilancio complessivo, se si considerano gli impatti ambientali, non è invece negativo, tale da indurre una inversione di tendenza? • come si possono compensare le urbanizzazioni in corso di realizzazione in modo da limitare gli impatti? Il lavoro tende a dimostrare la tesi senza preconcetti e con tutte le approssimazioni introdotte dalla stima economica di beni ambientali, annosa e controversa questione. L’impatto ambientale ed il costo economico di un “abitante teorico insediato” sono valutati tramite l’Impronta Ecologica (per le componenti relative ai consumi non alimentari e non riconducibili alle abitudini dei singoli individui) e l’analisi del piano urbanistico e del bilancio comunale,. Il caso di studio è tratto da un territorio omogeneo dal punto di vista morfologico, economico e sociale quale è la Franciacorta, area ad ovest della città di Brescia, rinomata per la produzione vitivinicola di qualità. Sulla base del lavoro presentato si potrebbe puntare a raggiungere una maggiore affidabilità del dato, aumentando la quantità di casi studio per l’analisi dei costi e analogamente le componenti impattate per la mitigazione ambientale

Municipal Budget Management and the Generation of Urban Sprawl. A Case Study of the Lombardy Region (Italy)

The paper describes one of the Italian sprawl drivers: the circle triggered by the use of urban charges to solve budget problems. From 2005 to 2018, Italian municipalities could use urban charges to solve normal budget problems: they could plan new urban areas to provide new urban charges, new building and services, and they could manage old and new services at the expense of normal budget. The planning of unnecessary urban areas was effectively influenced by budget problems. The paper illustrates this issue during a period without open data sources in order to improve land management and environmental sustainability

[Applicazione di metodi di analisi speditiva per valutare le opportunità di rigenerazione urbana nei territori diffusi delle risorse tra progetti di forestazione urbana]

The success of an urban redevelopment project is often determined by the preliminary study of the site and by the knowledge thereby acquired to guide the regeneration strategies. Local administrations of small and medium-sized municipalities are unable to play a strong role in governing regeneration since Urban Plans do not include strategic analyses of the regionswide focussing on abandoned or unused areas. A clearly-oriented framework of knowledge can make it possible to regulate urban renewal more effectively and ensure a greater likelihood of successful redevelopments. The paper presents a fast method that highlights the objective limits of brownfield sites in order to better support decisions related to the Urban Plan forecasts. The method is based on four main indicators: Accessibility, Density, Functional Mix and Compactness that link a site to the context. The quali-quantitative evaluation of the indicators and their sub-components allows the establishment of the weaknesses and the strengths of the site within the urban fabric in which it is located. The method is tested by applying it to three case studies in the area of Franciacorta in the Province of Brescia

Spatial Planning Policy for Sustainability: Analysis Connecting Land Use and GHG Emission in Rural Areas

Anthropogenic greenhouse gas (GHG) emissions are the highest they have ever been and the climate change they have triggered is having consequences on both human and natural systems. The aim of the paper is to demonstrate that an integrated reading of urban and rural land uses in relation to GHG emissions is feasible and useful at the regional level in order to reach emissions reduction. The Po Valley in Italy is an emblematic case study because its features are unique in Europe for high population density, urban sprawl, intensive agriculture, livestock management and consequently high emission levels. The methodology examines the total GHG emissions in relation to urban and rural areas. Between 2000 and 2010, the trend of CO2-equivalent emissions for the macro-regions of Italy shows a national decrease in contrast to the area of our case study which has seen a steady increase and growth trend over time. The paper analyzes some possible reasons linked to this anomaly, and it presents an estimation of the CO2-equivalent emissions related to the use of agricultural land. The main output of the paper is a new overview for research that aims to propose integrated solutions and policies at the local level with a wider vision focused on GHG emission knowledge, supported by Strategic Environmental Assessment

Problematiche di analisi dell’offerta dei servizi alla persona

La XVIII Conferenza Nazionale della SIU - Società Italiana degli Urbanisti è stata pensata come un'occasione di riflessione collettiva intorno alle condizioni e prospettive del nostro Paese che, dopo le grandi trasformazioni vissute nella seconda metà del Novecento, sta ora attraversando una fase di profonda crisi che può e deve aprire verso nuove e diverse prospettive di intervento e di governo del territorio. Il titolo "Italia '45-'45. Radici, Condizioni, Prospettive" intende fare riferimento a ciò: alla necessità di riflettere con quanta più chiarezza possibile sul presente, sulle condizioni del territorio e delle città italiane sullo sfondo dei processi che le hanno determinate e al contempo guardare in avanti, in prospettiva, riconoscendo la necessità di lavorare al futuro, di immaginare scenari, costruire visioni, piani, progetti e politiche territoriali per il Paese con una prospettiva di lungo periodo