Davide Borelli

Normative framework for ship noise: Present and situation and future trends

The paper addresses the present regulatory framework regarding ship noise emissions both towards the internal spaces onboard and the external environment (in air and in water). A different level of development has been reached in the various areas for the definition of the needs for the noise control and for their implementation in a normative framework. This is due in part to the different point in time in which the different aspects were recognised to be relevant and therefore studied, assessed and regulated. The analysis of existing regulations is the basis for considering the present situation, on-going developments and possible future trends as regards the evaluation of ship noise impact on the various types of environment. The situation of the requirements developed for the maritime field appears to be in line with other fields of engineering as regards the definition of noise limits for the working environment, while the definition of comfort of living on board seems to be somehow lacking behind other fields, with possibility of taking advantage of their experience. Well established assessment procedures for external radiation in air appear to be not yet available and in this case a need for specific developments arises. Finally, for underwater noise emissions, there is availability of relatively well developed requirements, that however are not adequately correlated to the quantification of the effects of the noise emissions on the marine fauna.

A finite element model to predict sound attenuation in lined and parallel-baffle rectangular ducts

The present article describes a Finite Element Model (FEM) model for the analysis of sound attenuation in lined and parallel-baffle rectangular ducts. By means of the numerical model it was possible to predict insertion losses in a frequency range up to 8000 Hz. The model was validated by comparing numerical results with experimental data obtained in accordance to EN ISO 11691 and EN ISO 7235 standards. For the lined ducts both lining thickness and physical properties of lining were varied during validation; the comparison indicates a good accuracy of the numerical model for all different tested conditions. The results of the validation for parallel-baffle rectangular ducts show that also the behaviour of these dissipative/reactive silencers, with their internal-reflections and energy dissipation phenomena, can be predicted quite well by the FEM model on the whole frequency range. Overall comparisons suggest that FEM modelling can be an accurate and inexpensive way to predict sound attenuation in lined ducts and parallel-baffle mufflers.

Experimental study on sound absorbing performance of rubber crumb

The present paper describes an experimental campaign aimed at the determination of acoustical properties of vulcanized rubber crumbs obtained by the shredding of used tires. In particular, their performance as sound absorbing material in lined ducts has been investigated. The most innovative aspect that is addressed in the study is the use of a waste material such as rubber tires reduced into small grains as a sound absorbing material: tires are in fact usually used at the end of their life cycle as fuel and burned in cement kilns in order to take advantage of their high heating value, with all the problems of pollution that this solution produces. Two kinds of rubber crumbs have been investigated in terms of characteristic dimension of the grains, porosity, and sound absorbing coefficient, while their “in situ” performance when used inside lined and parallel-baffle rectangular ducts has been evaluated measuring their insertion loss. The results of this research show that the acoustical behavior of the te...

Holistic control of ship noise emissions

Abstract The sustainability of anthropogenic activities at sea is recently gaining more and more attention. As regards shipping, emissions from ships into the environment of various nature (engine exhaust gases, anti-fouling paints leaching, ballast exchange, releases at sea of oil and other noxious liquid or solid cargoes, of sewage and of garbage) have been recognized as sources of pollution and therefore controlled and limited since a long time. The subject of noise emission has been identified only recently. To study the problem, the EU has funded, among others, the FP7 SILENV (Ship Innovative soLutions to rEduce Noise and Vibrations) project that run from 2010 to 2012. In the present work, the holistic approach followed within the project to characterize and control the ship as a source of noise is presented. Three types of noise emissions (in air, in water and inside the ship) are analyzed highlighting peculiarities and different strategies adopted to characterize the source, the impact on the receiver and the possible solutions to set limits to the ship emissions. The project outcome included a socalled “Green Label”: a set of new prenormative requirements defined for the three main areas mentioned above.

The impact of environmental noise generated from ports: outcome of MESP project

Abstract Ports are characterized by several complex operations. Accordingly, the analysis of noise results is complicated due to the presence in the same area of diverse sound from ships, trade and also from industrial and shipyards activities aswell as auxiliary services producing negative effects on natural ecosystem and the urban population. The ENPI CBC MED project Managing the Environmental Sustainability of Ports for a durable development (MESP) addressed the pollution reduction from port activities through the implementation of a multidisciplinary approach in air, noise andwater sectors, encompassing technological, regulatory and administrative solutions to ensure natural and urban sustainability and high level of life quality in surrounding territories. To prevent a heterogeneous development, the “status quo” of ports in Northern and Southern Shores of the Mediterranean Sea was analyzed and a guideline on methodologies, good practices and measurement assessment, adaptable and transferable in different port contexts was elaborated. To assess the procedures, validation tests have been carried out to different real cases. In noise sector pilot projects in the ports of Patras, Greece, and Tripoli, Lebanon, have been implemented. Due to the dissimilar scenarios, in terms of orography, facilities and activities, different noise mitigation actions and interventions were consequently accomplished.

Acoustical study of historical large room for a contemporary use: The oratory of Albergo dei Poveri in Genova

The conversion of deconsecrated religious buildings in conference halls or music auditoria is nowadays frequent, especially throughout Italy and Europe, although in most cases these rooms are under artistic and architectural preservation due to their historical heritage value. In this way, acoustic control interventions in such spaces, generally characterized by high reverberation time values, tend to be highly complex. The Oratory of “Albergo dei Poveri” building in Genova, transformed during the 90s in the Auditorium of the Departments of Law and Political Sciences of the University of Genova, faced these needs. After several interventions regarding the installation of sound systems and acoustical curtains, nowadays the acoustical features of the room are not still sufficient for the achievement of the adequate acoustic comfort. In this paper, the acoustic analysis of the hall has been evaluated and effective correction interventions at the same time compliant and non-invasive with the architectural con...

Noise Mapping of the Flyover Highway in Genoa:comparison of different methods

Abstract In urban noise mapping the accuracy of the simulation tools is often challenged by the complexity of the modeled scenario, particularly when its extent coincide with the whole city. In this paper, a meaningful case study is reported concerning the flyover highway “Aldo Moro” in Genoa. The particular morphology of the city and the location of the highway make it a significant test for analyzing the effectiveness of current modeling tools in simulating complex urban areas. Noise mapping has been implemented in accordance with the standardNMPB-Routes- 2008. Results have been then analyzed complying with the END. Next diverse computational methods have been compared, considering ISO 9613-2, NMPB-Routes-1996, and Harmonoise, and even different frequency partitions (octave band or one-third octave band) for the last two standards. The computational time for the different calculation methods has been analyzed. In order to get a reciprocal validation, the simulated noise maps have been finally compared with maps coming from on field measurements. In this way a case study helpful for public administrations and stakeholders facing similar issues is provided, defining the state of the art and the forthcoming perspectives.

Analysis of sound absorption behavior of polyester fiber material faced with microperforated panels

Perforated facings used in lined ducts or sound absorbing panels can have various purposes: protecting the porous sound absorbing material from dust or grazing flow, acting as a rigid support for the porous material, or also affecting the behavior of the “backing” material, modifying this way the acoustical performance of the porous layer. This paper describes the effect of perforated facings on sound absorption characteristics of samples made by polyester fiber, experimentally investigated in accordance with ASTM C384 04 standard by means of two Kundt’s tubes with different diameters. The polyester (PET) fiber material had bulk density of 30 kg/m3 and melting point at 260°C. The analysis was performed for a sample thickness equal to 100 mm. The samples were faced by means of different metal plates perforated with circular holes. The holes diameter was equal to 2 mm for all facings, while the percent open area was varied from 4.9% to 30%. The microperforated panels (MPPs) were positioned in adherence of t...

Theoretical and numerical modelling of a parallel-baffle rectangular duct

The paper describes the theoretical and numerical analysis of sound attenuation in a parallel-baffle rectangular duct. Insertion losses in a frequency range up to 8000 Hz were predicted by means of a FEM numerical model and by means of analytical models from Sabine and Kurze. The models were then validated in the frequency range from 125 to 8000 Hz by comparing theoretical and numerical results with experimental data obtained in accordance to EN ISO 11691 and EN ISO 7235 standards. The results of the comparison indicate that the behavior of such a dissipative/reactive silencer, with its internal-reflections and energy dissipation phenomena, can be predicted quite well by the FEM model on the whole frequency range. On the contrary, analytical models show little accuracy and such predictions are not always so accurate as design requires; besides, the complexity of the analytical approach tends to limit its application to the common design practice. Overall comparisons suggest that FEM modeling can be an acc...