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The Underwater Radiated Noise (URN) from ships has gained growing attention in the last years. The evaluation of the acoustic impact of shipping activity (as well as of other anthropogenic noise types) on marine fauna has become an important issue for society and regulators. The normative framework on the subject is not yet in place, but it is in rapid evolution and in the process of being finalized soon, as reflected by the research efforts being deployed on the subject by the E.U. (see the completed SILENV project and the ongoing AQUO and SONIC projects). In parallel, at an international level, the same subject has been covered by the International Maritime Organisation (IMO) through the activity of a dedicated Working Group. A key aspect of the control problem for URN from ships is a proper characterization of the source represented by the vessel. This item presents peculiar aspects due to the environment in which radiation occurs, but it is also driven by the complex features and large dimensions of the ship source. An important issue is the directivity of the emission, which influences: the patterns of the radiation, the distance at which the presence of the ship is perceived and the acoustic impact of the vessel. In this paper, experimental surveys performed at sea within the SILENV project are analysed to derive the directivity patterns of different ships in different conditions at different frequencies. The work covers the measurement procedure adopted, as well as the post-processing techniques and the uncertainties affecting the results.

The underwater noise radiated by ships has been with increasing emphasis included in the list of emissions into the ambient that need to be evaluated and controlled. While from point of view of international treaties and conventions this general goal is now well assessed, from a technical point of view the quantification of the impact of underwater noise emissions from ships is not yet consolidated. The general increase of the background noise in the oceans due to the diffused shipping activity is an objective datum, but how this noise is radiated by ships and how it affects globally and locally the marine wildlife are not yet clear subjects. From the point of view of the models to be used for the assessment, two areas in particular present significant uncertainties: the characterisation of the ship source and the quantification of the noise effects on the marine fauna. Both aspects need to be handled at an experimental level and they are intimately connected, as a proper characterisation of the source levels depends on which effects of the radiation need to be modelled. The paper focuses on the present situation in the two fields, highlighting the areas that still need to be investigated in order to set a consistent normative framework for achieving the objectives.

The rising concern about the environmental impact of ship noise on the marine fauna recently pushed national and international bodies to face the problem. In the last decade a few mass strandings of cetaceans due to sea trials of navy sonars (Frantzis (1998)), enforced the interest on noise pollution effects on marine mammals. The problem of evaluating the impact of underwater noise from ships is very complex due to the difficulties in characterising the whole noise chain (source, transmission path, receiver). Standards have been recently issued aimed at the measurement of underwater noise emitted from commercial ships. As regards the transmission path, problems are linked to the correct evaluation of the transmission loss which is influenced by many environmental parameters (water temperature, salinity, pressure, bottom composition etc.) which cannot be easily monitored during measurements. Finally the actual sensibility to noise of the marine mammals it is not completely known, especially for species belonging to the Mysticetes (Baleen Whales). These problems have been analysed in the SILENV collaborative project (Ships oriented Innovative soLutions to rEduce Noise & Vibrations), devoted to the holistic analysis of noise emissions from the ship [radiation inside the ship and outside (in air and in water)].

Noise pollution is an important part of the environmental impact of ships. The noise inside the vessel (affecting crew and passengers) has been regulated since a few decades, while the impact of emissions in water on the marine fauna has been under consideration at the International Maritime Organisation (IMO) only in the last few years. No specific effort seems to be in place towards a regulatory framework for external airborne noise emissions from sea going commercial ships. Only the particular cases of inland vessels and pleasure crafts are partially covered by rules. The airborne noise pollution from commercial ships, on the other hand, does affect people living near channels, in coastal areas with intense traffic or near ports, where ships enter and stay at wharf for loading/unloading processes. The actual dimension of the problem is remarked by several cases of complaints sent out by citizens living in the urban areas affected. Within the SILENV project (Ships oriented Innovative soLutions to rEduce Noise & Vibrations, funded by the E.U.) assessment criteria for the airborne noise emitted by sea-going ships have been proposed: the background information, the general criteria at the basis of the formulation, the aims as well as the verification procedure of the proposed limits are discussed in the paper.

The issue of the environmental impact of shipping activities is treated in this work from the specific viewpoint of underwater noise emissions from the vessels. There has been recently a rising concern about the negative effects that this kind of emissions can have on the marine wildlife in general and in particular on marine mammals. In these animals, acoustic communication and perception has acquired a privileged role compared with other senses and other zoological groups. The paper examines the role in this scenario of noise emissions from shipping and explores how their impact can be quantified, in order to establish a target for the control of such emissions. The standards recently issued for the characterisation of underwater noise signature by commercial vessels are also reviewed. The paper builds on the first results of the project SILENV, funded with the 7th Framework programme of the European Union

In this work the problem of underwater radiated noise emitted by cavitating propellers is addressed, considering the case of single screw ships. To this aim, a series of experimental results obtained in model and full scale is presented. The analysis of results reported allows to discuss the effect of the surrounding ambient in model scale measurements and the importance of a correct representation of the ship wake. A comparison of model and full scale measurements is also reported.

The problem of the impact of airborne noise emitted by commercial ships moored at quay is gaining attention by Regulatory Bodies. The question is often raised by citizens sending complaints to the municipalities of port cities in which the harbour is located inside the town. The problem may be even more important in the case of pleasure crafts accessing protected areas and mooring there. Limit levels for airborne noise emissions started therefore to be fixed in normative as well as contract requirements. In the light of what above, an effective measurement procedure to characterise the noise emissions from ships and compare them to limits plays an important role. The procedure needs to take into account aspects linked to the ship source characteristics (dimensions, complexity, directivity) as well as related to the surrounding environment, which is often represented by the shipyard where the ship is built. The latter aspect includes the presence of obstacles and reflecting surfaces around the ship, as well as significant components of background noise. The paper recalls the background of a measurement procedure that was defined within the project SILENV of the 7th Framework Programme specifically for the purpose of the characterisation of ships as airborne noise sources and reports a trial application of this procedure to a ship moored at a yard quay. Instrumentation used and data post processing are discussed, together with practical problems encountered and solutions found in order to carry out measurements.

The requirement of better workers' psychophysical health and the wish to guarantee a correct comfort also during work activities, induce to consider the presence of significant pure tones also for the working spaces. However, the current European legislation regarding professional exposure to the noise of the workers, and namely the EU Directive 2003/10/CE, does not take into consideration the possible presence of pure tones in working noise. The same lack can be noticed in the standard ISO 1999:2013. As regards seafarers, the reference codes are the International Maritime Organization (IMO) Resolution A.468(XII) for ships built before 1 July 2014, and Resolution MSC.337(91) for newer ships. While tonal components are mentioned in the first one, stating that, if these are "obvious", the ISO noise rating (NR) number should be also determined, in the latter and most recent IMO Resolution no reference to tonal components is present. Tonal components cause annoyance and, at the same time, they induce hearing damage and can alter the behavior of workers, with a potential risk for the safety of ships. In this study, noise measurements taken onboard different ships are analyzed in order to determine seafarers' work exposure to tonal components. The survey includes different work spaces. To assess the presence of tonal components in crew's work environments the methodology of environmental noise analysis, defined in the Annex B of Italian Decree D.M. 16/3/98, has been used, making reference to ISO 226:2003 for determining normal equal-loudness level contours. The method used in order to evaluate tonal components is well established for the environmental noise annoyance and therefore it can be operatively extended to the workplace noise exposure. Results show that the presence of tonal disturbing components is not sporadic and therefore worthy of further analysis and regulation.

A growing attention has been recently devoted to the impact of the underwater noise field generated by shipping activities on the marine fauna. A key aspect for the quantification of such impact is a proper model of the source levels radiated from the vessels. At a first level of approximation, simplified formulations based on a small number of macro-parameters describing the ship characteristics are needed to quantify the emission and, accordingly, assess the noise impact and evaluate strategies for its control. In fact, a few models of this kind are available in literature, mainly based on measurements and databases developed for military purposes. Most of these models have been tuned on old ships: this poses the question whether they are still applicable to modern commercial vessels. In the present work, spectra of a series of measurements of underwater noise emitted by commercial vessels measured in the framework of two EU FP7 projects (SILENV: www.silenv.eu and AQUO: www.aquo.eu) are analyzed and compared with the results obtained applying the available literature models. The analysis is carried out for noise emitted both at design and off-design conditions. In such conditions, the models are also compared with a proposed spectral parametrization. Focusing on the off-design conditions, a detailed narrow band analysis of a complete set of noise spectra is presented for a ship equipped with a controllable pitch propeller (CPP). The spectral peculiarities of such a propulsion plant, when operated at constant revolutions per minute (RPM) are highlighted. Results of the suggested parametrization applied to the same ship are presented together with the data of other CPP ships and a critical analysis is carried out discussing the limits of the existing predictive models.

There is a rising concern about the environmental status of the seas of our planet. Such concern regards several kinds of anthropogenic activities and their impact on the marine ecosystems. Part of the adverse effects are recognised to be due to various forms of acoustic emissions generated by human activities related to the exploitation of sea resources and to shipping. The main regulatory bodies at international level, in the last decade, have started to look into the problem with the aim of monitoring the environmental status of marine waters, in particular the acoustical aspects) identify the situations where the anthropogenic impact is most intrusive and study and promote future actions for its control and reduction. The present work reports about the development and validation of a simulation tool able to predict the noise field generated by a set of ships sailing in a specific area. The simulation is based on real traffic data derived from the Automatic Identification System (AIS) normally used to monitor shipping traffic and on specific data characterising the environment of the zone of interest. The tool is meant to provide the Regulator with a means to study the present situation (with on-line AIS data) and/or study the effectiveness of possible measures devoted to reduce the acoustical impact of shipping by design and/or operative requirements. Motivation, bases and characteristics of the developed procedure are described in the paper, where a first validation of the tool is presented on the basis of data regarding a sea area off Barcelona (Spain). Data include AIS records, environmental parameters and underwater sound levels surveyed by an hydrophone placed in the area. The work has been developed in the framework of the collaborative project AQUO (Achieve QUieter Oceans by shipping noise footprint reduction), funded by the European Commission within a call of the 7th Framework Programme dedicated to the assessment and mitigation of noise impacts of the maritime transport on the marine environment, coordinated topic “The Ocean of Tomorrow”.

This paper presents spectral analyses of the underwater noise radiated by ships equipped with controllable pitch propellers. The noise measurements were performed at sea for three different ship's types. Each ship passage was characterized by a specific combination of propeller rotational speed and propeller pitch, allowing to investigate the variations of the radiated noise spectrum at different settings of the pitch-RPM combination law. Neglecting the low-frequency contributions, the focus is on the analysis of the broadband patterns in the range 100 Hz to 4 kHz A parameterization derived from a basic spectral pattern is adopted: the noise spectrum shape is approximated with a flat level magnitude up to a reasonable frequency followed by a logarithmic decay. An investigation of the relationship between the considered parameters and the actual ship condition is proposed along with a comparison with the predictions provided by classic Ross and Whales-Heitmeyer ship noise models.

In the present study, full-scale noise levels measurements on board a Ro-Pax ferry have been carried out in various compartments of the ship, both in stationary conditions (navigation) and during manoeuvres. Noise levels have been surveyed in various categories of spaces located in all decks accessible to both passengers and crew, with the purpose of giving a complete and effective picture of the acoustic climate on board. The measured noise levels have been compared with current and proposed limits for working and living spaces, obtaining a clear identification of the most critical spaces on board the ship both in respect to acoustic comfort and noise exposure of crew during working hours. In cabins, different operating conditions for air conditioning have been tested, to analyse the specific contribution to annoyance of the ventilation noise, which turned out to be in many cases determinant. Transient conditions during manoeuvres entering and leaving harbours have been analysed by spectral time histories in cabins and public spaces close to the main propulsion plant and to bow thrusters. These situations correspond to considerably high levels, which may limit significantly operation during night time.

Transports are well known to be major contributors to noise pollution. Noise and vibrations (N&V) abatement naturally appears as an important objective for the greening of surface transports. The SILENV project is a response to this requirement for the maritime domain. The consequences of N&V emissions from the ships are multiple. N&V emissions constitute a disturbance for both passengers and harbour area residents, and in some cases it may be a health issue for crew members. Moreover, the increasing ship traffic-generated underwater noise causes ecological nuisances on marine wildlife. The project assesses the problem of reducing the shipgenerated Noise & Vibration pollution with a holistic approach. After a definition of realistic target levels, existing experimental data from main types of ships and on-site measurements have been analysed to identify the most critical sources of noise and vibration. Innovative solutions have been individually assessed on technical and economical criteria. Finally a pre-normative requirements formulation, called “Green Label”, is presented, aiming at reducing the noise inside the ships as well as outside in air and water.

The problem of noise annoyance on board ships has been addressed since a long time. The first document setting limits on onboard noise was the "Code on noise levels on board ships", issued by the International Maritime Organisation in 1981. More recently all the major Classification Societies introduced in their requirements the so called "Comfort Classes". They generally provide different ratings of the acoustic comfort of ships. The growing needs of passengers and workers for acoustical comfort on board pushed both Classification Societies and IMO to consider an update of limits and criteria for noise annoyance assessment. The normative framework in the field is therefore presently in an evolution phase. In the present work, a series of existing measurements of noise carried out on a set of Ro-Pax vessels is analysed and compared with the existing requirements and with the new proposals of the SILENV collaborative project (Ships oriented Innovative soLutions to rEduce Noise & Vibrations), funded within the 7th Framework Programme of the E.U. and running in the period 2009-2012. The comparison provides an indication of the possibility for shipbuilding to cope with the new requests in terms of noise performances, provided that such requests are inserted in the design process. Further efforts are needed similar to those already implemented to fulfill the present formulations of compulsory requirements and reflected in the measured values.

One of the aims of the SILENV project, funded by the E.U. within the 7FP, was the development of prenormative requirements regarding the impact of shipradiated noise into three different environments: onboard the vessel and outside it, in air and in water. The paper describes the background of the new formulations which generally take into account the existing requirements, the technical know-how in the field of ship construction about the characterization of noise source and transmission paths and the actual knowledge of the way noise affects the various categories of receivers involved. On these bases, objectives of the noise control are defined in the various areas and the final choices in terms of limits are reported, also highlighting the motivations at the basis of the requirements. Possible future trends in the redefinition of objectives for the control of noise and in normative developments are also discussed.

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.

The noise generated by ships affects a wide range of receivers: crew and passengers inside the vessel, inhabitants of the coastal areas and marine fauna outside it. The time elapsed since these types of impact have been considered and the state of the art of the noise control for each of these fields is very different. The paper aims at analysing the regulatory frameworks in the various fields, underlining differences in the present level of development and suggesting possible improvements in the general approach. The paper refers to the first phase of the SILENV collaborative project (EU 7th Framework Programme).

The evaluation of the acoustic impact of ships is a complex problem, involving not only different sources but also different kinds of receivers and transmission paths. The problem of health and comfort for crew and passengers on board has been considered since a few decades, leading to quite a structured and detailed framework of Norms and Requirements. On the other hand, only in recent years a growing attention has been devoted to air-borne noise emissions outside the ship, for which requirements are not present. Underwater noise emissions have, even more recently, gained attention for their potential interference with mammals' communications and with the sophisticated use such animals make of acoustic signals for interacting with their living environment. An aim of the present work is to review the state of the art in the three areas above identified outlining the differences in the specific fields as regards: The present knowledge of the phenomena involved; the accuracy of the models available for the description of noise propagation; the accuracy of the models available for the quantification of noise effects.

Airborne noise emissions from ships can be a significant source of annoyance. Therefore, it is important to accurately predict ship noise in order to get an effective environmental noise control in planning new ports, or in widening existing harbor, or in locating new mooring positions. To test the reliability of current commercial simulators in predicting the noise field from complex sources such as ships, in the present work the airborne noise propagation from two different vessels was modelled: a Multipurpose Ship and a Fishing Research Vessel. The development of the model for both ships was performed in five steps: acquisition of the input data; modelling of the ship in the sound propagation software; definition of the noise sources; model validation; output data generation. Simulated data were then compared with on field measurements. The obtained results rise some questions about the measurement techniques adopted to characterize the source levels and the validation data, the simplifications made on the ship surface and the typologies of sources utilized in the study. Future developments in numerical simulators are needed in order to better describe outdoor noise propagation from ships, taking into account the specific nature and complexity of such sources.

Marine and offshore regulations about onboard noise are quite stratified and tangled, being issued by a number of international and national bodies. At the same time, many of the requirements are actually expressed in non quantitative terms and neglect parameters like noise spectra, low frequency pulsations or sound reverberation, which deeply influence the “sound wellness”. Aim of this paper is therefore to improve present requirements by introducing more meaningful noise annoyance criteria. These new criteria should be at the same time able to better express the actual reactions to noise from crew and passengers and simple enough to be widely applied on board ships. Such enhanced criteria are derived from the noise rating methods provided to rate indoor background sound in the civil engineering context. The possibility to make use of these indicators in the naval field is analyzed and some recommendations for a proper application on ships are given.