CONTROL OF AIRBORNE NOISE EMISSIONS FROM SHIPS A. Badino 1, D. Borelli 1, T. Gaggero 2, E. Rizzuto 3, C. Schenone 1

Transcription

1 CONTROL OF AIRBORNE NOISE EMISSIONS FROM SHIPS A. Badino 1, D. Borelli 1, T. Gaggero 2, E. Rizzuto 3, C. Schenone 1 1 DIME, University of Genova, Italy, aglaia.badino@unige.it, davide.borelli@unige.it, corrado.schenone@unige.it 2 DINET, University of Genova, Italy, tomaso.gaggero@unige.it 3 DICCA, University of Genova, Italy, enrico.rizzuto@unige.it ABSTRACT 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. Keywords: SILENV project, noise pollution, airborne noise, ship noise 1. INTRODUCTION An assessment of the environmental impact of ships involves consideration of different kind of emissions both in air and in water. Significant efforts have been dedicated in the last decades by international Normative Bodies to the control and mitigation of the effects of such emissions. As regards specifically the noise impact of ships, as pointed out in (Badino et al., 2011), the situation of the normative framework is pretty much different in the various types of ambient involved. The noise radiation towards the spaces internal to the vessel has been covered since a long time by Norms regarding the preservation of acceptable working conditions for the crew on board (IMO, 1981). Staring in the 90thies, requirements have been issued by Classification Societies (generally termed Comfort Classes) having the target of assessing the comfort of passengers and crew as regards noise levels on board (as well as vibration levels and other aspects). The subject of noise radiated by ships into water started to be considered only recently at IMO, see (IMO, 2007, 2009b, 2009c, 2010) and gained momentum also at European level with the launch of dedicated research programs (SILENV 2009, AQUO 2012). As mentioned in (Badino et al., 2011), the control of airborne emissions from ships and the assessment of their impact on the external environment has not been faced so far at an international level, despite the fact that such impact results to be significant on the inhabitants of living areas near channels, near coastal waters with intense traffic or near ports, both during the approach of ships and the period spent at wharf for loading/unloading processes. On the other hand, the problem has been often tackled at a local level and with different approaches by local administrations, driven by complaints sent out by citizens living in the areas affected. As pointed out in the cited paper, the lack of coverage of this aspect by international normative bodies is probably due to the fact that the assessment of the impact of the noise emitted by ships during coastal operations depends not only on the ship, but also on the characteristics of the coastal area (orography, urbanistics). Accordingly, the Bodies involved in the assessment and the control include quite different institutions at an international as well as local level: (e.g. IMO, Class Societies, Port Authorities, Municipalities, etc.). This makes difficult a co-ordinated normative approach. Notwithstanding what above, a qualified objective of the SILENV project was to set goals for limiting the various types of noise impact by ships revising and, when appropriate, defining limits to be fulfilled in the design process of the vessel. The present paper describes how this objective has been sought and obtained, with specific reference to the external airborne noise emissions by seagoing ships. 21

2 2. EXISTING REQUIREMENTS IN SIMILAR CASES Prior to formulate a requirement for ship emissions it is worthwhile to recall the requirements already enforced in different fields but covering similar aspects of airborne noise pollution. They will be briefly analysed in the following. 2.1 EUROPEAN UNION DIRECTIVES The Directive 2002/49/EC is aimed at quantifying the noise impact in the short, medium and long term of major sources (roads, rail and aircraft: vehicles and infrastructures, industrial plants, equipments and mobile machineries). The indicator used is the L DEN defined as follows: L DEN 1 10lg L L 5 L 10 day evening night (1) where L day, L evening, L night are the A-weighted longterm average sound levels determined over all the day, evening, night periods of a year. These limits are meant to be verified at the border of the industrial area of interest in the closest position that a common inhabitant of the surrounding areas can access. The levels actually present in the mentioned position, however, are highly dependent on the local geography of the area; in particular for a ship at harbour, relevant aspects would be: position of the quay where the ship is moored, of the surrounding buildings, altimetry of the area (all affecting the transmission losses from the ship to the receivers). The L DEN values do not characterise a source in itself, but the source in a specific ambient and is therefore a quantity non particularly suitable for a use in a design phase when specific environmental conditions are not available. The Directive 2006/87/EC, regarding inland navigation vessels, provides, on the contrary, limits expressed in db(a) levels. In particular Article 8.10 Noise emitted by vessels reads: 1. The noise produced by a vessel under way, and in particular the engine air intake and exhaust noises, shall be damped by using appropriate means. The noise generated by a vessel under way shall not exceed 75 db(a) at a lateral distance of 25 m from the ship's side. 3. Apart from transhipment operations the noise generated by a stationary vessel shall not exceed 65 db(a) at a lateral distance of 25 m from the ship's side. As apparent, in this second directive requirements are explicitly devoted to limit the noise generated by vessels at source, in both the conditions of ship at Figure 1: Measurement surface for sources with large dimensions (from ISO 3746:2010). quay and ship sailing. It is to be noted that transhipment operations (loading/unloading) are excluded. 2.2 TECHNICAL STANDARDS A significant reference for the characterisation of large sources placed on a reflecting plane is given in ISO from which Figure 1 is taken. The standard refers to the determination of sound power levels by sound pressure surveys carried out on a measurement surface in the proximity of a static source, as a moored ship can be considered. In the Figure a parallelepiped surface is shown. The aim of the present investigation is not a characterisation in terms of power radiation of the ship, but the same criteria for the definition of a representative measurement surface around the source and of the grid of point to be placed on it can very well be adapted to the case of the ship moored at quay. Other interesting measurement standards (referring to vehicles in motion) are contained in the ISO 2922:2000 regarding the airborne sound emitted by vessels for inland navigation, in motion and at harbour. The suggested characterisation in this case is represented by a single measurement point at 255m from the vessel at an height of 3.5 m over the water surface. The same approach is contained in ISO :2008, referring to pleasure boats in motion. The procedure consists in a pass by test with the configuration represented in Figure 2. The same reference distance and vertical position as for inland vessels apply. Very similar arrangements are used also for other vehicles, like trains, cars, motorcycles or trucks: see for trains Figure 3, taken from ISO 3095:

3 microphone Figure 2: Pass by test measurement layout modified from ISO :2009 vertical view. The distance from the source adopted in the standards depends on the vehicle typology, due to the different dimensions and also to the different situation in predicting and tracking the actual trajectory of the vehicle during the test. On the other hand, some common features can be identified among the various procedures: a) a single measurement position is selected along the path followed by the moving vehicle (controlling the time duration of the survey a scan of the vehicle emission along its longitudinal axis is obtained), b) maximum sound pressure level during pass-by test is adopted as emitted noise indicator and c) the vertical position is chosen in order to cover the presence of local sources in the upper part of the unit (this is explicitly mentioned in the ISO 3095, with 2 microphones foreseen in the test: Figure 3). 3. SCOPE OF THE PRESENT ANALYSIS The present analysis focuses on seagoing vessels and aims at setting limits on the noise radiation at source that can be effective in reducing the impact of such radiation on the exposed population of coastal areas. 3.1 STRATEGIES IN DEFINING LIMITS craft In principle, to reach the goal of controlling the impact of noise on close living areas, limits could be set directly at the receiving position where the control of noise effects is needed. This is the strategy followed by the Directive 2002/49/EC above recalled, which is however best suited in the assessment of an existing plant, when details of the areas surrounding the source are available. At a design level, an approach based on the limitation of the emission at source is more suitable, even Figure 3: Arrangement for pass by tests on trains, from ISO though the final impact of noise radiation will depend also on the surrounding environment. Characterising and limiting the emission source is, in short, only a part of the whole problem of controlling noise effects, but, on the other hand, is the only one that can be developed at a design phase of the system which represents the source. It is also worthwhile noting that dealing with a known source allows to seek the final goal also by means of operative constraints (in the case of the ship: speed limitations, distance from the shore, manoeuvring speed, time limitations, location within the harbour) that can be imposed depending on the source strength. A proper characterisation and control of the ship source levels is therefore to be intended as a key point of the control of port noise. With this in mind, within the SILENV project experimental characterisation procedures and reference levels for airborne emissions from ships were set, which, together with analogous limits on emissions in water and on the propagation towards the internal spaces of the ship make up the socalled green label requirement with respect to noise emissions. 3.2 CHARACTERISTICS OF THE SHIP AS A NOISE SOURCE The ship is a complex source of airborne radiated noise. Many single sources can contribute to the general noise emission, each one with different characteristics. Structure-borne sources internal to the ship (in particular the propulsion engines) can excite vibrations in the hull (or in portions of it) and in turn this can generate noise waves in air. This radiation mechanism, however, is not very effective at larger distances, while affecting significantly people on board the vessel (in the internal spaces or on the decks). More effective from the viewpoint of the propagation outside the vessel are the sources of airborne noise that, even though placed inside the vessel, are however in communication with the surrounding ambient through openings. Examples of these sources are represented by the funnel, where exhaust gases at high speed are sent in the atmosphere from the exhaust system and inlet/outlet ducts belonging to heating, ventilation and air-conditioning (HVAC) systems. The above mentioned single sources are distributed along the entire ship both in the longitudinal and in the vertical direction (see Figure 4), generating a complex 3D noise field radiating from the ship. Moreover, different operating modes for the ship can be identified, each one characterised by different sources on board and/or different relative contributions to the total emission: a) ship sailing along the coast b) ship manoeuvring (entering/exiting the harbour) c) ship at quay (no cargo processing) d) ship loading or unloading (equipment for cargo processing in function) 23

4 Figure 1: Airborne noise source on ships. In a) the most important source is represented by the main propulsion engines and their related exhaust discharges. In b) the main engines are working in off-design conditions. Other manoeuvring equipment are in function (bow and stern thrusters, auxiliary azimuthal propulsors, winches, windlasses, etc.). In c) and d) the main engines are supposed not to be operating, while many of the auxiliaries are running. Case d) is characterised by specific noise components due to the operation of cranes, buckets, ramps and other charging/discharging means (which may produce noise with an impulsive nature or anyway peculiar frequency contents and/or durations). In the present context the focus is on operating modes a) and c), whose noise emission are in principle stationary and which are identifiable in a similar way for all types of ship (the other two being more dependent on the specific features of the single ship). 3.3 FEATURES OF THE NOISE FIELD RADIATED BY SHIPS Experimental surveys and predictions on the sound field radiated by ships at quay were carried out in the SILENV project. Figure 5 presents prediction results for a multipurpose ship see (Badino et al., 2012), while Figure 6 and Table 1 report the experimental results for the same ship obtained in a campaign carried out in the framework of the SILENV project by the High Technological Park Technical University of Varna (HTP-TUV). Aim of the campaign was to validate mathematical models Figure 6: Points surveyed during the experimental campaign. and to compare the existing vessels emitted levels with the preliminary target levels fixed at the beginning of the project. Other analogous data are available from literature see e.g. (Draganchev et al., 2012). It is quite clear that the near field sound radiation in the proximity of the ship is complex and need to be described carefully. The complexity arises from the presence on board of different sources interacting with several reflecting surfaces and a number diffracting edges existing on board and, possibly, on shore. The influence of the shadowing effect of the sidedeck connection on the propagation of noise from a source placed on the deck is visible both in Figure 5 and in Table 1. In Table 1 the colour scale highlights (in red) the presence in the two sections of strong sources on the deck (fans). Shadow cones close to the side are present at a lower height. The shape of the shadow cones is different in the two sections and the sound field appears not be regular at 19 m from the side (in the fore section the pressure levels keep on increasing with the distance from the ship up to 19 m). In Figure 7 a sketch is presented for the quantification of the influence of the shadowing effect of the side-deck connection on the propagation of noise from a source placed 1 m over the deck. Table 1: Recorded noise levels (db(a)) in the positions shown in Figure 6 Figure 5: Predicted noise field for a multipurpose ship Position horizontal vertical section in way of engine room fans (aft) section in way of cargo hold fans (fore) 19m 11m 1m 19m 11m 1m 6m m m

5 Figure 7: Sketch of the shadow zone generated by the hull s side for a source on the deck. The distance d (see Figure 5) that represents the limit of the shadow zone can be easily evaluated by the following expression: B d ( D T ) (2) 2 T= draught, D= depth, B= beam The situation may be different if measurements are carried out in the far field: at larger distances from the hull, the radiation features more regular patterns (see Figure 5). On the other hand, the distance at which a source can be considered as omnidirectional is by rule-of-thumb 7-8 times the dimension of the source. This, in the case of a ship, would bring the measurement location so far away as to make quite difficult to get a high enough signal to noise ratio. This very preliminary analysis suggests that measurements for a ship will most often be carried out in the near field and therefore a suitable spatial distribution (in particular in the vertical direction) of the survey positions is to be selected to capture the characteristic of the radiation field. What above is noted with reference to the ship at quay, but can be transferred also to the case of ship sailing. For the ship manoeuvring and loading/unloading the situation may be further complicated by time dependencies and random occurrences of the noise radiation. 4. REQUIREMENTS FOR SHIP AT QUAY The strategy that has been adopted to characterise the ship while floating still at quay is similar to the one of the ISO 3746:2010 above presented. In the present case, there is no need to adopt a closed measurement surface (no evaluation of the power emitted by the ship is sought). Accordingly, the top horizontal plane of the parallelepiped is omitted, as the noise radiated in the vertical direction propagates in a direction where no receivers are present. 4.1 POSITION OF THE MEASUREMENT SURFACE In defining a distance from the ship where the measurements surface is placed, both technical and practical aspects have been taken into account. A short distance from the ship is more practical because of easier accessibility. Moreover, the influence of possible reflections from surfaces external to the ship such as buildings, walls etc., is likely to be less pronounced in this position. Getting too close to the ship implies, however, to increase the resolution in the grid of measurement points, as the pressure field tends to become less homogeneous and needs a more detailed description. On the other hand, at larger distances from the ship side, such as the 25 m suggested in the European directive 2006/87/EC and in ISO 2922:2000, other drawbacks may arise: reflecting surfaces (e.g. buildings, cranes, containers etc) may be present, affecting the sound field, and background noise, coming from external sources in the area, can jeopardise the measurements. In the light of what above, a distance of 10 m from the ship sides (and from the bow and the stern) was set for the measurement surface. Such distance is suggested by practical as well as technical issues, as it is likely that for the major part of shipyard and port layouts this corridor along the ship side and the adjacent area is free of obstacles. Further, in the same space cranes are often located, which can be used to move a microphone in the measurement grid positions. From a technical point of view, the distance is large enough to allow for a grid of points not too dense (which would imply an increase in the measurement effort). The distance of 10 m is set with a small tolerance (0.5 m) in order to avoid the use of corrections to report the levels to the reference distance: the adoption of this possibility would have implied the definition of a transmission loss law which is not easily definable in the near field of the ship. The measurement surface, therefore, results to be composed of four vertical planes (two parallel to the ship s symmetry plane and two perpendicular to it see Figure 8 below) at the reference distance of m). 4.2 EXTENSION OF THE MEASUREMENT SURFACE The portion of the lateral area of the measurement parallelepiped to be covered by the grid of points, as suggested in ISO 3746:2010, should extend by 10 m (reference distance) beyond the maximum dimensions of the ship in the three directions of space. In particular the vertical extension is needed to overcome the above mentioned shadowing effect of the main deck. This is an important aspect because as pointed out by actual cases of complaints sent out by citizens near port area, very often the position where these negative noise effects were detected is often placed at higher levels than the ship deck (higher floors of buildings, or on hills surrounding the harbour). This highlights the importance of carrying out measurements also 25

6 (a) (b) would rely much on the subjective evaluation of the surveyor. To overcome this problem, a regular grid of points (with constant density) is placed on the measurement surface surrounding the ship. As regards the resolution of the grid, a balance is to be found between accuracy and measurement efforts. The distance between the measurement points is influenced by the dimension of the source and by the position of the measurement surface: the farer the surface is placed from the source, the coarser may be the grid of points on the surface (see ISO 3746:2010). In the light of these considerations, the spacing for the points was set as: d= 6 m for L<100 m d=10 m for L>100 m The first row from below is to be set at 1.2 m from the ground. These values seem to be a good compromise between accuracy of the measurements and their duration. 4.4 PRACTICAL CONSIDERATIONS Figure 8: Grid of points depending on the longitudinal profile of the ship. at high levels from the quay, in order to capture the most relevant noise components. As the longitudinal profile of ships may include portions of the weather deck at different levels (particularly in the presence of aft superstructures), the grid does not need to be rectangular in the longitudinal planes, but may follow the ship profile, provided it is extended by 10 m in vertical and longitudinal direction from each corner (Figure 8). Figure 8 sketches a part of the grid for two types of ship: a passenger ship (a) and a merchant ship (b). These two kinds of vessels respectively represent regular profile and irregularly shaped ships. Characterisation tests must be carried out on both sides of the ship, due to the possible asymmetry of the sound field radiated. 4.3 RESOLUTION OF THE GRID OF MEASUREMENT POINTS Due to the complex distribution of the noise sources on board, the measurements aimed at characterising the noise levels emitted by ships are to be carried out with a spatial resolution able to capture all the contributions and in particular to quantify properly the strongest ones. In principle, only a small number of measurements concentrated in the proximity of the (strongest) sources are needed, but both the sources location on board and their relative strength are not known a priori. Accordingly, an approach based on a small number of selected measurement positions on the reference surface would be efficient but For example, the number of measurement points for a passenger ship with L=300 m, B= 35 m and D=60 m, is around 500. This kind of measurements will be typically carried out in the shipyard where the vessel is built. A possible strategy consists in using a microphone array suspended from a crane (see Figure 9). This procedure allows to measure an entire vertical column of points at the same moment, with considerable savings of time. The other columns can be easily surveyed by moving the crane on the rails along the ship length without changing the jib configuration. 4.5 LIMIT LEVEL Based on the analysis of on field measurements and on the limit set for inland vessels at harbour in the directive 2006/87/EC (65 db(a) at 25 m), a provisional limit of 70 db(a) at 10 m from the ship was set as SILENV requirement. This value is not to be overcome in any of the measurement points. In respect to the above directive, a key difference is that measurements at different height are to be carried out, thus ensuring that all connection paths from the source to the possible receivers are covered. The value in itself is, on the basis of the measurements available, technically achievable by state of the art designs, but on the other hand, seems to be restrictive enough to filter away particularly annoying situations. It is here noted that the same limit, to be verified at the border of industrial areas, is typical of European regulations at national level (see f.i. Italy s DPCM 1997). The same value is also set as SILENV limit for open spaces on board ships (people on decks may however be shielded more by e.g. funnel emissions 26

7 than other people ashore, so the requirement is not to be considered as redundant) 4.6 SIMPLIFIED PROCEDURE What above described represents the suggested procedure for a proper characterization and limitation of the noise radiation from a moored ship. Within the SILENV requirement, it was decided to set an alternative criterion, that can be accepted when it is impossible to carry out measurements on the parallelepiped surface. According to this simplified procedure, measurements can be carried out in an horizontal line of points at ground level (at least 1.2 m over the quay) at 25 m from the ship side (see Figure 10). The longitudinal spacing follows the general rule (see section 5.3 above). No obstacles must be present between the ship and the measurement rows. The limit set in this case is 60 db(a). It is lower (stricter) than the limit set on the complete grid for two reasons: it is to be verified at a larger distance from the ship and it takes into account that at ground level important contributions due to sources at higher levels may be underestimated. As in the case of the complete grid measurements, the procedure is to be repeated for both ship sides. 5. REQUIREMENTS FOR SHIP SAILING 5.1 PASS BY TESTS Figure 9: Possible measurements arrangement Figure 10: Measurement points for the simplified procedure. The existing standards for pass by tests of inland vessels (ISO 2922:2000) and pleasure crafts (ISO :2008) have been reviewed earlier in the paper. In both documents a single microphone placed at a distance of 25 m is used. The same reference is adopted in the directive 2006/87/EC to set the limit of noise radiation for inland vessels. In the following, the case of seagoing vessels is considered. Differences that can arise with the previously mentioned types of vessels are related with the dimensions of seagoing ships, in general larger, and in the arrangement of test. Inland vessels and pleasure crafts can be tested with a the microphone positioned ashore, while passing at the required distance from the channel side or the quay. For a large seagoing ship it might be necessary to carry out the test offshore (possibly combining this type of tests with sea trials); in any case it would be required for safety reasons to keep a larger distance from the recording position, placed either at sea or on quay. Must be noted that the noise indicator for pass by tests is the maximum level, L max, expressed in db(a), that is the higher sound pressure level measured at the microphone position while the ship is passing by. The SPL logging can be set at different intervals, being one second the most usual option. A further note regards the possible presence at 25 m of the same shadow zones that have been observed and commented for the noise radiated by the ship still at harbour. In comparison with the surveys of the ship in static conditions, on the other hand, pass by tests should be less exposed to the presence of obstacles (buildings and other deflecting or reflecting surfaces) and noise coming from external sources (particularly for tests at sea). Unfortunately experience on the subject of pass by tests was lacking in the project, so the final decision was to propose for L max the same limit that has been set for inland vessels, that is 75 db(a) at 25 27

8 m. Nevertheless the possibility of setting a larger distance, for example using Eq. 2 to avoid shadow zones, and a larger number of microphones, placed in a vertical array, may be considered. 5.2 SINGLE EVENT LEVEL AS A SAILING SHIP INDICATOR A further note regards the possible adoption of Single Event Levels (SEL) as quantity for reporting the results of the pass by test (and for the corresponding limits), as from long time for the airport noise. The quantity is actually defined in general terms also in the ISO 2922:2000 (see Eq.3), but could be adopted with the operative definition provided e.g. in CFR 14 for aircraft noise: p ( ) SEL 10log d T (1) p where T 0 is equal to 1s. The integration time ( 2-1 ) is determined with reference to the time history of the db(a) signal: a typical pattern is reported in Figure 11, showing a rising trend on the approach of the vessel and a decreasing part when the vessel starts to get farer. The portion of the curve comprised between the max db(a) value L Max and a horizontal line drawn 10 db(a) below it identifies the integration range. The SEL indicator takes into account the maximum noise level and the duration of the event and allows to compare noise from ships having different velocities and power levels, on the basis of the energy content of their emissions during the passby test. For ship events, the SEL value is always higher than the L Max value. From a general viewpoint, the SEL technique seems to be well suited for the purpose of characterising a sailing ship. On the other hand, the lack of data prevents at the moment from quantifying a proper noise limits for ships in terms of SEL. Figure 11: Definition of Single Event Level SEL integration domain 6. CONCLUSIONS The paper present the background of SILENV Green Label requirements regarding the airborne noise radiation by ships. Such requirements have been based on analogous ones already available for other classes of vehicles or static sources, but significant changes have been made on the characterisation procedure. These changes have been necessary to adapt the analysis to the case of seagoing ships and to make results more representative of the impact of airborne emissions from ships. The present version of requirements is subject to further development following the generation of a consistent database on the subject. ACKNOWLEDGEMENTS This work was developed in the frame of the collaborative project SILENV Ships oriented Innovative solutions to reduce Noise & Vibrations, funded by the E.U. within the Call FP7-SST RTD-1 Grant Agreement SCP8-GA REFERENCES Badino, A., Borelli, D., Gaggero, T., Rizzuto, E. & Schenone, C. (2011). Normative framework for noise emissions from ships: present situation and future trends Advances in Marine Structures Guedes Soares & Fricke (eds.) Taylor & Francis, London, pp , ISBN Badino, A., Borelli, D., Gaggero, T., Rizzuto, E. & Schenone, C. (2012). Modelling the Outdoor Noise Propagation for Different Ship Types, to be presented at NAV2012, 17 th International Conference on Ships and Shipping Research, Naples Oct CFR 14 (1984). Code of Federal Regulation, Title 14 Part 150 Airport Noise Compatibility Planning. Directive 2003/44/EC of The European Parliament and of The Council, 16 June Directive 2006/87/EC of The European Parliament and of The Council, 12 December DPCM 1997 Italy s Prime Minister Decree Determination of limit values of noise sources November 14, Draganchev H., Valchev S. and Pirovsky C. (2012) Experimental and Theoretical Research of Noise Emitted by Merchant Ships in Port Intern. Congress on Sound & Vibration ICSV19 Vilnius, LT, July 2012 IMO Resolution A.468(XII): Code on Noise Levels on Board Ships. IMO Document MEPC 57/INF.4 Shipping noise and Marine Mammals 28

9 IMO 2009a. Document DE 53/10, Proposals for the development of amendments to SOLAS regulation II-1/36 and a revision of the Code on noise levels on board ships. IMO 2009b. Document MEPC 59/19, Noise From Commercial Shipping and its Adverse Impacts on Marine Life IMO 2009c. Document MEPC 60/18, Noise From Commercial Shipping and its Adverse Impacts on Marine Life IMO Document MEPC 61/19, Noise From Commercial Shipping and its Adverse Impacts on Marine Life ISO Railway applications -- Acoustics - - Measurement of noise emitted by railbound vehicles ISO 2922:2000. Measurement of airborne sound emitted by vessels on inland waterways and harbours ISO 3746:2010. Determination of sound power levels of noise sources using sound pressure- Survey method using an enveloping measurement surface over a reflecting plane. ISO :2008. Small craft -- Airborne sound emitted by powered recreational craft -- Part 1: Pass-by measurement procedures ISO :2006. Small craft -- Airborne sound emitted by powered recreational craft -- Part 2: Sound assessment using reference craft SILENV D 1.2 (12/04/2010). Harbour noise nuisance. SILENV D (last version 31/12/2011). Test procedures for On-Site Measurements SILENV D (15/04/2012). Measurements Performance versus Requirements Comparison. SILENV internal document (26/4/2010). Comments on noise measurements procedures 29