Noise mitigation system

Abstract

The invention relates to a noise mitigation system configured for being suspended from a free floating vessel, wherein the noise mitigation system comprises: a noise mitigation screen configured to be positioned around a foundation element, in particular a (mono)pile, during driving the foundation element into an underwater ground formation, to reduce noise input resulting from the driving into the surrounding water, such as a river or sea, wherein the noise mitigation system further comprises a noise mitigation skirt configured to be positioned around the foundation element to reduce noise input resulting from the driving into the surrounding water and arranged at the lower side of the noise mitigation screen facing towards the underwater ground formation, and wherein the noise mitigation skirt is configured for extending from the lower side of the noise mitigation screen towards the underwater ground formation.

Description

[0001] NOISE MITIGATION SYSTEM

[0002] BACKGROUND

[0003] The invention relates to a noise mitigation system configured for being suspended from a vessel . Furthermore , the invention relates to a method for installing a foundation element, in particular a (mono ) pile, in an underwater ground formation by means of a driver .

[0004] Such a noise mitigation system, for example, is known from the European patent publication EP 3 084 093 , in which an underwater noise abatement and deployment system are described . The system uses inverted open-ended resonators , e . g . Helmholtz resonators , to absorb underwater noise . The system includes stackable resonator cavity embodiments arranged to surround a noisy environment or act nearby it . The system can be deployed from a ship or barge or similar structure, and can be stored when not in use .

[0005] SUMMARY OF THE INVENTION

[0006] During use of the known noise mitigation system, the system is deployed, for example, from a ship, wherein the system is suspended from the ship . The known noise mitigation system is suspended from the ship, such that the ship' s operator is able to perform an emergency relief of a monopile held by a gripper arranged at the ship in the unlikely event of a dangerous situation during installation of the monopile , and / or to keep tension in wires extending through the system in order to keep the noise mitigation system stable and / or in shape . In order to be able to release the monopile at all times during installation thereof , the bottom side of the known noise mitigation system, i . e . the side of the noise mitigation system facing towards the underwater ground formation, must be kept at a distance from the underwater ground formation, for example the seabed . This has to be understood as that the bottom side of the known noise mitigation system may not contact the underwater ground formation . Installation of such monopile usually is done by means of an impact hammer or by a vibro tool that drives the monopile into the underwater ground formation, while the noise mitigation system is surrounding the monopile . Due to the impact hammer hammering on top of the monopile, a shock wave is created within the monopile, which shock wave travels through the monopile from the top side to the bottom side thereof . At the location where the monopile enters the underwater ground formation, i . e . at the interface between the water and the underwater ground formation, as well as all along the monopile , the shock wave generates noise emitted into the surrounding water .

[0007] As the bottom side of the known noise mitigation system is placed at a distance from the underwater ground formation, a part of the monopile is not surrounded by the noise mitigation system, which is the part where noise is generated due to the interface between the water and underwater ground formation . This is disadvantageous , as the known noise mitigation screen still allows noise to be emitted unmitigated into the surrounding water .

[0008] It is an obj ect of the present invention to ameliorate or to eliminate one or more disadvantages of the known prior art , to provide an improved noise mitigation system or to at least provide an alternative noise mitigation system.

[0009] According to a first aspect , the invention provides for a noise mitigation system configured for being suspended from a free floating vessel , such as a ship or a barge, wherein the noise mitigation system comprises : a noise mitigation screen configured to be positioned around a foundation element, in particular a (mono ) pile, during driving the foundation element into an underwater ground formation, to reduce noise input resulting from the driving into the surrounding water, such as a river or sea, wherein the noise mitigation system further comprises a noise mitigation skirt configured to be positioned around the foundation element to reduce noise input resulting from the driving into the surrounding water and arranged at the lower side of the noise mitigation screen facing towards the underwater ground formation, and wherein the noise mitigation skirt is configured for extending from the lower side of the noise mitigation screen towards the underwater ground formation .

[0010] During use of the noise mitigation system according to the invention, the noise mitigation screen is placed into water in order to be positioned about a foundation element, such as a monopile . The noise mitigation screen, during use, remains suspended from the ship or barge , such that the lower side of the noise mitigation screen remains at a distance from the underwater ground formation, such as a seabed . As a result , the foundation element still may be released from the ship or barge when required . Further, the noise mitigation skirt extends from the lower side of the noise mitigation screen towards the seabed, while being positioned about the foundation element . As a result, the gap between the lower side of the noise mitigation screen and the seabed is at least partially covered by the noise mitigation skirt . This is advantageous , as the part of the monopile where noise is generated by the shockwave caused by driving the monopile and due to the interface between the water and seabed, is now at least partially covered by the noise mitigation skirt . Therefore , an advantage of the present invention is that the amount of noise emitted unmitigated into the surrounding water is reduced in comparison to the noise mitigation system according to the prior art .

[0011] In an embodiment, the noise mitigation skirt is moveable and / or is configured to be moved between a retracted position and an extended position, in which the noise mitigation skirt is enabled to reduce noise input resulting from the driving into the surrounding water . According to this embodiment, the noise mitigation skirt may be moved into the retracted position, for example, to transport the noise mitigation system, and into the extended position during use . An advantage of being able to move the noise mitigation skirt into the retracted position during transport , is that movement of the noise mitigation skirt with respect to the noise mitigation screen is limited or in the ideal case prevented . This is advantageous , as it prevents the noise mitigation skirt from being damaged during transport .

[0012] In an embodiment, the noise mitigation skirt is configured to be flexible while reducing noise input resulting from the driving into the surrounding water . During installing the monopile into the seabed, the ship or barge may move vertically as a result of waves occurring at the surface of the sea . As a result, the noise mitigation skirt may be moved vertically towards or away from the seabed . In case the noise mitigation skirt is moving towards the seabed, the noise mitigation skirt may contact the seabed . An advantage of the noise mitigation skirt being flexible is that such contact is absorbed by the noise mitigation skirt and does not result in damage to the noise mitigation system.

[0013] In an embodiment, the noise mitigation skirt comprises multiple noise mitigation skirt panels arranged next to each other . In an embodiment thereof , each of the multiple noise mitigation skirt panels is moveable between the retracted position and the extended position, preferably separately from each other . An advantage of this embodiment is that the noise mitigation skirt is enabled to follow irregularities of the seabed, such that the obtained noise mitigation ef fect remains as large as possible .

[0014] In an embodiment, each of the multiple noise mitigation skirt panels comprises an upper frame configured to be arranged at the lower side of the noise mitigation screen, a lower frame arranged moveable to the upper frame, and one or more connecting elements for connecting the upper frame and the lower frame to each other .

[0015] In an embodiment, each of the multiple noise mitigation skirt panels comprises a retracting device arranged at the upper frame thereof and operatively connected to the lower frame, wherein the retracting device is configured for retracting the lower frame towards the upper frame . Preferably, the retracting device comprises a drive, a driving axle extending therefrom, and a reel with retracting wire operatively connected to the lower frame . The retracting device according to this embodiment allows the lower frame to be moved into the extended position, in which the lower frame may move freely with respect to the upper frame because of the retracting wire . Further, the retracting device is also able to retract the lower frame towards and, optionally, against the upper frame in a reliable manner . An advantage of this embodiment , thus , is that extending and retracting the lower frame with respect to the upper frame may be done relatively simple in a reliable manner .

[0016] In an embodiment, each of the multiple noise mitigation skirt panels comprises a guiding device arranged at the upper frame and configured for guiding movement of the lower frame with respect to the upper frame . In an embodiment thereof , the guiding device comprises a guiding pin arranged at the upper frame and extending therefrom towards the lower frame . In an even further embodiment thereof , the guiding device comprises a guiding wheel , and the guiding pin is provided with a through hole, wherein the retracting wire is guided via the guiding wheel and the guiding pin towards the lower frame . According to this embodiment, the guiding wheel may be used advantageously for guiding the retracting wire in a reliable manner between the retracting device and the lower frame . Additionally, the guiding pin, during moving the lower frame into the retracted position, may be used for guiding the lower frame with respect to the upper frame , such that they may be placed properly with respect to each other .

[0017] In an embodiment, the lower frame comprises a rectangular frame portion and a triangular frame portion arranged at the side of the rectangular frame portion facing away from the upper frame and such that the apex thereof is facing away from the rectangular frame portion . In an embodiment thereof , the triangular frame portion comprises an apex rod defining the apex thereof , which apex rod is connected to the rectangular frame portion by means of connecting legs , and by means of partially open end caps arranged between the ends of the apex rod and the rectangular frame portion . An advantage of this construction is that the rectangular frame portion may remain substantially parallel to the seabed, even when the lower frame is placed on the seabed .

[0018] In an embodiment , when the guiding device comprises a guiding pin arranged at the upper frame and extending therefrom towards the lower frame, the lower frame comprises a receiver configured for receiving the guiding pin at least partially . In an embodiment thereof , the receiver comprises a receiving plate with a receiving opening arranged at the rectangular frame portion, wherein the receiving opening is configured for receiving the guiding pin when the lower frame is retracted towards or against the upper frame . When the lower frame is retracted towards the upper frame , the guiding pin is at least partially received within the receiving opening . As a result , movement of the lower frame is limited to movement along the longitudinal axis of the guiding pin and movement traverse thereto is substantially prevented . This is advantageous , as movement of the lower frame with respect to the upper frame while in the retracted position is kept to a minimum.

[0019] In an embodiment, the lower frame comprises a floater arranged thereat, wherein the floater is configured for granting buoyancy to the lower frame . The floater at the lower frame may be used advantageously for controlling the orientation of the lower frame while being in the water .

[0020] In an embodiment, the upper frame and / or the lower frame comprise one or more sound mitigators . In an embodiment thereof , the one or more sound mitigators are selected from a group comprising : open-ended resonators and air-filled elements .

[0021] In an embodiment, each of the multiple noise mitigation skirt panels comprises a sound mitigation member arranged between the upper frame and the lower frame and arranged, preferably fixedly, to the connecting elements . In an embodiment thereof , the sound mitigation member comprises one or more sound mitigators , wherein the one or more sound mitigators are selected from a group comprising : open-ended resonators and air- filled elements , optionally wherein the noise mitigation system comprises a flexible hose for supplying a gas , such as air, to the one or more sound mitigators . By providing a noise mitigation member between the upper frame and the lower frame, the sound mitigation effect achieved by the noise mitigation skirt advantageously becomes as large as possible .

[0022] According to a second aspect, the invention provides for a method for installing a foundation element, in particular a (mono ) pile, in an underwater ground formation by means of a driver, wherein the method comprises the steps of : providing a foundation element to be installed; providing the noise mitigation system; placing the foundation element on the underwater ground formation while gripping the foundation element ; placing the noise mitigation screen by suspending the noise mitigation screen from a free floating vessel , such as a ship or a barge ; and driving the foundation element into the underwater ground formation by means of a driver, while the noise mitigation screen is positioned about the foundation element, wherein the step of placing the noise mitigation screen comprises placing the noise mitigation skirt .

[0023] The method according to the invention has at least the same technical advantages as described in relation to the noise mitigation system according to the first aspect of the invention .

[0024] In an embodiment , wherein the noise mitigation skirt is moveable between a retracted position and an extended position, in which the noise mitigation skirt is enabled to reduce noise input resulting from the driving into the surrounding water, the method comprises moving the noise mitigation skirt into the extended position before or during the placing the noise mitigation screen, and / or moving the noise mitigation skirt into the retracted position before or during removing the noise mitigation screen from the foundation element .

[0025] The various aspects and features described and shown in the specification can be applied, individually, wherever possible . These individual aspects , in particular the aspects and features described in the attached dependent claims , can be made subj ect of divisional patent applications .

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings , in which :

[0028] Figures 1A and IB show a schematic overview and a cross-sectional view, respectively, of a noise mitigation system with a noise mitigation skirt according to an embodiment of the invention, suspended from a ship;

[0029] Figure 2 shows an isometric view of a part of the noise mitigation skirt of figure 1 , wherein the noise mitigation skirt comprises a number of noise mitigation skirt panels ;

[0030] Figure 3 shows an isometric view of a noise mitigation skirt panel of the noise mitigation skirt of figure 2 ; and

[0031] Figure 4 shows a cross-sectional view of the noise mitigation skirt panel of figure 3 .

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] A schematic overview of a noise mitigation system 1 according to an embodiment of the invention is shown in figures 1A and IB . As shown, the noise mitigation system 1 is suspended from a ship 2 provided with a crane 3 for lifting the noise mitigation system 1 and a foundation element, such as a monopile 4 . The ship 2 is further provided with a pile gripper 5, in particular a motion compensated pile gripper 5 , configured for gripping the monopile 4 during installation thereof in an underwater ground formation 6, such as a seabed .

[0034] Although not shown, an impact hammer may be arranged on top of the monopile 4 , which impact hammer is configured for hammering the monopile into the seabed 6.

[0035] The noise mitigation system 1 comprises a noise mitigation screen 10 configured to be placed around the monopile 4 , at least around the part of the monopile 4 within the water 7 , during driving the monopile 4 into the seabed 6 , to reduce noise input resulting from the driving into the surrounding water 7 . The noise mitigation screen 10 may be formed, as described in the European patent publication EP 3 084 093 , by means of large arrays of Helmholtz resonators , which are tuned to speci fic frequencies , to capture and mitigate noise caused by hammering the monopile 4 into the seabed 6. Alternatively, the noise mitigation screen 10 may be formed by a hydro sound damper (HSD) that comprises a net configured to be positioned around the monopile 4 . The HSD has a plurality of sound mitigating elements , such as balls filled with air, arranged within the net and positioned around the monopile 4 . Other types of sound mitigation screens 10 are also envisaged within the context of the present patent application .

[0036] Furthermore , as schematically indicated in figures 1A and IB, the noise mitigation system 1 comprises a noise mitigating skirt 11 arranged at the bottom side of the noise mitigating screen 10 . The noise mitigating skirt

[0037] 11 is configured for being positioned around the monopile 4 to reduce noise input resulting from the driving into the surrounding water 7 .

[0038] As best shown in figure 2 , the noise mitigation skirt 11 comprises a number of noise mitigation skirt panels 15 that are arranged at the bottom side of the noise mitigation screen 10 of the noise mitigation system 1 . The noise mitigation skirt panels 15 are arranged next to each other such that they surround the maj ority of the circumference of the monopile 4 .

[0039] A schematic view of a noise mitigation skirt panel 15 is shown in figure 3 . The noise mitigation skirt panel 15 has an upper frame 20 configured to be secured to the bottom side of the noise mitigation screen 10 , and a lower frame 21 that is arranged at the upper frame 20 at the side facing away from the bottom side of the noise mitigation screen 10 . The lower frame 21 is arranged at the upper frame 20 in a moveable manner by means of straps 22 , such that the lower frame 21 moves away from or towards the upper frame 20 in a direction substantially parallel to the longitudinal axis of the noise mitigation screen 10 .

[0040] The upper frame 20 comprises a rectangular frame portion 23 with spacing legs 24 arranged at the corners thereof , which spacing legs 24 extend from the rectangular frame portion 23 towards to bottom side of the noise mitigation screen 10 . Further, at a distance from each of the first and second ends of the rectangular frame portion 23 , a protecting plate 25 is provided that is connected to the rectangular frame portion 23 by securing legs 26 extending substantially parallel to the spacing legs 24 . The width of the protecting plates 25 is larger or slightly larger than the width of the rectangular frame portion 23 such that the protecting plates 25 extend beyond the longitudinal sides of the rectangular frame portion 23 when seen in a direction perpendicular thereto .

[0041] The upper frame 20 is further provided with 2 connectors 27 on each longitudinal side thereof for connecting the straps 22 to the upper frame , wherein the upper frame 20 has 4 connectors 27 in total . The connectors

[0042] 27 are arranged at a position corresponding to the position of the protecting plates 25 such that the connectors 27 are located below the protecting plates 25 when seen from above .

[0043] Additionally, the upper frame 20 includes guiding devices 28 arranged at a position corresponding to the position of the protection plates 25, such that a guiding device 28 is located below each of the protecting plates 25 when seen from above . Each of the guiding devices

[0044] 28 comprises a guiding wheel 29 located at the side of the rectangular frame portion 23 facing towards the bottom side of the noise mitigation screen 10 , and a guiding pin 30 having a through opening and extending from the upper frame

[0045] 20 towards the lower frame 21 .

[0046] At one of the longitudinal sides of the rectangular frame portion 23 , a retracting device 31 is arranged that is configured for retracting the lower frame

[0047] 21 towards the upper frame 20 . The retracing device 31 has a drive 32 , such as an electromotor, arranged between the guiding devices 28 at the longitudinal side of the rectangular frame portion 23 , and a driving axle 33 extending from both sides of the drive 32 towards the guiding devices 28 . A reel 34 with retracting wire 35 thereon is provided at each end of the driving axle 33 . The retracting wire 35 extends from the reel 34 over the guiding wheel 29 , through the guiding pin 30 , towards the lower frame 21 , to which the retracting wire 35 is connected . By operating the drive 32 , the lower frame 21 may be retracted towards the upper frame 20 or may be enabled to move away from the upper frame 20 .

[0048] Furthermore , a number of sound mitigators 36 , in this example inverted open-ended resonators , e . g . Helmholtz resonators , are arranged at the upper frame 20 to absorb underwater noise .

[0049] As best shown in figure 4 , the lower frame 21 comprises a further rectangular frame portion 40 arranged parallel to the rectangular frame portion 23 , and a triangular frame portion 41 arranged at the side of the further rectangular frame portion 40 facing away from the rectangular frame portion 23 , and such that the apex thereof is directed away from the further rectangular frame portion 40 . The triangular frame portion 41 has an apex rod 42 defining the apex of the triangular frame portion 41 , which apex rod 42 is connected to the further rectangular frame portion 40 by means of connecting legs 43 , and by means of partially open end caps 44 arranged between the ends of the apex rod 42 and the further rectangular frame portion 40 .

[0050] At the longitudinal sides of the further rectangular frame portion 40 , further connectors 45 are arranged that are aligned with the connectors 27 such that the further connectors 45 are arranged below the connectors 27 when seen from above . The further connectors 45 are arranged for connecting the straps 22 to the lower frame 21 . A receiving plate 46 with a receiving opening 47 is arranged between each of a pair of opposing further connectors 45, wherein the receiving opening 47 is configured for receiving the guiding pin 30 when the lower frame 21 is retracted towards or against the upper frame 20 .

[0051] As shown in figure 3 , a floater 48 is arranged on both longitudinal sides of the further rectangular frame portion 40 , wherein the floater 48 is configured for granting buoyancy to the lower frame 21 to keep the lower frame in a position in which the further rectangular frame portion 40 is substantially parallel to the seabed 6, even when the rod 42 is located on the seabed 6.

[0052] Moreover, a number of sound mitigators 36, in this example inverted open-ended resonators , e . g . Helmholtz resonators , are arranged at the lower frame 21 to absorb underwater noise .

[0053] Alternatively, in a not shown embodiment, the number of sound mitigators 36 may be formed by a Hydro Sound Damper (HSD) net with gas filled elastic balloons .

[0054] Each of the sound mitigation skirt panels 15 comprises a sound mitigation member 50 that is arranged between the upper frame 20 and the lower frame 21 and is connected to the straps 22 . In the shown embodiment, the sound mitigation member 50 comprises an intermediate frame 51 having an intermediate rectangular frame portion 52 . At the longitudinal sides of the intermediate rectangular frame portion 52 , intermediate connectors 53 are arranged for fixedly arranging the intermediate frame 51 to the straps 22 . An intermediate receiving plate 54 with a intermediate receiving opening 55 is arranged between each of a pair of opposing intermediate connectors 53 , wherein the intermediate receiving opening 55 is configured for receiving the guiding pin 30 when the intermediate frame 51 is retracted towards or against the upper frame 20 .

[0055] Moreover, a number of sound mitigators 36, in this example inverted open-ended resonators , e . g . Helmholtz resonators , are arranged at the intermediate frame 51 to absorb underwater noise .

[0056] During transport of the noise mitigation system 1 , the intermediate frame 51 and the lower frame 21 are retracted against the upper frame 20 by means of the retracting device 31 , while the intermediate frame 51 and the lower frame 21 are suspended from the upper frame 20 by means of the straps 22 during use of the noise mitigation system 1 such that the lower frame 21 and / or intermediate frame 51 may move towards the upper frame 20 when the lower frame 21 is located on the seabed 6 or contacts the seabed 6 because of movement of the ship 2 .

[0057] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention . From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention .

Claims

C L A I M S1 . Noise mitigation system configured for being suspended from a free floating vessel , such as a ship or a barge, wherein the noise mitigation system comprises : a noise mitigation screen configured to be positioned around a foundation element, in particular a (mono ) pile, during driving the foundation element into an underwater ground formation, to reduce noise input resulting from the driving into the surrounding water, such as a river or sea, wherein the noise mitigation system further comprises a noise mitigation skirt configured to be positioned around the foundation element to reduce noise input resulting from the driving into the surrounding water and arranged at the lower side of the noise mitigation screen facing towards the underwater ground formation, and wherein the noise mitigation skirt is configured for extending from the lower side of the noise mitigation screen towards the underwater ground formation, wherein the noise mitigation skirt is moveable and / or is configured to be moved between a retracted position and an extended position, in which the noise mitigation skirt is enabled to reduce noise input resulting from the driving into the surrounding water .2 . Noise mitigation system according to claim 1 , wherein the noise mitigation skirt is configured to be flexible while reducing noise input resulting from the driving into the surrounding water .3 . Noise mitigation system according to any one of the preceding claims , wherein the noise mitigation skirt comprises multiple noise mitigation skirt panels arranged next to each other .4 . Noise mitigation system according to claims 1 and 3 , wherein each of the multiple noise mitigation skirt panels is moveable between the retracted position and theextended position, preferably separately from each other .

5. Noise mitigation system according to claim 3 or 4 , wherein each of the multiple noise mitigation skirt panels comprises an upper frame configured to be arranged at the lower side of the noise mitigation screen, a lower frame arranged moveable to the upper frame , and one or more connecting elements for connecting the upper frame and the lower frame to each other .

6. Noise mitigation system according to claim 5 , wherein each of the multiple noise mitigation skirt panels comprises a retracting device arranged at the upper frame thereof and operatively connected to the lower frame , wherein the retracting device is configured for retracting the lower frame towards the upper frame .7 . Noise mitigation system according to claim 6 , wherein the retracting device comprises a drive, a driving axle extending therefrom, and a reel with retracting wire operatively connected to the lower frame .8 . Noise mitigation system according to any one of the claims 5-7 , wherein each of the multiple noise mitigation skirt panels comprises a guiding device arranged at the upper frame and configured for guiding movement of the lower frame with respect to the upper frame .

9. Noise mitigation system according to claim 8 , wherein the guiding device comprises a guiding pin arranged at the upper frame and extending therefrom towards the lower frame .10 . Noise mitigation system according to claim 7 and claim 9 , wherein the guiding device comprises a guiding wheel , and the guiding pin is provided with a through hole, wherein the retracting wire is guided via the guiding wheel and the guiding pin towards the lower frame .11 . Noise mitigation system according to any one of the claims 5- 10 , wherein the lower frame comprises a rectangular frame portion and a triangular frame portion arranged at the side of the rectangular frame portion facing away from the upper frame and such that the apexthereof is facing away from the rectangular frame portion .12 . Noise mitigation system according to claim 11 , wherein the triangular frame portion comprises an apex rod defining the apex thereof , which apex rod is connected to the rectangular frame portion by means of connecting legs , and by means of partially open end caps arranged between the ends of the apex rod and the rectangular frame portion .13 . Noise mitigation system according to claim 11 or 12 , when dependent on claim 9 , wherein the lower frame comprises a receiver configured for receiving the guiding pin at least partially .14 . Noise mitigation system according to claim 13 , wherein the receiver comprises a receiving plate with a receiving opening arranged at the rectangular frame portion, wherein the receiving opening is configured for receiving the guiding pin when the lower frame is retracted towards or against the upper frame .

15. Noise mitigation system according to any one of the claims 5- 14 , wherein the lower frame comprises a floater arranged thereat, wherein the floater is configured for granting buoyancy to the lower frame .

16. Noise mitigation system according to any one of the preceding claims 5- 15, wherein the upper frame and / or the lower frame comprise one or more sound mitigators .17 . Noise mitigation system according to any one of the preceding claims 5- 16 , wherein the one or more sound mitigators are selected from a group comprising : open-ended resonators and air- filled elements .18 . Noise mitigation system according to any one of the preceding claims 5-17 , wherein each of the multiple noise mitigation skirt panels comprises a sound mitigation member arranged between the upper frame and the lower frame and arranged, preferably fixedly, to the connecting elements .

19. Noise mitigation system according to claim18 , wherein the sound mitigation member comprises one or more sound mitigators , wherein the one or more sound mitigators are selected from a group comprising : open- ended resonators and air-filled elements , optionally wherein the noise mitigation system comprises a flexible hose for supplying a gas , such as air, to the one or more sound mitigators .20 . Method for installing a foundation element , in particular a (mono ) pile, in an underwater ground formation by means of a driver and a sound mitigation system according to any one of the preceding claims , wherein the method comprises the steps of : providing a foundation element to be installed; providing the noise mitigation system; placing the foundation element on the underwater ground formation while gripping the foundation element ; placing the noise mitigation screen by suspending the noise mitigation screen from a free floating vessel , such as a ship or barge ; and driving the foundation element into the underwater ground formation by means of a driver, while the noise mitigation screen is positioned about the foundation element, wherein the step of placing the noise mitigation screen comprises placing the noise mitigation skirt .21 . Method according to claim 20 , wherein the noise mitigation skirt is moveable between a retracted position and an extended position, in which the noise mitigation skirt is enabled to reduce noise input resulting from the driving into the surrounding water, wherein the method comprises moving the noise mitigation skirt into the extended position before or during the placing the noise mitigation screen, and / or moving the noise mitigation skirt into the retracted position before or during removing the noise mitigation screen from the foundation element .

Images