The Experts below are selected from a list of 561 Experts worldwide ranked by ideXlab platform

Nicole Kessissoglou - One of the best experts on this subject based on the ideXlab platform.

  • minimisation of the sound power radiated by a submarine through optimisation of its resonance changer
    Journal of Sound and Vibration, 2010
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou, Steffen Marburg
    Abstract:

    An important cause of sound radiation from a submarine in the low frequency range is fluctuating forces at the propeller. The forces are transmitted to the hull via the shaft and the fluid. Sound radiation occurs due to hull and propeller vibrations as well as dipole sound radiation caused by the operation of the propeller in a non-uniform wake. In order to minimise sound radiation caused by propeller forces, a hydraulic vibration attenuation device known as a resonance changer can be implemented in the propeller/Shafting System. In this work, cost functions that represent the overall radiated sound power are investigated, where the virtual stiffness, damping and mass of the resonance changer were chosen as design parameters. The minima of the cost functions are found by applying gradient based optimisation techniques. The finite element and boundary element methods are used to model the structure and the fluid, respectively. The adjoint operator is employed to calculate the sensitivity of the cost function to the design parameters. The influence of sound radiation due to propeller vibration on the optimisation of the resonance changer as well as the influence of the reduction in amplitude for higher harmonics of the blade-passing frequency on the control performance is investigated.

  • structural and acoustic responses of a submarine hull due to propeller forces
    Journal of Sound and Vibration, 2009
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou
    Abstract:

    Abstract The low frequency structural and acoustic responses of a simplified axisymmetric submarine model to fluctuating propeller forces along the submarine axis are investigated. The forces arise from a hydrodynamic mechanism and are transmitted from the propeller to the submarine hull through both the shaft and the fluid. Numerical models have been developed to simulate the strongly coupled structure–fluid interaction of a submerged vessel in the frequency domain. The structure is modelled using the finite element method, so that more complex features such as ring-stiffeners, bulkheads and the propulsion System can be taken into account. A simple, passive vibration attenuation System known as a resonance changer is included in the model of the propeller/Shafting System. The surrounding fluid is modelled using the boundary element method. The influence and importance of model parameters such as structural stiffness and fluid loading effects are investigated. Due to the fluctuating propeller forces, the hull is excited by axial structural forces transmitted through the propeller/Shafting System as well as by acoustic dipoles, where the dipoles are correlated to the structural forces in strength and direction. The acoustic dipole at the propeller also radiates sound directly to the far field of the surrounding fluid. It is demonstrated that the performance of the RC is negatively influenced at frequencies above the fundamental axial resonance of the hull by the effect of forces transmitted through the fluid. Another problem arises due to increased axial movement of the propeller, when the RC is optimised to minimise excitation of the hull via the propeller shaft. This results in an additional sound field that excites the submarine hull in a similar manner to the fluid forces that arise directly from the hydrodynamic mechanism.

  • reduction of the sound power radiated by a submarine using passive and active vibration control
    2009
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou, Steffen Marburg
    Abstract:

    As submarines can be detected due to their sound radiation, it is desired to minimise the radiated sound power. At low frequencies, submarine radiated noise is correlated to sound radiation from the propeller and the hull, where the hull is excited by propeller forces. In this paper, passive and active control of vibration is applied to a numerical model to reduce the low frequency sound radiation from a submarine. The performance of a control System using actuators that are tuned to the hull and propeller/Shafting System resonance is investigated. In addition, an optimised resonance changer is implemented in the propeller/Shafting System.

  • hull vibratory forces transmitted via the fluid and the shaft from a submarine propeller
    Ships and Offshore Structures, 2007
    Co-Authors: Roger Kinns, Iain Thompson, Nicole Kessissoglou
    Abstract:

    Abstract Disturbing forces due to a rotating propeller are transmitted to a ship or submarine hull via both the propeller shaft and the pressure field that is created in the surrounding water. This pressure field has hydrodynamic and acoustic components, because water is a compressible medium with a finite speed of sound. The work described in this article is a pilot study to investigate the combination of forces generated by the propeller motion that are transmitted to a submerged body. Fluctuating propeller forces are transmitted along the Shafting System to result in structural excitation of the submarine hull. These forces are also transmitted to the surrounding fluid and result in an external hull pressure field, because they correspond to acoustic dipoles. Both types of hull excitation contribute to hull vibration and underwater radiated noise. To demonstrate the fundamental nature of the problem, the case of a propeller located on the principal axis of a finite cylinder is considered, which represe...

  • hull vibratory forces transmitted via the fluid and the shaft from a submarine propeller
    HIPER 06: 5th International Conference on High-performance Marine Vehicles, 2006
    Co-Authors: Roger Kinns, Iain Thompson, Nicole Kessissoglou
    Abstract:

    Disturbing forces due to a rotating propeller are transmitted to a ship or submarine hull via both the propeller shaft and the pressure field that is created in the surrounding water. This pressure field has hydrodynamic and acoustic components, because water is a compressible medium with a finite speed of sound. The work described in this paper is a pilot study to investigate the combination of forces generated by the propeller motion that are transmitted to a submerged body. Fluctuating propeller forces are transmitted along the Shafting System to result in structural excitation of the submarine hull. These forces are also transmitted to the surrounding fluid and result in an external hull pressure field, because they correspond to acoustic dipoles. Both types of hull excitation contribute to hull vibration and underwater radiated noise. In order to demonstrate the fundamental nature of the problem, the case of a propeller located on the principal axis of a finite cylinder is considered, which represents a typical submarine arrangement. The analysis in this work has been simplified by considering only stationary fluctuating forces at the propeller hub and by regarding the propeller, hull and shaft as rigid structures. The relative magnitudes and phases of forces transmitted by the fluid and propeller shaft change with frequency in the range containing both low multiples of propeller blade passing frequency and broadband random components due to turbulent flow in the submarine wake. The effects of a finite speed of sound are found to be significant at low frequencies, causing changes in the hull forces that would be computed by assuming that water is incompressible. Results are presented describing the properties of acoustic dipole sources, which have both hydrodynamic and acoustic pressure fields that change in relative importance with distance from the source.

H. X. Hua - One of the best experts on this subject based on the ideXlab platform.

  • Longitudinal vibration of marine propeller-Shafting System induced by inflow turbulence
    Journal of Fluids and Structures, 2017
    Co-Authors: Ying Chen, L.-c. Wang, H. X. Hua
    Abstract:

    The multi-modal vibration characteristics of a ten-bladed marine propeller and its Shafting System induced by the inflow turbulence are numerically investigated. Firstly, the distributed pressure on the propeller face is computed by the correlation method according to the statistical characteristics of isotropic turbulence. Next, the mapped unsteady pressure is applied on the blades and the associated random vibration responses of the immersed elastic propeller and its Shafting System are computed by using the modal superposition method. Finally, vibration characteristics of the propeller and its unsteady thrust transmitted to the foundation are analyzed with different dynamic parameters of the System. The results show that amplification of the unsteady thrust associated with the low-order bending modes of the propeller blades cannot be neglected, especially when the frequency of the first bending mode approaches that of the longitudinal vibration mode of the Shafting System. The propeller with ‘soft’ blades suffers higher excitation intensity at its first natural frequency but the corresponding modal hydrodynamic damping may be enhanced.

Roger Kinns - One of the best experts on this subject based on the ideXlab platform.

  • minimisation of the sound power radiated by a submarine through optimisation of its resonance changer
    Journal of Sound and Vibration, 2010
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou, Steffen Marburg
    Abstract:

    An important cause of sound radiation from a submarine in the low frequency range is fluctuating forces at the propeller. The forces are transmitted to the hull via the shaft and the fluid. Sound radiation occurs due to hull and propeller vibrations as well as dipole sound radiation caused by the operation of the propeller in a non-uniform wake. In order to minimise sound radiation caused by propeller forces, a hydraulic vibration attenuation device known as a resonance changer can be implemented in the propeller/Shafting System. In this work, cost functions that represent the overall radiated sound power are investigated, where the virtual stiffness, damping and mass of the resonance changer were chosen as design parameters. The minima of the cost functions are found by applying gradient based optimisation techniques. The finite element and boundary element methods are used to model the structure and the fluid, respectively. The adjoint operator is employed to calculate the sensitivity of the cost function to the design parameters. The influence of sound radiation due to propeller vibration on the optimisation of the resonance changer as well as the influence of the reduction in amplitude for higher harmonics of the blade-passing frequency on the control performance is investigated.

  • structural and acoustic responses of a submarine hull due to propeller forces
    Journal of Sound and Vibration, 2009
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou
    Abstract:

    Abstract The low frequency structural and acoustic responses of a simplified axisymmetric submarine model to fluctuating propeller forces along the submarine axis are investigated. The forces arise from a hydrodynamic mechanism and are transmitted from the propeller to the submarine hull through both the shaft and the fluid. Numerical models have been developed to simulate the strongly coupled structure–fluid interaction of a submerged vessel in the frequency domain. The structure is modelled using the finite element method, so that more complex features such as ring-stiffeners, bulkheads and the propulsion System can be taken into account. A simple, passive vibration attenuation System known as a resonance changer is included in the model of the propeller/Shafting System. The surrounding fluid is modelled using the boundary element method. The influence and importance of model parameters such as structural stiffness and fluid loading effects are investigated. Due to the fluctuating propeller forces, the hull is excited by axial structural forces transmitted through the propeller/Shafting System as well as by acoustic dipoles, where the dipoles are correlated to the structural forces in strength and direction. The acoustic dipole at the propeller also radiates sound directly to the far field of the surrounding fluid. It is demonstrated that the performance of the RC is negatively influenced at frequencies above the fundamental axial resonance of the hull by the effect of forces transmitted through the fluid. Another problem arises due to increased axial movement of the propeller, when the RC is optimised to minimise excitation of the hull via the propeller shaft. This results in an additional sound field that excites the submarine hull in a similar manner to the fluid forces that arise directly from the hydrodynamic mechanism.

  • reduction of the sound power radiated by a submarine using passive and active vibration control
    2009
    Co-Authors: Sascha Merz, Roger Kinns, Nicole Kessissoglou, Steffen Marburg
    Abstract:

    As submarines can be detected due to their sound radiation, it is desired to minimise the radiated sound power. At low frequencies, submarine radiated noise is correlated to sound radiation from the propeller and the hull, where the hull is excited by propeller forces. In this paper, passive and active control of vibration is applied to a numerical model to reduce the low frequency sound radiation from a submarine. The performance of a control System using actuators that are tuned to the hull and propeller/Shafting System resonance is investigated. In addition, an optimised resonance changer is implemented in the propeller/Shafting System.

  • hull vibratory forces transmitted via the fluid and the shaft from a submarine propeller
    Ships and Offshore Structures, 2007
    Co-Authors: Roger Kinns, Iain Thompson, Nicole Kessissoglou
    Abstract:

    Abstract Disturbing forces due to a rotating propeller are transmitted to a ship or submarine hull via both the propeller shaft and the pressure field that is created in the surrounding water. This pressure field has hydrodynamic and acoustic components, because water is a compressible medium with a finite speed of sound. The work described in this article is a pilot study to investigate the combination of forces generated by the propeller motion that are transmitted to a submerged body. Fluctuating propeller forces are transmitted along the Shafting System to result in structural excitation of the submarine hull. These forces are also transmitted to the surrounding fluid and result in an external hull pressure field, because they correspond to acoustic dipoles. Both types of hull excitation contribute to hull vibration and underwater radiated noise. To demonstrate the fundamental nature of the problem, the case of a propeller located on the principal axis of a finite cylinder is considered, which represe...

  • hull vibratory forces transmitted via the fluid and the shaft from a submarine propeller
    HIPER 06: 5th International Conference on High-performance Marine Vehicles, 2006
    Co-Authors: Roger Kinns, Iain Thompson, Nicole Kessissoglou
    Abstract:

    Disturbing forces due to a rotating propeller are transmitted to a ship or submarine hull via both the propeller shaft and the pressure field that is created in the surrounding water. This pressure field has hydrodynamic and acoustic components, because water is a compressible medium with a finite speed of sound. The work described in this paper is a pilot study to investigate the combination of forces generated by the propeller motion that are transmitted to a submerged body. Fluctuating propeller forces are transmitted along the Shafting System to result in structural excitation of the submarine hull. These forces are also transmitted to the surrounding fluid and result in an external hull pressure field, because they correspond to acoustic dipoles. Both types of hull excitation contribute to hull vibration and underwater radiated noise. In order to demonstrate the fundamental nature of the problem, the case of a propeller located on the principal axis of a finite cylinder is considered, which represents a typical submarine arrangement. The analysis in this work has been simplified by considering only stationary fluctuating forces at the propeller hub and by regarding the propeller, hull and shaft as rigid structures. The relative magnitudes and phases of forces transmitted by the fluid and propeller shaft change with frequency in the range containing both low multiples of propeller blade passing frequency and broadband random components due to turbulent flow in the submarine wake. The effects of a finite speed of sound are found to be significant at low frequencies, causing changes in the hull forces that would be computed by assuming that water is incompressible. Results are presented describing the properties of acoustic dipole sources, which have both hydrodynamic and acoustic pressure fields that change in relative importance with distance from the source.

Ying Chen - One of the best experts on this subject based on the ideXlab platform.

  • Longitudinal vibration of marine propeller-Shafting System induced by inflow turbulence
    Journal of Fluids and Structures, 2017
    Co-Authors: Ying Chen, L.-c. Wang, H. X. Hua
    Abstract:

    The multi-modal vibration characteristics of a ten-bladed marine propeller and its Shafting System induced by the inflow turbulence are numerically investigated. Firstly, the distributed pressure on the propeller face is computed by the correlation method according to the statistical characteristics of isotropic turbulence. Next, the mapped unsteady pressure is applied on the blades and the associated random vibration responses of the immersed elastic propeller and its Shafting System are computed by using the modal superposition method. Finally, vibration characteristics of the propeller and its unsteady thrust transmitted to the foundation are analyzed with different dynamic parameters of the System. The results show that amplification of the unsteady thrust associated with the low-order bending modes of the propeller blades cannot be neglected, especially when the frequency of the first bending mode approaches that of the longitudinal vibration mode of the Shafting System. The propeller with ‘soft’ blades suffers higher excitation intensity at its first natural frequency but the corresponding modal hydrodynamic damping may be enhanced.

Faculty Of Engineering - One of the best experts on this subject based on the ideXlab platform.

  • Structural and acoustic responses of a submerged hull
    University of New South Wales. Mechanical & Manufacturing Engineering, 2016
    Co-Authors: Mechanical Manufacturing & Engineering, Faculty Of Engineering
    Abstract:

    Underwater radiated sound from marine vessels is a significant problem for research, fishing and military vessels,and is a major source of pollution in the marine environment. Vibrational modes of a marine vessel are excited byforces from the propeller that are transmitted via the propeller-Shafting System, resulting in subsequent soundradiation. Structural forces arising from on-board machinery also excites the vessel and contributes to structure-bornesound. The aim of this thesis is to characterize the vibro-acoustic responses of a submerged pressure hullunder external harmonic force excitation from the propeller-Shafting System and internal excitation due to on-boardmachinery. The pressure hull is simplified as a fluid-loaded cylindrical shell. Both deterministic and statistical modelsare developed. At low frequencies, the structure is modelled using finite elements while the surrounding water ismodelled using boundary elements. At higher frequencies, a hybrid finite element/statistical energy analysis(FE/SEA) method is implemented, in which a block mass to simulate on-board machinery is modelled as adeterministic subSystem with low modal density, while the cylindrical shell and an internal plate on which the rigidmass is mounted are modelled as statistical subSystems with high modal density. A hybrid FE/SEA model of nestedcylindrical shells is also developed. Annular ribs are used to link the inner and outer shells. To examine the effects ofmass distribution along the length of the submerged pressure hull, a semi-analytical model of a fluid-loaded cylindrical shell comprising a linear array of evenly distributed dipole sources is presented. The radiated sound of aneutrally buoyant cylinder with uniform and non-uniform stepwise mass distribution in the longitudinal direction of thecylinder is then investigated. The effect of non-uniform mass distribution on peak sound power of the first few cylinderbending modes is described. Finally, experiments have been conducted to measure the natural frequencies andmode shapes of a scaled coupled cylinder/plate structure in air. A freely-suspended open cylindrical shell with aninternal rectangular plate longitudinally connected to the shell via brackets is considered

  • Numerical predictions of the radiated sound power from submerged shells
    University of New South Wales. Mechanical & Manufacturing Engineering, 2013
    Co-Authors: Mechanical Manufacturing & Engineering, Faculty Of Engineering
    Abstract:

    Sound radiation from marine vessels at low frequencies is of great significance for the civilian and military naval industries. The marine vessel is excited by structural forces from the propeller that are transmitted via the propeller Shafting System as well as via the fluid path. Further sources of excitation are the internal machinery and other external sound sources such as hull flow noise. This thesis develops numerical models to predict the radiated sound power of a fully submerged submarine model at low frequencies, where the wavelength of underwater sound is more than about one third of the hull length. The pressure hull, which is designed to withstand deep diving pressure and accommodates the crew, machinery and weapon Systems, is the main component of a submarine for the consideration of low frequency radiated sound.The aim of this thesis is to characterize the acoustic responses of a fully submerged pressure hull under harmonic forcing functions. The pressure hull is simplified as a cylindrical shell with hemispherical end closures. The structure is modelled using finite elements while the surrounding water is modelled using boundary elements. The simultaneous solution of both models is achieved by means of two-way coupling. A novel coupling algorithm that accounts for the curvature of finite and boundary elements using quadratic shape functions is developed and validated. The fully coupled finite element/boundary element model is solved for structural displacement and sound pressure on the wetted surface. This primary solution is used to derive the far-field radiated sound pressure field and the total radiated sound power. The size of the numerical model is reduced significantly by projecting the structural finite element matrices onto a Krylov subspace. The reduced order finite element model is coupled with the unmodified acoustic boundary element model and solved directly by Gaussian elimination. Results from the numerical models developed in this thesis are compared with those from analytical models of a fluid-loaded sphere and a fluid-loaded cylindrical shell with flat end plates. Excellent agreement between the results of the numerical and analytical models is observed. The fully coupled System of equations of the vibro-acoustic model is transformed into an algebraic nonlinear eigenvalue problem. The solution of the eigenvalue problem yields the fluid-loaded structural modes of the submerged structure. The fluid-loaded structural modes are used to derive the modal contributions to the sound pressure field and the radiated sound power. The modal contribution technique is applied to a fluid-loaded spherical shell with and without an internal structure, and a fluid-loaded cylindrical shell with hemispherical end caps. For the cylinder, it is shown that the contributions from the circumferential breathing and bending shell modes dominate the acoustic responses at low frequencies for excitation acting on one end of the cylinder. The fully coupled finite element/boundary element model is applied to study the effects of mass distribution, buoyancy and internal mass isolation on the low frequency acoustic responses of the pressure hull model. Sound radiation of a rigid cylindrical shell is considered initially. The rigid body analysis yields asymptotic limits that apply to any fluid-loaded structure at low frequencies. It is shown that positive buoyancy of submerged hulls causes an increase in the radiated sound power in the frequency range considered. Internal components of a submarine are mounted in such a way to withstand shock loading and to attenuate the transmission of vibration. For external excitation directly acting on the pressure hull, it is shown that flexibly mounted masses effectively disappear at frequencies above about twice the chosen mounting frequency, which results in positive overall buoyancy of the vessel. For flexibly mounted machinery rafts, it is shown how the raft dynamics and the distribution of mounts influence the radiation due to either propeller or machinery forces

  • Passive and active control of the sound radiated by a submerged vessel due to propeller forces
    University of New South Wales. Mechanical & Manufacturing Engineering, 2010
    Co-Authors: Mechanical Manufacturing & Engineering, Faculty Of Engineering
    Abstract:

    An important cause of sound radiation from a submarine in the low frequency range is fluctuating forces at the propeller. The forces arise from the operation of the propeller in a non-uniform wake and are transmitted from the propeller to the submarine hull through both the shaft and the fluid. The sound radiated from the submarine is due to the combination of sound radiation caused by hull and propeller vibrations as well as dipole sound radiation from the propeller. To improve the stealth of a submarine, the radiated sound power can be reduced using passive and active noise and vibration control mechanisms. In this thesis, dynamic models of a submarine hull and propeller/Shafting System are developed. To reduce the radiated sound fields, passive control is introduced using a hydraulic vibration attenuation device known as a resonance changer, which is implemented in the propeller/Shafting System. Active control techniques are implemented using either tuned actuators or a control moment.To initially obtain the structural and acoustic responses of a submarine hull, an analytical model and fully coupled finite element/boundary element model are developed, for a simplified physical model of the hull. The submerged body under axial excitation is modelled as a ring-stiffened cylindrical shell with finite rigid end closures and separated by bulkheads into a number of compartments. Lumped masses are located at each end to maintain a condition of neutral buoyancy. In the low frequency range, only the axial hull modes in accordion motion and axial vibration of the propeller/Shafting System are examined, which gives rise to an axisymmetric case. The frequency responses, axial and radial responses of the cylinder and the radiated sound pressure from both the analytical and computational models are compared. A dynamic model of the propeller/Shafting System developed computationally and including the resonance changer is then coupled to the FE/BE model of the hull which is subject to both structural excitation from the propeller/Shafting System and acoustic excitation from the propeller. The influence of tailcone properties on the structural and acoustic responses of the submarine are investigated.Passive control is implemented to attenuate the hull responses using a resonance changer. It is demonstrated that the performance of the resonance changer is negatively influenced at frequencies above the fundamental axial resonance of the hull by the effect of forces transmitted through the fluid. When the resonance changer is optimised to minimise excitation of the hull via the propeller shaft, the increased axial movement of the propeller results in an additional sound field that excites the submarine hull in a similar manner to the fluid forces that arise directly from the hydrodynamic mechanism. Cost functions that represent the submarine radiated sound power are developed, where the virtual stiffness, damping and mass of the resonance changer were chosen as design parameters. The minima of the cost functions are found by applying gradient based optimisation techniques. The adjoint operator is employed to calculate the sensitivity of the cost function to the design parameters. The influence of sound radiation due to propeller vibration on the optimisation of the resonance changer is investigated. The influence of the reduction in amplitude for higher harmonics of the blade passing frequency on the control performance is also examined.Different active control strategies are investigated, in which active control is applied to the propeller/Shafting System and/or to the submarine hull. Active vibration control and discrete structural acoustic sensing based on the far field radiated sound power were considered in the development of the cost functions. In addition, the performance of a of a combined passive and active control System is investigated. Significant reduction of radiated sound power is achieved when an active control System using tuned actuators is combined with a resonance changer. The structural responses of a model scale, free flooded submarine tailcone are investigated computationally and experimentally. The tailcone is represented by a thin-walled conical shell attached to a stiff plate. The stiff plate represents the pressure hull end plate of the submarine and is subject to axial excitation correlated to propeller forces. Good agreement between the computational and experimental results are found for the tailcone in air as well as for the submerged tailcone

  • Optimum resonance changer for submerged vessel signature reduction.
    2007
    Co-Authors: Paul Griffin, Mechanical Engineering, Faculty Of Engineering
    Abstract:

    In maritime vessels, it is desirable to minimise the structural and acoustic responses for several reasons, including passenger comfort, minimisation of crew fatigue, and in the case of military vessels, to avoid detection. The propeller-Shafting System represents one of the most critical areas which must be addressed in order to reduce the low frequency acoustic signature. The propeller-Shafting System is primarily excited by axial oscillations at the propeller. The force transmitted along the propeller-Shafting System from these disturbances results in axial excitation of the hull and subsequent sound radiation. The aim of this thesis is to apply a combination of passive and active control techniques, in order to minimise the low frequency radiated noise signature of a pressure hull submerged in a fluid.Dynamic models of the propeller-Shafting System, foundation and cylindrical hull including complicating factors such as fluid loading, bulkheads and onboard equipment are developed and described using the transmission matrix approach. This modular description enables greater flexibility for dynamic modelling of the propeller Shafting System, and can be easily manipulated for future design modifications. The far-field radiated sound pressure from the submarine hull is evaluated and related to the force delivered to the hull by the propeller-Shafting System. A passive optimisation scheme involving a genetic and general non-linear constrained algorithm is used to minimise fitness functions associated with the vibration of the propeller, vibration transmission to the hull and far-field radiated sound pressure over a low frequency range. This results in optimal resonance changer parameters for single and multiple resonance changers in a variety of configurations.A new quasi-adaptive resonance changer System is proposed and optimised to minimise the radiated sound pressure or propeller velocity. The optimal use of an adaptive resonance changer is investigated in both the frequency and time domains to reduce the hull velocity and subsequently the far-field radiated sound pressure. Fully active control is also evaluated by introducing a control force to the resonance changer with the aim of minimising either the propeller velocity or the radiated noise level. Finally, the concept of hybrid control is investigated by coupling passive, active and semi-active control techniques together to improve the overall performance