The present disclosure relates to a blade noise reduction apparatus arranged at a trailing edge of a blade and reducing noise during rotation of the blade. The blade noise reduction apparatus includes an attachment unit combined with the trailing edge of the blade, and a sawtooth unit formed to protrude in a longitudinal direction of the attachment unit from the attachment unit, wherein the sawtooth unit includes a lower sawtooth unit including first sawteeth repeatedly arranged thereon, and an upper sawtooth unit including a second sawtooth having a length less than a length of the first sawtooth and arranged on an upper surface of each first sawtooth.

A wind turbine noise suppression system can include a sound absorbing batting and a fabric sheet within a column of the wind turbine. The sheet can hang within the column whereas the batting can be placed in at least a bottom and top region. A vibration isolation pad at the top of the column can mitigate a megaphone effect. The pad can be combined with an isolation washer. The pad can be less than a half inch thick, whereas the isolation washer can be less than a quarter inch thick. A sound curtain can be installed at a base of the column to suppress bell resonance. The system can, for example, reduce wind turbine noise up to ninety percent.

An acoustic core may include an array of resonant cells configured as a plurality of resonant cell groups. The resonant cell groups may include a plurality of resonant cells configured as a partitioned resonant cell that include a converging resonant cell and a diverging resonant cell. The converging resonant cell and the diverging resonant cell may be defined by a plurality of cell walls integrally formed with one another and a partition integrally formed with the plurality of cell walls. The partition may at least partially delimit the converging resonant cell from the diverging resonant cell. The converging resonant cell may define an upper resonant space delimited by the partition and a top face of the array of resonant cells. The diverging resonant cell may define a lower resonant space delimited by the partition and a bottom face of the array of resonant cells.

A compressor includes: a case, a compression unit that is provided inside the case and that includes a cylinder and a piston configured to reciprocate inside the cylinder to compress refrigerant, a driving unit that includes a stator disposed inside the case and a plurality of permanent magnets configured to reciprocate with respect to the stator and that is configured to provide a driving force to the compression unit, and a resonator that is configured to reduce noises generated while the compression unit is operated, that is disposed between the compression unit and an inner surface of the case facing the compression unit in an axial direction, and that is spaced apart from the compression unit.

The present invention relates to a method of controlling a wind turbine comprising a tower supporting a rotor comprising a plurality of pitch-adjustable rotor blades. The method includes obtaining a movement signal indicative of a lateral movement of the tower; determining a pitch modulation signal, based on the movement signal, for actuating a rotor blade to produce a desired horizontal force component to counteract the lateral movement of the tower; determining a radial force component acting on a rotor blade; determining a phase offset parameter for the rotor blade based on the radial force component; and, transforming the pitch modulation signal into a pitch reference offset signal for the rotor blade based on the phase offset parameter.

A rotor blade with a leading edge and a trailing edge is provided, wherein the rotor blade is for being exposed to a fluid flowing substantially from the leading edge to the trailing edge, the rotor blade includes at least three sensors designed for detecting flow characteristics of the fluid and providing respective sensor signals, wherein the sensors are arranged with a non-uniform spacing, and the rotor blade further includes at least one actuator for producing an anti-noise signal based on a sensor signal, the sensors and the actuator are arranged at the surface of the rotor blade, and the actuator is arranged and prepared such that flow-induced edge noise of the rotor blade, which is generated by the fluid, is at least partly cancelled out by the anti-noise signal. A method for creating such rotor blade and a related wind turbine is also provided.

A rotor blade with a leading edge and a trailing edge, wherein the rotor blade is designed and configured for being exposed to a fluid flowing substantially from the leading edge to the trailing edge) of the rotor blade, the rotor blade includes at least one sensor for detecting flow characteristics of the fluid, and the rotor blade further includes at least one actuator for producing an anti-noise signal. The sensor and the actuator are both arranged at the surface of the rotor blade, and the actuator is arranged and prepared such that flow-induced edge noise of the rotor blade, which is generated by the fluid, is at least partly cancelled out by the anti-noise signal. The disclosure furthermore relates to a wind turbine including at least one such rotor blade.

A method of identifying an operating parameter of a wind turbine that contributes to the generation of tonal noise. The method comprises acquiring operating parameter data associated with a plurality of operating parameters of the wind turbine. The operating parameter data comprises a set of values for each operating parameter of the wind turbine. Noise data is also acquired that includes tonal noise produced by the wind turbine and is synchronised with the operating parameter data. The noise data is then binned with respect to a set of operating parameter values of a first operating parameter, and, for each of one or more of the bins, the noise data in the bin is analysed with respect to a set of values of a second operating parameter. The method then determines if there is a relationship between the second operating parameter and tonal noise produced by the wind turbine based on the analysis.

The present invention relates to airfoils having surface treatments to reduce trailing edge noise. The surface treatment is designed to reduce trailing edge noise by modifying the boundary layer turbulence as it approaches the trailing edge. The surface treatment accomplishes its function by breaking up spanwise-oriented turbulence approaching the trailing edge, thereby reducing the spanwise correlation lengthscales; deflecting the boundary layer turbulence away from the edge; and/or creating spanwise vortices or instability waves to reduce the turbulence-edge interaction.

A method of masking wind turbine noise from a wind turbine. Masking noise is generated to produce resultant noise with a modulation depth which is less than a modulation depth of the wind turbine noise and an average level which is greater than an average level of the wind turbine noise. The masking noise is either un-modulated masking noise with a substantially constant level, or amplitude-modulated masking noise which is phase-shifted relative to the wind turbine noise and has a modulation depth which is less than the modulation depth of the wind turbine noise.