A hydraulic damping apparatus 2 comprising a conduit 4 for a hydraulic fluid having a port 12 in a wall of the conduit 4; a resonator 6 having a chamber 9 and a neck 10, the neck 10 being arranged to provide fluid communication between the chamber 9 and the port 12. The apparatus 2 further comprises a first pressure sensor 22 arranged to sense pressure in the conduit 4 upstream of the port 12, a second pressure sensor 24 arranged to sense pressure in the conduit 4 downstream of the port 12, and a controller 18 configured to determine the amplitude of a pressure fluctuation sensed by the first pressure sensor 22 and the amplitude of a pressure fluctuation sensed by the second pressure sensor 24. The controller 18 is further configured to vary a resonant frequency of the resonator 6 in accordance with a difference between the amplitude of the pressure fluctuation sensed by the first pressure sensor 22 and the amplitude of the pressure fluctuation sensed by the second pressure sensor 24.