Cavity acoustic tones suppression

A cavity system for suppressing resonance and/or acoustic tones comprises a cavity 2 and a spoiler 204. The spoiler comprises front and rear surfaces. The cavity has a leading edge 14 relative to an actual or intended flow direction 3 of a fluid over the cavity. The spoiler is positioned in proximity to this leading edge with its longitudinal axis 1 perpendicular to or at an oblique angle to the actual or intended flow direction such that the front surface faces towards the flow direction. A first region of the spoiler extends further towards the leading edge than a second region of the spoiler. In use, the cavity system prevents vortices and/or noise being generated in cavities, especially those found on aircraft such as payload and/or weapon bays and landing gear bays.