US Patent 10487744 Fence for duct tone mitigation

Aspects of the disclosure are directed to a system associated with an engine of an aircraft comprising: a duct, an inlet coupled to the duct, and a fence coupled to the inlet or located upstream of the inlet. In some embodiments, the system further comprises a valve body coupled to the duct. In some embodiments, the valve body includes at least one valve that is configured to rotate between a closed state and an open state.