A gas turbine engine (10A; 10B; 10C) comprising: a duct extending about an axis (C L ), the duct including an outer-duct wall having an interior-duct surface circumscribing an interior of the duct and an exterior-duct surface radially outward of the interior-duct surface relative to the axis (C L ), the outer-duct wall defining an offtake opening extending from the interior-duct surface to the exterior-duct surface , the offtake opening in fluid communication between an offtake location (L1) inside the duct and outside the duct ; and a bleed air offtake assembly including: an air line in fluid communication with inside the duct via the offtake opening , the air line having a first-line end defining a line inlet proximate to the outer-duct wall and a second-line end spaced from the first-line end; a valve located outside the duct and fluidly connected to the air line via the second-line end; and a conduit having a conduit inlet in fluid communication with inside the air line at a resonance location (L2) between the first-line end and the second-line end upstream of the valve , and a conduit outlet in fluid communication with inside the duct at a relief location (L3) spaced from the offtake location (L1), characterised in that : the conduit is located inside the air line , the bleed air offtake assembly includes a tube extending from the exterior-duct surface to the resonance location (L2) inside the air line , the tube having an exterior-tube surface , the air line has an interior-line surface surrounding the exterior-tube surface , and the conduit has an annular shape circumscribed inwardly by the exterior-tube surface and outwardly by the interior-line surface . a duct extending about an axis (C L ), the duct including an outer-duct wall having an interior-duct surface circumscribing an interior of the duct and an exterior-duct surface radially outward of the interior-duct surface relative to the axis (C L ), the outer-duct wall defining an offtake opening extending from the interior-duct surface to the exterior-duct surface , the offtake opening in fluid communication between an offtake location (L1) inside the duct and outside the duct ; and a bleed air offtake assembly including: an air line in fluid communication with inside the duct via the offtake opening , the air line having a first-line end defining a line inlet proximate to the outer-duct wall and a second-line end spaced from the first-line end; a valve located outside the duct and fluidly connected to the air line via the second-line end; and a conduit having a conduit inlet in fluid communication with inside the air line at a resonance location (L2) between the first-line end and the second-line end upstream of the valve , and a conduit outlet in fluid communication with inside the duct at a relief location (L3) spaced from the offtake location (L1), an air line in fluid communication with inside the duct via the offtake opening , the air line having a first-line end defining a line inlet proximate to the outer-duct wall and a second-line end spaced from the first-line end; a valve located outside the duct and fluidly connected to the air line via the second-line end; and a conduit having a conduit inlet in fluid communication with inside the air line at a resonance location (L2) between the first-line end and the second-line end upstream of the valve , and a conduit outlet in fluid communication with inside the duct at a relief location (L3) spaced from the offtake location (L1), <EOS>