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 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 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 spaced from the offtake location, 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 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 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 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 spaced from the offtake location, 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 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 spaced from the offtake location,