A method of reducing engine induced aircraft cabin resonance in an aircraft, the method comprising the steps of: sensing a parameter representative of current aircraft altitude and speed; sensing a parameter representative of current engine operating conditions of a first turbofan gas turbine engine and of a second turbofan gas turbine engine; and in a control system: processing the parameter representative of current aircraft altitude and speed and the parameter representative of current engine operating conditions to supply a core engine speed difference (ΔN2) value; processing the parameter representative of current aircraft flight conditions and the parameter representative of current engine operating conditions to supply a variable inlet guide vane (VIGV) sensitivity value, the VIGV sensitivity value representative of a change in core engine speed with a change in VIGV position at the current aircraft flight conditions; processing the ΔN2 value and the VIGV sensitivity value to determine a variable inlet guide vane (VIGV) offset value; and applying the VIGV offset value to a VIGV reference command associated with one of the first or second turbofan gas turbine engine, to thereby cause the VIGVs of one of the first or second turbofan gas turbine engine to move to a more closed position. sensing a parameter representative of current aircraft altitude and speed; sensing a parameter representative of current engine operating conditions of a first turbofan gas turbine engine and of a second turbofan gas turbine engine; and in a control system: processing the parameter representative of current aircraft altitude and speed and the parameter representative of current engine operating conditions to supply a core engine speed difference (ΔN2) value; processing the parameter representative of current aircraft flight conditions and the parameter representative of current engine operating conditions to supply a variable inlet guide vane (VIGV) sensitivity value, the VIGV sensitivity value representative of a change in core engine speed with a change in VIGV position at the current aircraft flight conditions; processing the ΔN2 value and the VIGV sensitivity value to determine a variable inlet guide vane (VIGV) offset value; and applying the VIGV offset value to a VIGV reference command associated with one of the first or second turbofan gas turbine engine, to thereby cause the VIGVs of one of the first or second turbofan gas turbine engine to move to a more closed position. processing the parameter representative of current aircraft altitude and speed and the parameter representative of current engine operating conditions to supply a core engine speed difference (ΔN2) value; processing the parameter representative of current aircraft flight conditions and the parameter representative of current engine operating conditions to supply a variable inlet guide vane (VIGV) sensitivity value, the VIGV sensitivity value representative of a change in core engine speed with a change in VIGV position at the current aircraft flight conditions; processing the ΔN2 value and the VIGV sensitivity value to determine a variable inlet guide vane (VIGV) offset value; and applying the VIGV offset value to a VIGV reference command associated with one of the first or second turbofan gas turbine engine, to thereby cause the VIGVs of one of the first or second turbofan gas turbine engine to move to a more closed position.