An auxiliary power unit for an aircraft includes a turbine engine. An inlet includes an opening and a passageway between the opening and the turbine engine. An acoustic splitter is supported within the passageway for attenuating noise within the inlet. An inlet door is movable between a closed position and a fully open position. A portion of the inlet door aligns with a part of the passageway in at least a first position and divides the passageway to deflect ice and noise in at least a second position. An air inlet and a method are also disclosed.