1. A method for warning a machine operator of a manned machine system that an emergency is imminent, comprising: determining, by a processor of a safety warning system of the manned machine system, whether a machine condition is at or below a potential emergency threshold; determining, by the processor of the safety warning system, whether a target action of the manned machine system is performed by the machine operator in response to determining that the machine condition is at or below the potential emergency threshold; outputting, by the safety warning system, a masked priming audio stimulus associated with the target action of the manned machine system in response to determining that the target action of the manned machine system is performed by the machine operator while the machine condition is at or below the potential emergency threshold, wherein the masked priming audio stimulus is injected into an audible audio stream output in the manned machine system; determining, by the processor of the safety warning system, whether the machine condition is above the potential emergency threshold; outputting, by the safety warning system, the masked priming audio stimulus associated with the target action of the manned machine system in response to determining that the machine condition is above the potential emergency threshold; determining, by the processor of the safety warning system, whether the machine condition is at or above an emergency threshold; and outputting, by the safety warning system, an overt danger audio warning associated with the emergency in response to determining that the machine condition is at or above the emergency threshold.