The helicopter pilot reported that he was being evaluated for a pilot position with a perspective employer, who was an airplane pilot-rated passenger and occupied the right front seat. He was asked to perform an autorotation as part of the evaluation, and while entering the autorotation, he noticed that the rotor and engine needles were split and that the engine tachometer indicated 0 rpm. He believed that the engine had failed. The pilot maintained the rotor rpm in the green and entered a flare about 40 ft above ground level. He attempted to cushion the landing, but the helicopter landed hard. The pilot reported that he could not hear if the engine was running during the flight because he was wearing a noise-canceling headset.