Calculated engine core noise levels, based on NASA-Lewis prediction procedures, for five representative helicopter engines are compared with measured total helicopter noise levels and proposed FAA helicopter noise certification requirements. Comparisons are made for approach, level flyover, and takeoff procedures. The measured noise levels are generally significantly greater than those calculated for the core noise levels, except for the Sokorsky S-61 helicopter using two General Electric T-58 engines. However, the calculated engine core noise levels are generally at or within 3 dB of the proposed FAA noise rules. Consequently, helicopter engine core noise can be a significant contributor to the overall helicopter noise signature and, in all cases, will provide a floor to a further decrease in future noise regulations.