A technique was developed for the inference of shutdown reactivity by using the experimental auto - or cross-power spectral density data normally obtained in neutron noise experiments at low and intermediate frequencies (Low-Intermediate Frequency Technique, LIFT). Reactivity determined by LIFT is dependent on the neutron detection efficiency, whereas reactivity determined by normal noise experiments is dependent on the neutron generation time. Furthermore, if a noise experiment is to be used for the inference of reactivity, very little additional experimental data are required for the application of LIFT. It is recommended that LIFT be applied as a complementary measurement to the normal noise measurement. Results determined by LIFT for the shutdown state for previously reported one- and two-detector noise experiments agree well with results determined by normal noise methods.