The complementary nature of pulsed-neutron and reactor-noise techniques in the investigation of reactor dynamic parameters is illuminated by considering the response of a reactor to two types of forcing functions. One of these forcing functions is the impulse function employed in pulsed-neutron studies, while the other is derivable from the inherent randomness of the nuclear events taking place in the reactor. Both the prompt-neutron density following a burst of neutrons into a reactor system and the spectral density of the reactor noise can be expressed in terms of the prompt-neutron decay constant, α. This, in turn, is related to the ratio β/ℓ and the reactivity of the system. Either technique can be used to measure α; however, in practice, each is limited according to a ‘figure of merit’ for a given experimental situation. Measurements made on both subcritical and critical assemblies in the Critical Mass Laboratory at Hanford illustrate the complementary feature of these two techniques and their usefulness in verifying each other's experimental results.