APA Dictionary of Psychology

a formula describing the ability to follow changes in the magnitude of a stimulus over time. In psychoacoustics, a TMTF is usually obtained by measuring the amount of sinusoidal amplitude modulation that is necessary to detect the modulation (a modulation threshold) as a function of the frequency of that modulation. TMTFs are similarly measured in other modalities. The utility of the TMTF is grounded in linear systems theory, specifically the principle that the transfer function of a linear system provides a complete description of the system.