When trains of short, tone burst stimuli are presented to a test subject, the individual ABRs generated in response to the stimulus train merge together into a steady state wave called a envelope following response (EFR). If the stimulus train consists of broadband clicks, the steady-state evoked response is called a rate following response, or RFR (Supin et al. 2001). The magnitude of these following responses can be plotted as a function of the pulse presentation rate to generate a Modulation Rate Transfer Function, (MRTF) when the stimulus is a sinusoidally amplitude modulated (SAM) tone. When the stimulus is a broadband click, these functions have been termed an RFR amplitude-vs-rate curve (Supin et al. 2001). In mammals, including marine mammals, these functions are generally the shape of a low-pass filter, with response magnitudes decreasing and eventually ceasing above a certain modulation or presentation rate as the auditory system can no longer follow the rapid changes of the stimulus envelope. The upper limits of resentation rates that elicit ABR responses have been used as an estimation of the temporal resolution of test subjects (Supin and Popov 1995; Popov and Supin 1998; Linnenschmidt et al. 2013).
(taken from Smith et al 2018)