Psychoacoustic forward masking can probe the efferent reflex without its own contamination.

Evidence

The advantage of psychoacoustical methods to infer the efferent effect is that they can be used in cases of both normal and mildly impaired hearing (unlike OAEs which can be eliminated by a mild hearing loss). … The FDMC method avoids the confounds of previous forward-masking methods used to measure the efferent effect by using a combined duration of the masker-plus-signal stimulus of 25 ms, which is within the efferent onset delay. Hence, the representation of the signal should be unaffected by efferent activity elicited by the masker. The effect of efferent activation on cochlear gain can then be separately studied by presenting a precursor sound (to activate the efferent system) prior to the onset of the combined FDMC masker-signal stimulus. — Dijk, Pim van, Physiology, Psychoacoustics and…, 5956

Categorization

• DEFINE: Explains the FDMC method’s design logic: exploiting the 25-40 ms efferent delay as a measurement window.