Speech-evoked ABR Speech-in-noise Brainstem encoding

both optimal and challenging listening conditions has not yet been systematically documented. This evoked ABR from one test to another is small (Edwards et al., 1982; Oyler et al., 1991). Thus, temporal precision of the response is such that even subtle divergences in peak latencies on the order of frac-tions of milliseconds are clinically significant. More recently, the ABR has been used to evaluate underlying central processes involved in encoding more complex signals pre-sponds to the periodicity of the vowel (Boston and Møller, 1985; Akhoun et al., 2008; Johnson et al., 2008a; Hornickel et al., 2009b). Although the morphology of the onset response of the speech-evoked ABR is similar to that elicited by clicks (Song et al., 2006), the FFR does not appear in the transient click-evoked response. The FFR faithfully reflects the encoding of the funda-mental frequency and harmonic structure of the speech stimulus (Moushegian et al., 1973). Thus, an advantage of the speech-evoked ABR is that it reflects both transient and sustained portions of the stimulus which can be objectively assessed at the level of the brainstem