Predicting speech reception thresholds of cochlear implant users using a modified envelope based measure

An envelope-correlation based measure (ECM), proposed in Yousefian and Loizou (2012), was applied to predict the speech reception thresholds (SRTs) of nine pre- and post-lingual cochlear implant (CI) users in the presence of speech-shaped masker and a female competing talker. A principal component analysis showed that CI users' aided pure-tone thresholds were almost orthogonal to the predictions made by ECM, indicating that the ECM does not take aided hearing loss into account. A modified ECM is proposed which includes pure-tone thresholds into the predictions. The proposed model adjusts the ECM predictions based on the pure tone threshold values, and is able to predict CI users' SRTs with higher correlation (r=0.92) compared to the original ECM (r=0.59). The results reported in this study indicate that information available on MAPs (e.g. T-levels, number of active electrodes) may not be sufficient to predict CI users' SRTs in noise. In additions, results show that lack of audibility (i.e. elevated pure-tone thresholds) can dramatically limit speech intelligibility in noise in (even experienced) CI users.