The speech reception threshold can be estimated using EEG electrodes in and around the ear

Objective.Previous studies have demonstrated that the speech reception threshold (SRT) can be estimated using scalp electroencephalography (EEG), referred to as SRT_neuro. The present study assesses the feasibility of using ear-EEG, which allows for discreet measurement of neural activity from in and around the ear, to estimate the SRT_neuro.Approach.Twenty young normal-hearing participants listened to audiobook excerpts at varying signal-to-noise ratios (SNRs) whilst wearing a 66-channel EEG cap and 12 ear-EEG electrodes. A linear decoder was trained on different electrode configurations to estimate the envelope of the audio excerpts from the EEG recordings. The reconstruction accuracy was determined by calculating the Pearson's correlation between the actual and the estimated envelope. A sigmoid function was then fitted to the reconstruction-accuracy-vs-SNR data points, with the midpoint of the sigmoid serving as the SRT_neuroestimate for each participant.Main results.Using only in-ear electrodes, the estimated SRT_neurowas within 3 dB of the behaviorally measured SRT (SRT_beh) for 6 out of 20 participants (30%). With electrodes placed both in and around the ear, the SRT_neurowas within 3 dB of the SRT_behfor 19 out of 20 participants (95%) and thus on par with the reference estimate obtained from full-scalp EEG. Using only electrodes in and around the ear from the right side of the head, the SRT_neuroremained within 3 dB of the SRT_behfor 19 out of 20 participants.Significance.These findings suggest that the SRT_neurocan be reliably estimated using ear-EEG, especially when combining in-ear electrodes and around-the-ear electrodes. Such an estimate can be highly useful e.g. for continuously adjusting noise-reduction algorithms in hearing aids or for logging the SRT in the user's natural environment.