Unhindered auditory and visual signals are essential for a sufficient speech understanding of cochlear implant (CI) users. Face masks are an important hygiene measurement against the COVID-19 virus but disrupt these signals. This study determinates the extent and the mechanisms of speech intelligibility alteration in CI users caused by different face masks. The audiovisual German matrix sentence test was used to determine speech reception thresholds (SRT) in noise in different conditions (audiovisual, audio-only, speechreading and masked audiovisual using two different face masks). Thirty-seven CI users and ten normal-hearing listeners (NH) were included. CI users showed a reduction in speech reception threshold of 5.0 dB due to surgical mask and 6.5 dB due to FFP2 mask compared to the audiovisual condition without mask. The greater proportion of reduction in SRT by mask could be accounted for by the loss of the visual signal (up to 4.5 dB). The effect of each mask was significantly larger in CI users who exclusively hear with their CI (surgical: 7.8 dB, p = 0.005 and FFP2: 8.7 dB, p = 0.01) compared to NH (surgical: 3.8 dB and FFP2: 5.1 dB). This study confirms that CI users who exclusively rely on their CI for hearing are particularly susceptible. Therefore, visual signals should be made accessible for communication whenever possible, especially when communicating with CI users.
Keywords: hearing; personal protective equipment; speech intelligibility; speech reception threshold test; speechreading.