## 4 Discussion
However, they did not perform any acoustic measurements of the masks used in the study, so specific conclusions regarding the acoustic effects of these masks could not be determined and a perfect comparison with this study is not possible. This study shows that, on average, speech intelligibility decreases for HoH and TH listeners in the presence of Masks 1 2. Mask 1 was characterized by a higher sound absorption and attenuation. Masks 2 and 3 were similar in terms of sound absorption and attenuation; however, the latter was significantly higher for Mask 2, at 2.5 kHz. In a very recent study, [PERSON] et al. [36] showed that an increased sound attenuation at around 2 kHz may decrease the second formant of speech, with the main negative consequence being the reduction of vowel discrimination. Therefore, such an effect could explain the difference in intelligibility scores between Masks 2 and 3. Overall, the result was also corroborated due to statistical analyses, which were based on the search for the probability of correctly recognizing a word (PCR). Similarly, listening difficulty was higher for the higher competitive acoustic characteristics of face masks. As a general consideration, possible solutions to account for all the premises at the same time, i.e., the need to improve speech intelligibility towards HoH children under realistic acoustic scenarios and the need to reduce the spread of COVID-19 infection, are needed. So far, studies have proposed the use of face shields and see-through prototype masks, as they are effective in allowing for lip-reading [22; 34]. However, they are not easy to find and are not commonly used in everyday practice. This study is thus a step forward to acknowledging the importance of accounting for the combined effect of personal behavior (e.g., wearing face masks to protect society) together with environmental modifications to support the speech communication process. Indeed, increasing SNR in the environment is an effective strategy to increase speech intelligibility. Although this objective can be reached because of the setting of the cochlear implant, it is also a design challenge for researchers and professionals in acoustics, who should guarantee an adequate acoustic environment where everyday activities take place. Therefore, the control of reverberation and noise is essential. The presented study fills in gaps in the available literature [35] (i) it is based on speech and noise stimuli that were recorded under controlled acoustic conditions and therefore are highly repeatable; (ii) the laboratory characterization of the face masks was based on well-defined standards and procedures; (iii) the presentation of the listening tests was performed to two ears at the same time, so binaural hearing cues were accounted for as in ecological listening situations; (iv) a comparison between the EG of HoH listeners and the CG with TH ones could be performed to obtain results that have larger applicability in everyday life situations. However, some limitations are still present, and the main ones can be summarized as follows. First, a small number of participants was achieved. The main obstacle to involving a wider group of HoH listeners was related to the restrictions due to the COVID-19 pandemic, which also included the fact that the experimenters only met the listeners and their families remotely, so little mutual knowledge was possible. Second, the great variability in HoH treatment did not allow for the inclusion of a greater number of participants with similar characteristics. Third, it would be useful to investigate the learning effect on speech perception, thus on speech intelligibility, for HoH and TH listeners.