## 5 Conclusions  
This study aimed to assess the effect of noise and face masks on speech intelligibility in bilateral hard-of-hearing young listeners, equipped either with bilateral cochlear implants or with a monolateral cochlear implant and contralateral hearing aid. Twenty participants were recruited voluntarily, who were clustered into an experimental group of 14 hard-of-hearing children and a control group of six children with typical hearing. A specific listening test was built according to the requirements of this project, i.e., to assess speech intelligibility and listening difficulty under different noise conditions, accounting for the presence of different types of face masks. The participants were able to carry out the test remotely using a computer and an internet network. Since the involved participants were all in the age range between 7 and 15 years of age, their parents' consent and presence during the execution of the listening tests was required. This strategy allowed researchers to overcome the limitations imposed by the pandemic rules and therefore to collect data without the possibility of performing the test in the presence of the researchers. Two main outcomes were found within this study. First, concerning the effect of different SNRs on speech intelligibility, the presence of noise at all levels significantly degraded speech intelligibility and also prompted higher (worse) listening difficulty. Considering SNRs of +10 dB, +5 dB, and 0 dB, a drop in speech intelligibility from an average of 90% to 85% to 60%, respectively, was found for hard-of-hearing listeners. Listeners with typical hearing, instead, exhibited a reduced drop in speech intelligibility at the three SNRs that consisted of 95% to 90% to 85%. From a practical point of view, until an SNR as low as +5 dB, it was found that speech intelligibility was higher than 75% for hard-of-hearing listeners. This is a satisfactory value that can still be acceptable within a classroom. Therefore, a possible strategy to support the design of classrooms to make them adequate for several listeners, e.g., young children with cochlear implants or hearing impairment in general, can be to emphasize this aspect at an early stage. Second, concerning the effect of different types of face masks on speech intelligibility, data confirmed that they play a crucial role in the speech communication process. The no-mask condition proved to be the one with higher speech intelligibility values, as expected. For children with hard-of-hearing listeners, using Masks 1 and 2, lower speech intelligibility values were obtained and a corresponding higher listening difficulty was shown. Conversely, Mask 3 provided speech intelligibility and listening difficulty values that were comparable to the no-mask condition. It had the least impact on speech comprehension and, therefore, this could be considered to be the most suitable for the teacher to wear. In summary, due to the main difference in the intrinsic characteristics of face masks with respect to their acoustic properties, the use of masks with lower sound absorption and transmission loss is worthwhile in those contexts where the speech communication process is of primary importance, and where vulnerable subjects, such as hard-of-hearing children, are present. [PERSON] and [PERSON] conceptualized the research; [PERSON], [PERSON] and [PERSON] selected, invited, and involved the participants; [PERSON] conducted acoustic characterization measurements of the face masks; [PERSON] and [PERSON] performed the listening tests; [PERSON], [PERSON], [PERSON] and [PERSON] organized the database and performed the statistical data analysis; [PERSON] wrote the first draft of the manuscript; all the authors reviewed the article drafts; [PERSON] supervised the research activity. All authors have read and agreed to the published version of the manuscript. This research was sponsored by the C.I.A.O Ci Sentiamo ONLUS.