## 5 Discussion
Finally, the ambient noise level taken as reference for a sufficient quality of verbal communication also has a considerable effect on the determination of the acoustical capacity. Considering the relation between the vocal effort of a person, the speech level and the ambient noise level, [PERSON] [38] assumes that for normal listeners an SNR \(>-3\) dB would suffice for acceptable quality of verbal communication, however, empirical evidence suggests that a more conservative limit should be adopted for people with profound hearing impairment (which has a higher prevalence on older adults with dementia), thus this approach was adopted in the present application and an SNR = 3 dB was used instead. Where the ISO standard relates the ageing to a shift in SNR of 3 dB, higher levels could be considered, at least for elderly with a profound hearing deficit. Indeed, it has been shown [40] that elderly patients with cochlear implantations show an improved speech perception in noise (44% at SNR + 15 dB, 37% at SNR + 10 dB and 27% at + 5 dB) and additional improvements in global cognitive functioning, indicating the importance of the level of deficit affecting elderly in general, and the strong impact of an improved SNR on their speech perception and functioning. When applying this model in the context of nursing homes living rooms, and calculating the acoustical capacity, the lower level of arousal expressed as higher \(g\) value that would lead to potentially higher levels of occupancy is compensated by a more stringent threshold for ambient noise levels related to the quality of verbal communication for hearing impaired groups. Using a group size value \(g\) = 9, while keeping the acceptable ambient noise level to 71 dB for sufficient quality of verbal communication, would result in acoustical capacity values that are unrealistic (e.g., 200+ people in the living room with reverberation time retrofitted to 0.39 s). On a different note, nursing homes are facilities that function with a relatively constant routine. The living rooms represent the space where social interaction happens and this is affected also by how the NH management plans the activities and the layout of the space (e.g., how tables and other furniture are arranged, what time slots--if any--are scheduled for external visitors' access, how and when food is served, etc.). This implies that many other sound sources are present/dominant at specific times of the day that go beyond human conversation: it is one of the limitations of this study, where further research would require additional processing of the acoustic data to isolate speech and disregard other sources (staff cleaning, trolleys in the room, etc.). Larger deviations of the predicted values from the measured data are indeed observed when moving away from the peak times of activity of the NH living room (i.e., when meals are being served). However, this issue is common to other eating establishments, where conversations are just one of the sources contributing to the acoustic climate of a place and many other non-verbal events are occurring, so, to some extent, the model has to statistically take into account that as well.