Next, in order to come forward with the issue of indoor noise
assessment, the WHO [2] proposed a default reduction of outdoor
noise by 21.3 dB(A) for single-glazed and 22.2 dB(A) for doubleglazed
windows, as an estimation of the indoor noise levels. As
we simultaneously measured inside and outside noise levels during
nighttime, we were able to assess the validity of this procedure
in our sample. For this purpose, we chose to use the timeframe of
11 PM–07 AM, as the default reduction value is intended to be applied
on fixed timeframes. No significant differences were found
between the actual and the estimated indoor noise levels.
However, this result seems to be coincidental as established on
the individual level where the correlation between the average
actually measured inside noise level and the estimate of it, was
non-significant. This indicates that, in our study, the estimated inside
noise levels based on outside noise levels do not represent a
valid alternative for actually measured noise inside the bedroom
place.