Sound tends to "bend around" non-porous, small obstacles.
Large surfaces such as the boundaries of rooms are typically
partially flexible and partially porous. So, when sound strikes
such a surface, some of its energy is reflected, some is absorped,
and some is transmitted through the boundary and again propagated
as sound waves on the other side.
All three effects may vary with frequency and with the angle of
incidence. Mostly, they do not vary with sound intensity.
Over the range of sound pressures commonly encountered
in audio work, most construction materials have the same
characteristics of reflection, absorption and transmission
whether struck by weak or strong sound waves.