the whole scene conducted through walls
He can make out just the whistly fricatives of Charles Tavis’s distant voice from behind his double office doors; it sounds somehow like he’s speaking to more than one person in there.
Context
An entire family drama reaches Hal as acoustics leaking through oak: Avril's doorless office broadcasting the girls' diddle-check, Tavis's voice reduced to "whistly fricatives" behind a double door, later even his smile arriving as sound ("The audible smile"). Nobody in this building addresses anyone directly; contact happens by overhearing, meaning inferred from muffled consonants and the shape of a pause. The architecture itself is a communication apparatus that delivers everything and connects no one.