Rooms That Answer Back

[A] A concert hall is an instrument that the audience sits inside, and the quality people call warmth is mostly a matter of time. [B] A note reaches the listener directly and then again, a fraction of a second later, having bounced off the walls and ceiling. If the delayed sound arrives within about eighty milliseconds of the first, the ear does not register it as a second event at all; it folds the reflection into the original and reports a single fuller tone. [C]

[D] This is why the shape of the room matters more than its materials, and why the halls that succeeded were often narrow. A narrow hall puts the side walls close enough for the first reflection to arrive inside that window, and a wide one does not, whatever it is lined with. The lesson was learned slowly and expensively, because the difference cannot be heard in a drawing, and the buildings in which it was tested cost far more than any experiment could be asked to justify. Several of the halls now held up as models were built by architects who had no theory of why they worked, and several that were designed with the theory in hand have never sounded as well.