Abstract:
In 1928, Niels Bohr pointed out the dual description required in the quantum mechanics of measurement, involving the observer and the observed [Naturwissenschaften 17, 483--486 (1928)], and a few years later, John von Neumann discussed this principle at some length in his text on the Mathematical Foundations of Quantum Mechanics [(Springer-Verlag, Berlin, 1932), English translation, Princeton U.P., 1955]. It now appears that architectural acoustics has been following the same route. Examples cited by von Neumann are described and paralleled with examples from the work of Schroeder, Ando, and others in concert hall acoustics.