I think it is an information problem.
One of the issues arising in Ramage and Chapman is the question of whether information has to involve people. In one of the chapters, John Monk says:
“The word ‘Information’ derives from human intercourse” therefore the term “information” in other contexts is used in an “anthropomorphic sense”(Engelberg and Boyarsky, 1979).The distinction between sound as something a person hears and sound as the pressure waves is the distinction between 'physical (Shannon) information' and 'semantic information'.
The system can be modelled by my layers and trapeziums. The pressure waves are at a lower level and take on the meaning of 'sound' in the human brain.