The room is itself an acoustic system in the model chain

Evidence

If we are modeling the effect of an instrument being played in a room, then the output we require is the sound heard by the listener and not the output from the instrument itself. The environment itself acts as a sound modifier and therefore it too acts as a “system” in terms of the input/system/ output model. The input to the model of the environment is the output from the instrument being played. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1083

Categorization

• DEFINE: Extends the model to chain instrument and environment as cascaded systems — the basis for room acoustics.
• XREF: connects to: Room acoustics act as a second system cascaded after the instrument — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1059