The PSFC System does not have a direct control for distance.
As a workaround,
we emulate distance function using the available control parameters:
LIVENESS (reflection and reverberation gain),
ROOMSIZE (delay), and VOLUME (source gain).
Figure 2 diagrams the sound level.
Direct, Reflective, and Reverberant Sound
The direct sound arrives first at the ear.
Next, the reflective sound comes shortly after.
The time gap is the initial delay.
It is an important cue in a simulated soundscape,
suggesting the size of an indoors space [Bla96].
In the PSFC System, the ROOMSIZE parameter describes the initial delay [Beg94].