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Acoustic Feedback and Acoustic
Feedback Deluxe
Introduction
Real acoustic feedback appears when the sound
waves from the cabinet hit the strings with enough
energy (accomplished by playing loud enough) and
with the right phase (accomplished by positioning
the guitar at the correct distance from the cabinet).
The difficult part with acoustic feedback on mod-
erate volumes is therefore to get feedback on the
desired notes—it is easy to get feedback, but if you
for example need to get it on the high D, you have
to find the exact distance so that the string vibra-
tions and sound waves don’t cancel each other. The
rumour is that when Robert Fripp recorded the
feedback parts on Bowie’s Heroes , he made markings
all over the floor in order to find the right position
for different notes...
The Acoustic Feedback simulator is a mathematical
model of real acoustic feedback. We have modeled
how the sound waves hit the strings, how the strings
interact with the amplifier and how the sound
waves travel through the air back to the guitar again.
But the only thing we couldn’t model is the distance
between the guitar player and the cabinet (compu-
ter?). So to solve this we made an “auto- positioner”,
pretty much like a Brian Eno running around with
the cabinet so that Robert Fripp didn’t have to
move between the different markings on the floor.
So with all these parts put together, we present to
you the Acoustic Feedback plug -in!