Brainwave
entrainment
or "brainwave
synchronization,"
is any
practice
that
aims to
cause
brainwave
frequency
to fall
into
step
with a
periodic
stimulus
having a
frequency
corresponding
to the
intended
brain-state
(for
example,
to
induce
sleep).
It
depends
upon a
"frequency
following"
response,
a
naturally
occurring
phenomenon
where
the
human
brain
has a
tendency
to
change
its
dominant
EEG
frequency
towards
the
frequency
of a
dominant
external
stimulus.
Such a
stimulus
may be
aural,
as in
the case
of
binaural
beats,
monaural
beats,
and
isochronic
tones,
or else
visual,
as with
a
dreamachine,
a
combination
of the
two with
a
mind
machine,
or even
electromagnetic
radiation.