This Idea starts by pointing out the existence of a "speaker"
technology that uses ultrasonics (produces sounds that cannot
be
heard). See the first link. The ultrasound interacts with the
air
in such a way that the air becomes the source of the sound --
more, a particular point in the air
can be the source of the
sound.
So, equip a podium with a hidden ultrasound speaker system,
such
that the ultrasound waves are aimed at the microphone(s) on
the
podium. Audible sound would be produced in the air just next to
the microphone(s).
Your victim steps up to the podium to make a speech. He or she
positions his or her mouth near the microphone(s) on the
podium,
and he or she has ears that are not near the microphone(s).
When
you activate your ultrasound beam, he or she will not be able to
hear the sounds produced --but the microphone(s) on the podium
will hear those sounds.
So, you have secretly recorded many prior speeches made by
your
victim, and have edited your recordings appropriately, into
sound-
bites you can individually select from your remote-control panel
for the ultrasonic speaker system built into the podium.
Whenever the person speaking pauses to take a breath, you have
an opportunity to put additional words into his or her mouth --
and
they will be his or her own words, too!