[Benj]

On Dec 25, 3:25 pm, Uncle Al wrote:

Whispering galleries and inside elliptic reflectors, yes. This is the
preferred way to build confessionals in church - at one focus - with
rentable scholarship rooms at the other focus.

Really? I"m going to have to look into this. I"m thinking I'd really
like to line up a few "scholarship" hours at peak confession times!

Parabolic reflector (satellite dish), not so much. Incoming will be
focused but outgoing will be collimated.

Obviously the "whispering gallery" setup would use TWO parabolic
reflectors which is the equivalent of the elliptic chamber. Both are
conic sections and work nearly the same. A single parabolic reflector
is the usual microphone setup. But a single reflector is the "I see
you, you see me" equivalent of only ONE person with a telescope as
opposed to each person having one. If both persons have similar
telescopes then that is the optical equivalent of a "whispering
chamber". And I might mention that acoustic lenses exist as well so a
reflector isn't essential to create the effects.