
Reasonably fancy.

Standard "voice" circuits run at 56kbps inter-exchange in the US.
Therefore, you need to achieve 4:1 to get standard voice quality.

If you're willing to give up some quality, you need only 2:1.  This is still
acceptable from a speech standpoint; it will be a little less faithful to
the original, but certainly intelligable.  That's all you really need for
this application.
