  We discuss the possible role of quantum horizon fluctuations on black hole
radiance, especially whether they can invalidate Hawking's analysis based upon
transplanckian modes. We are particularly concerned with ``enhanced''
fluctuations produced by gravitons or matter fields in squeezed vacuum states
sent into the black hole after the collapse process. This allows for the
possibility of increasing the fluctuations well above the vacuum level. We find
that these enhanced fluctuations could significantly alter stimulated emission
but have little effect upon the spontaneous emission. Thus the thermal
character of the Hawking radiation is remarkably robust.
