A.  Sensual "input" while sleeping is  incorporated into dreams.  Most
notably, while sleeping,  you hear as well  as while waking - the ears
are never turned off. This leads to the consequence that what you hear
while sleeping, you'll hear in your dreams. The sound is always coming
from "somewhere".  Common   experiences of this  kind  are a telephone
ringing or music from the radio.  The same holds for the other senses.
Note  that it is not important  how loud some noise  is to get noticed
while sleeping -  even  an otherwise  unnoticed  sound, like  a  mouse
running over your   floor,  can wake you  up  if  it  is   uncommon or
otherwise alarming to you - on the  other hand, you can get accustomed
to   high levels  of  noise,  like construction   work nearby.   (What
definitely will wake you up is someone knocking  at your window if you
live at the 10th floor ;-)

It is an  interesting experience  that you can  hear  exactly what  is
going on, but  will forget it on  waking up along with  forgetting the
rest of your dream. This includes things  such as news broadcast heard
on the radio - after waking up, you have  forgotten it. It is like you
have dreamed the news broadcast as well - but distinguishing this fact
is a  good  clue to  lucid  dreaming and   the way  "lucidity inducing
devices" work.

Some parts © 2009 Advameg, Inc.