Currently I am researching ways to build a sound activated system.
 
Type of experiment:  Build a board that controls a paintball loader.
 
Criteria to be met:
 
1.  It has to detect sound and activate a 9 volt powered hobby motor that could be found at any radio shack.
      
2.  Once it has been triggered by sound, the motor will remain active for a solid 1 second interval then stop running.
 
3.  If the sound is consistent, the motor will continually run until said sound has ceased.
 
4.  Must be able to use two 9 volts.
 
5.  Needs to be fairly small.

There are boards on the market sold just for this in the world of paintball, however, I am interested in building my own for use in side projects.
Also the cost of those boards are around 60 bucks, so that's another reason I want to make this work ( hopefully cheaper).
 
If anyone can think of the simplest and cheapest way to put something together, I would greatly appreciate the input.
                                                                
                                                                        --- Many thanks,