Would be to buy yourself a good stud finder. Use it to find the location of the floor joists under your wood floors. Then drive 10 penny screw shank nails through the flooring into the floor joists. Do a small area first to be sure it is working. You may have to predrill the flooring to prevent splitting.
You may never eliminate the squeeking or crackling completely. Put down a heavyweigh 5/8 inch rebond padding under your new carpet to minimize the noise.