Statistically, flying commercially is very safe. Even taking into account the recent Malaysia Airlines tragedies (which were both likely caused by human action - the fate of MH270 is still up in the air, no pun intended), flying is still one of the safest ways to travel. If commercial aircraft were not safe, they would not be permitted to fly.
For noise, it is somewhat dependent on the aircraft. With the MD88 and the CRJ, the engines are located at the rear of the fuselage, so there would be a little more engine noise towards the rear. In the A320, the engines are below the wings, so position in the aircraft is less of a factor. Turbulence is generally the least closer to the front, usually over the wing (though this will depend on the aircraft) - this is likely because of the location of the center of mass.
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"Tongue tied and twisted, just an earth-bound misfit, I" - Pink Floyd
(and then the tower cleared me for take off)