Stranded vs Solid Copper


I am making a home made outlet box with Hospital grade receptacles. I am hard wiring into the existing outlet box that was poorly installed.(to far recessed) Does it matter if I use solid or stranded wire for the extension wire/cord in terms of its effect on sound? The length is 4’ to 5’
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The electrician should have used an extender or spacrs to make the receptacle tight not simply use the face plate screw to hold it but nothing new there. The patio home I moved in this year I went around and had to fix about half the receptacles and switches with spacers to tighten them. 
Thanks for the input... you've given me some new ideas. I'm going to mount an exterior metal box with a solid cover over the top of the existing outlet box. Then I'll run a piece solid cooper romex in conduit horizontally over to another surface mounted box with hospital grade receptacles that is directly behind my rack/entertainment center.
Then when it is time to move, (rental) I'll remove the exterior boxes (5 screws) and conduit and restore the crappy receptacle the was originally there.
djones51.. I’ve used small diameter copper tubing as a spacer in the past.. works great because you can custom make your lengths.
As for some of the other comments.. I’ve built a number of homes myself and have functioned as my own electrician under a friends license. Not particularly worried about burning the house down. Just trying to get a good solid connection for these new power cords I recently purchased.
You can use Wiremold, would look a lot neater IMO than EMT tubing. Use the starter box over the outlet, then run the channel housing the bare conductors along the wall on top of the floor moulding and up to a Wiremold surface box that holds the HG receptacle.