Assuming the reason is sound proofing. Just stick 2 solid core doors on the same frame. But both opening away from eachover. And line the inside faces of each door with sound adsorbent foam. So when both doors are closed, you have the equivalent of Solid wood - Foam - Solid wood.
I can't see how a sliding door could possibly be better, as when the door is closed, you have an empty cavity that you can't fill with sound insulation. Unless the building design means that a cavity slider is the only option.
I would have thought that the first step would be improving the seals on the door (virtually none on a domestic interior door), before beefing up the door itself. Cavity sliders are relatively expensive, so you'll get more bang for your buck with a beefy hinged door and good seals. Could use something like this automatically closing bottom seal