Noise was a huge factor with the previous experimental engine, the high-subsonic tip speeds generate quite a roar and as the Tu95 more than amply demonstrates, the clashing soundwaves from contrarotation seem to really kick it in high gear...though you would think that, at least from some angles and at certain speed/pitch combinations, it should be possible to engineer it so the the sound waves cancel out.
If I had the time I could give you about a dozen good sound engineering reasons why this is a "really bad" idea from a commercial aircraft point of view.........efficiency notwithstanding, it would never actually be practical without a "shroud" on the exposed blades to prevent low-speed "blade stalls", and I agree, the noise would be astronomical......the additional weight of the extra sound deadening material to make parts of the cabin livable would cancel out the efficiency gains......
Back in the '50s Lockheed experimented with a VTOL aircraft with a turbine mounted in the nose and counter-rotating props.......the noise level in the cockpit approached 180 dB, and other than a bunch of other failings, it was unbearable to attempt to fly.
The blade shape is similiar to a Russian design for one class of their Nuke subs, also with counter rotation, and they could never solve the noise problem either, even at very low RPM....
doc