Very interesting exercise
but I'd have to agree that aside from the academic point of view, the benefits are dubious.
The only reason nature uses flapping based propulsion systems is that nature cannot produce an infinately rotational ball joint.
Even the helicopter, which beats the laws of physics into submission, rather than working with them like the plane wing is vastly more efficient than birds at powered flight.
This is down to the fact that rotors, propellers and jet turbines can continuosly rotate in one direction. Birds and insects lose a tremendous amount of energy each time their wing reaches the end of its travel, as they have to then put twice that energy back in to change its direction.
I'm also struggling with the concept of noise reduction. Surely anything that flaps its wings at such a high bmp is going to generate an enormous amount of noise? If you think about it, the wing is a relatively flat surface moving back and forth at a high frequency - just as the surface of a speaker cone does.
We've all heard the disproportionate amount of noise something as tiny as a blue bottle generates? And the blue bottle has no engine noise.
As with most DARPA projects I read about though, I love it! Practical? Nah! Fascinating? hell yeah!
I would certainly be interested to hear more about wing resiliancy in comparison to rotors though. I suppose it depends on the makeup of the wing itself, more than anything else.