I do not understand why they are not using curved tip propellers on the Tu-95. This reduces tip speed and noise. There is no loss of performance that
I am aware of. In fact, the transition supersonic tip regime is a loss of thrust performance.
It is worse than the article describes. At speeds where supersonic shocks are generate there is also cavitation. Similar to the submarine problem.
Contra-rotating propellers make more noise but there is no discussion of a bad mix with curved blades. It is possible curved blades would amplify the
noise associated with the contra-rotating configuration. But I think the trans-sonic shock regime is worse for noise generation, considering cavitation.