I've never pretended to understand the aerodynamic properties of rotor craft - it's all magic to me. Our training program included old movies of helo blades taken from the rotor hub out along the length of the blade. After watching the gyrations of a blade while it rotates in flight makes me wonder why I ever continued flying them! There must be some of those types of videos on YouTube & are worth a view.
Rotor blades are subject to enough torture as it is, without subjecting them to supersonic speeds at the blade tips, although they do come close. In those days, blades were made of metal & subject to fatigue due to constant flexing, corrosion & eventual failure if not changed out after so many hours. In fact our unit lost a CH113A Voyageur & crew during a night training trip on base due to a metal blade failure causing catastrophic disintegration of the helo at 500 feet. I had flown that particular machine in the morning & afternoon flights & it came apart that evening - not my time I guess. Today, blades are all composite materials & are much stronger & safer.
The Huey's characteristic sound was from 2 quite wide (chordwise) blades that really compressed the air when coming head on. I heard a 3-ship approaching one day on a cold prairie winter morning at about -35C - the sound was absolutely surreal - reminding me of the 'Apocalypse Now' soundtrack but at extreme levels. It was really quite amazing & I don't think that most HTs could adequately reproduce that awesome sound in all its glory (unless there were a couple of EP800s involved, ha!)...