Blackhawk v Huey

A flight of three UH-60 Blackhawks performed a flyover this morning
during our local Independence Day parade.
It struck me that they were able to get within one-half mile
(thereabouts) before I noticed the "helicopter" sound.
I had noticed this previously, but had filed it away.
I then got to thinking about the old UH-1 Huey's and how they could be
heard miles before you could see them.
Can someone definitively tell me what improvements were made to the
UH-60's to make them quieter than the UH-1's?
What is it about the main rotor blades and/or tail rotor blades that has
been changed?

In a previous article, john smith said:
I then got to thinking about the old UH-1 Huey's and how they could be
heard miles before you could see them.
Can someone definitively tell me what improvements were made to the
UH-60's to make them quieter than the UH-1's?

The UH-60 has 4 blades, the Huey has 2. Maybe the Huey blades have to
spin faster?


--
Paul Tomblin http://blog.xcski.com/
The superior pilot uses his superior judgement to avoid situations in which he
has to demonstrate his superior skill.

Improvements in blade design and technology have cut sound signature
of helicopters tremendously. The Huey used what can be best described
as a "plank" for a blade. The Blackhawk uses a very different shaped
blade especially at the tips.

Helicopters don't fly...they beat the air into submission.