The S76 is a loud helicopter. There are two things going against it. The first is weight, and the more weight on the rotor blade, the stronger the vortices off the tips. That's the thump-thump-thump the main rotor makes. The second reason it makes so much noise is that the blade design is old.
The Agusta 139 is an even heavier aircraft, yet it is far quieter, at least seemingly so to me. If you take a look at the blades, they are similar(ish) to the raked wingtips of the B777. Many of the modern propellors also use this design. These tips reduce the vortices and increase efficiency. These high velocity vortices on the rotor blades are the primary source of the noise. The tail rotor is also a large source of noise, as the tips are nearing the speed of sound. These blades are also evolving in design becoming quieter.
The new S76 "D" model will be out soon. The new blades should be far more quiet.
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Originally Posted by stratoduck
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