Each helo on the boat has its own unique sound. You could tell how the airplan was going by sound alone.The blade cord and airfoil shape. It's a fat blade with a specific shape that seems to cause the tips to snap a lot more than others. The 206 has a smaller cord. The Cobra is close, but I agree, the Huey is still the "singular" sound.
FWIW, I can usually tell a -60 from it's tail rotor. I always find it interesting how each aircraft has it's own sound when you get used to it. The 206 has a distinctive T/R sound, as well.