The 'Fathead' engine were totally redesigned from the ground up, and they are completely different from the older EVO's.

And you are right, the noise level of the Fathead's is next to nothing. With louder pipes you don't hear anything out of the engine other than the exhaust tone.

Here is an excellent article by Donny Peterson in which he goes over every upgrade that was incorporated in the Fathead engine, and discussions with Harley engineers.

https://www.hdforums.com/m_491389/tm.htm