Are there any true effective ways to reduce the noise of a Mooney?

[A64Pilot]

One of my aircraft in my first troop, 85-25454, I remember it because it was a Big Block Chevy.

Anyway it’s assigned pilot was real concerned because at high torque and airspeed, it was terribly loud, he thought there must be something wrong with the rotor system, turned out that the window over the pilots head was flattened, maybe due to heat, but anyway at high air speeds the rotor wash beat on it like a drum head.

On other aircraft a thicker windshield can significantly quieten them, I should imagine it would quieten a Mooney some too.