I cant believe that you find the HJC RPHA 70 noisy???
I have had one for 6 months and love it, it is the quietest helmet I have ever worn and so much better than the Arai Chaser that it replaced.
I am thinking that your screen is deflecting disturbed air flow direct onto your helmet in which case no helmet in the world will be quiet.
Is your screen in the low position? It is the only position that works for me, leaving your helmet in clean air, I am 5ft 10.
Have you tried standing up on the pegs to get your head higher? You may be surprised how much smoother and quieter it is....or try riding a naked bike.
Obviously we all have different shaped heads and have our own preferences for fit and comfort of helmet but the shell of the RPHA 70 is reputed to be one of the quietest on the market and I tend to agree, even with all vents open.
Good luck with your quest for quiet riding