I have created my own scale for helmet "quietness"
I consider a helmet to be quiet if you can listen to a radio station or a talking book and understand what is being said without it sounding "loud"
My Schuberth C3 fits that up to about 80km (50 mph) effective wind speed. ie 80 k in the calm, 100k with a 20k tail wind etc.
After that I can hear music if turned up
anything over 115k the music has to be too loud to listen and enjoy.
After 120-125 I need ear plugs
Lucky for me I generally travel at about 105-110 k so unless I am pushing a head wind I can generally hear my music nicely but could not listen to a radio station
That is on my F800GS with the standard windscreen and a laminar lip.
My C3 had one hot spot but is good now and love the helmet after almost 3500 miles. I did have issues with the constant fogging of the sun shade. I had to clean it every two or three days. I sent Schuberth an email and they gave me the option of replacing the shade with a like shade or with a shade with no anti-fog coating. I chose the shade with no coating and have had no problems for three weeks.
I also read on one of the forums that they have developed a new ratched system for the visor. I asked for it because the visor will no longer stay up. I received it in three days and plan on installing it this weekend.
The helmet might be quiet but I always ride with foam plugs. I already have tooo much hearing loss from serving on a Navy carrier for 2.5 years and 35 years of a fireman (those sirens can make your eyes water).
Schuberth customer reps are the best of ANY company I have every dealt with and that says a lot for my 62 years.