Electronic Ear Plugs
I have a Gallet and use ear plugs that have a small internal speaker inside them. They are connected to the helmet's speakers and everything you would normally hear through your helmet speakers is heard directly into your ear while the benefit of foam style ear plugs keeps the external noise levels down. Because of this, you find yourself turning down all the volumes on the ICS and radios to less than half that you need without the ear plugs.
You need to modify the helmet slightly, but it's a real easy mod to carry out.
Do a Google type search for them.
Or PM me and I will send you the link directly to their website.
Makiwa