I also have a Neotec II, and 5 other helmets. I wear ear plugs under my helmets, too. However, after experiencing hum or drone as some call it, I started experimenting with different ear plugs, from the cheapo disposables, to the type that you heat and mold to your ear. But, I found certain brands eliminated the drone, while others not so. The expensive ones were no better than the cheapos. And results varied from helmet to helmet. Everyones heads are slightly different, as are our ear canals. What worked for me may not work for you. Just try several different ear plugs, if you ride with them. No drone noise in my head. Makes the ride better.