First off if this is on the 250/300, then you need a better helmet. My current one is the quietest helmet I've ever owned, most are very poorly designed for noise even VERY expensive ones. I wish the type approval tests had DB ratings for all helmets, I have been very disappointed in the past with some helmets I have owned or borrowed. You should be able to hear easily with good buds up to 80mph, above that even good acoustic helmets start to generate lots of noise.
Active noise cancelling is the next thing to take it to the next level, I use Boseir over ear units on planes & have been waiting for a helmet manufacturer to bring one out. Sena announced one a couple of years back with full noise cancelling & built in bluetooth comms etc, but its not arrived in the market yet
YMMV