Voice From Inside A Helmet

What effects would I use to make a voice over sound like it’s coming from inside helmet?

I’m at work so i can not really play around with it.
Though If you use an eq to remove the higher frequencies will give it some of the qualities from a helmet because higher frequencies tend to travel in a “line of sight” way more than lower frequencies. This can be used for the outside a club effect too, where u really just get the low frequencies until a door opens and then u get the rest of the sound.