[quote=@Dervish]
<Snipped quote by Fallenreaper>

Most soldiers don't have radios or anything like that, and most helmets don't cover your ears. They're basically meant to prevent shrapnel, that's about it. Usually every platoon has a radio or two (varies from unit to unit), and in the case of armoured reconnaissance like I did, it was a radio per vehicle, or 3-4 troops. Keep in mind most soldiers are in a formation most of the time, and under the command of their section commander, so lots of shouting. 
[/quote]

But, Mass Effect is a Sci Fi setting, like Fallen said, wouldn't technology have reached a point where it's easy for each soldier to carry a radio? Plus, if you look at the helmet they do seem to have enough space to include a radio in them