Why does screaming on a ride help?

I know tons of people scream for fun but I know plenty who scream so that it's not as scary. Whenever I go on roller coasters that launch with one of my good friends she always takes a gigantic breath and screams so loud my ears feel like they're going to explode. Same goes with the drops. Why does this seem to help her (so she says). It hurts my ears! LOL.