The Vocal Mixer can be accessed via the pause menu. Using the mixer, you can adjust the volume of your own voice, as well as change the reverb preset.
There are 4 Reverb presets (Room, Club, Arena, Cathedral) that each have their own sound. Experiment to see which one you like the best.
If you don’t want to hear reverb, simply press the active reverb preset and the reverb will be turned off.
Please note that reverb and your voice are only audible with headphones with a built in microphone.