I'd imagine Barraza having a young adult sound with a medium to low vocal range, and a grumble in his voice that makes him sound like the powerful, commanding leader of a gang, or the main villain in a Mad Max movie.

Lore:

The apocalypse came not on a missile but a mist. MBFC's self replicating nanobot cloud bricked everything that relied on computer circuitry, which in 2150 was everything. Deployed on a rogue agent's hideout, the weaponized mist was supposed to become inert after twenty minutes.

Fifty years later, Barraza was born in an abandoned aircraft carrier outside the girder wastes once called Los Angeles. Soon waterhaulers, warbangers, zealots, radsuits, wastecroppers, junkers - all came to fear the wild man they called Diesel Heart.

Shot in the chest by The Fuel Lords and left for dead, he returned, kept alive by an iron will and an artificial heart burning diesel. Soon the Fuel Lords were dead, followed by the Ravagers, the Scorpions, the Battleborn, and every other challenger until Diesel Heart ruled the wastes from Four Face Mountain to the Steel Wall.

The ultimate survivor, Barraza knows Valhalla is another threat to overcome through violence and will. The next apocalypse is coming, and he will do what it takes to come out on top again.