A heroic voice is the confident "I've got this!" voice that swoops in when the situation is not looking good to raise hope and bring assurance that everything is going to be okay.
Whether it's an action movie, a war epic, an adventure or even perhaps a horror, there will be a moment when everything is crashing down. The situation seems dire, it looks like the bad guys have won and the team or village or country is starting to descend into despair. That is the prime context for a sure and steady hero voice to step in with an award-winning speech, battle call or picture of hope to unite the people around them and inspire the confidence needed for things to be turned around.
The heroic voice inspires the audience and makes them believe while also filling them with excitement for what is to come. It will often come from a pleasant-looking character and so also fill you with admiration or euphoria, even a sense of crush. You will want to be that character or you will want that character to notice you.
The characteristtics of the heroic voice are a strong sense of confidence which comes through as sure and steady and unbroken. There will be an absence of hesitation or crackling in the voice. This voice tells us everything is going to be okay and we believe it.
Think Denzel Washington, Tom Cruise or Robert-Downey Junior. Sigourney Weaver in the Aliens franchise, Charlize Theron or Michelle Oh.