You brand voice is how your company communicates with the world. You need to have a strong personality and point of view and you have to own it. Confidence is key; this is how you get it.
Establish your character
You can't define your voice until you define who you are. Choose three words as the pillars of your brand and continue to build from there. Decide what you stand for, what you're best at and what kind of people you are talking to. Once you establish your values, your passion will do the talking for you.
Decide what makes you authentic
Most brands/products/services are created with the core desire to solve a specific problem. Figure out what you're solving for and why your solution is better than anything else available. Zappo's made a name for themselves not just by selling shoes, but by showcasing their incredible customer service as a differentiator. That's the kind of story you want to tell.
Make yourself an authority
Don't just sell hats, be a hat expert. Blog about the newest innovations in hat making. Send your customers an email with a guide for which hats to wear in what season. Instagram cute pictures of dogs wearing hats. Compliment what you sell with valuable information that makes you a resource for your customers that builds trust and establishes credibility.