By "voice," we don't mean the actual sound the vocal cords produce. Rather, we're talking about the mix of description and style that's unique to a particular writer. Perhaps the easiest way to think about a writer's "voice" is to think about your favorite comedian.
For example, Robin Williams had a certain style, a specific kind of whack-a-doo narrative description he employs, and a delivery all his own. When you hear Robin Williams, you know what you're hearing could only come from his twisted brain.
The same goes for any quality comedian or storyteller -- Chris Rock, Jerry Seinfeld, Jon Stewart -- they all have a unique ring to their storytelling that only THEY have. You hear a joke, and you know it's theirs. What you're hearing is their voice.
The same thing goes for writers. In some cases, you could read an unfamiliar paragraph and know immediately who wrote it. Stephen King's casual delivery, with his quick pace and often brutal description is all his own. Same goes for Ernest Hemingway (short, choppy sentences featuring razor-sharp but simple description); David Foster Wallace (circular, introspective storytelling with maniacal attention to detail); and even Paul Harvey (who spun his slow-to-burn vignettes into "The Rest of the Story," an internationally-known franchise). What sets these writers apart from anyone else -- everyone else! -- is their "voice." So how do you develop your own voice?
First, the good news: Everyone in the world tells stories differently, so everyone will have a unique voice. Only YOU could tell a story in a particular way. This is your voice. The kinds of details only YOU would notice; the kinds of jokes only YOU would include; the way the story builds in only the way YOU would build it ... these are all trademarks of a writer's "voice" -- and this is what will make your writing distinct.
Unfortunately, many writers don't really consider their voice. They should. Ignoring your voice means your piece of writing will sound generic, like anyone could've written it -- like it was designed by committee. What good ever came from something designed by a committee? A piece of writing with voice will always be more memorable than a generic piece of writing. Take the time to add your voice.
Consider the following tips for adding voice to a story:
Next time you're telling a story to a friend, look for what they respond to in your speech. Is it your jokes? Your descriptions? Your philosophical insight? Whatever people seem to be drawn to is part of your voice. Try to emphasize these personal trademarks in your writing.
Try writing exactly as you speak. No two people speak the same way, so practicing to write exactly as you speak could lead to a one-of-a-kind narrative.
Forget that you're writing an assignment for publication, and write as though you're sending a birthday card or email to a close friend or family member. Ignore the "stress" of writing for a living, and simply write. What comes across will likely be your voice.
Read something from a writer you admire. Note what about his or her writing jumps out at you. Write something of your own, emulating this writer. You don't want to just copy his or her voice, but you want to practice using "voice" in a story. Maybe you don't even know what your voice is. Experimenting with writing something light and breezy and then dark and gloomy will give you insight. Which rings more true? Which was easier? Maybe this is your voice.
Now, the (slightly) bad news: Hemingway, Seinfeld, Williams ... none of those people developed their voice overnight. In fact, it took years of practice to nail down their cadence, description, and delivery. It may take you a while to hammer home your voice, too. The silver lining is that you get to play with techniques to find your voice, and that can be a lot of fun.
And always remember: Writing is supposed to be fun.