Good communication skills include the ability to project easily, articulate clearly, speak at the right pace and express your self with confidence and credibility. Mumbling undermines all four of those qualities and it’s easily one of the main problems I see every day.

Mumbling is caused by speaking too quickly, speaking too quietly and not opening your mouth far enough when you speak. In fact, a lack of openness, by itself, makes your voice weaker and makes you prone to speaking faster, so just opening your mouth further reduces the tendency to mumble.

Obviously, you can’t just force your mouth open because that would look really stupid. It has to be a relaxed openness. It has to feel natural. But since many people just want to jump to the result, here’s what I suggest.

Speak two or three sentences, observing your mouth in a mirror. On average, how far apart are your upper and lower teeth? Ideally, you want to have one finger-width of space between your teeth. Some sounds have more, like ‘hi,’ some less, like ‘he,’ but on average, a finger-width.

For practice, you should go for two finger-widths, very open. I can’t over-stress the importance of using a mirror. You’d be surprised at how easily your mouth starts to close up. If you’re not watching a mirror, you don’t even know it.

Start with single words, such as ‘spa,’ ‘had’ and ‘high.’ When that isn’t so hard, move to phrases, such as ‘Ma’s spa,’ ‘bad ham,’ or ‘my pie.’ When you’ve got the feel of that, try sentences, such as, ‘My father has wide eyes,’ making sure you’ve got a least a thumb-width of space between your teeth on the stressed vowels.

When sentences are easy, try reading paragraphs in front of a mirror. Remember, you’re looking for an average of one finger-width of space between your teeth. When that’s a familiar feeling, try speaking with more openness in everyday conversations.

If you haven’t been speaking with a relaxed sense of openness, this will feel strange and unnatural. That doesn’t mean it’s wrong; it’s just different. You’re not used to allowing sounds to emerge from your body with so much space. You need to practice this in private until the feeling is familiar, until it feels like you.

When you’re able to speak in public with a relaxed sense of openness around your mouth and jaw, your voice will be stronger, because more openness leads to more breath support. Your articulation will be clearer, because more openness encourages more precision. You’ll speak at a relaxed pace, because more openness slows you down. And you’ll appear strong, confident and credible. These are all crucial communication skills—and all have a connection to opening your mouth.

You know I hate gimmicks, shortcuts and superficial tips, but this is something anyone can understand, and it’s not hard to practice. So open up and, as your mother would say, “Stop mumbling!”

For more information, and exercises to improve your communication skills and reduce mumbling, visit voice and speech dot com, and enroll in the free video mini course, The Sound of Success.