Think before you open your mouth
One of the reasons we mutter our words is that we haven’t really thought about what we’re going to say. Then, when we open our mouth to speak, we try to hide that fact by turning down our internal volume control. Which results in the words coming out indistincive, weak and blurry.
Pausing, even for a millisecond or two, and engaging your brain before you open your mouth is a good way to help overcome this issue. The brief pause allows you to collect your thoughts and even if they’re not perfectly organized they will at least be more coherent than they would have been otherwise.
Standing – rather than sitting – helps your confidence and this will come through in your voice. If you’re on the phone, clench one or both of your fists as this will make you sound more authoritative. It looks a bit over the top in a face to face conversation though!
And remember to smile – that will come through in your voice. If you’re standing next to someone it will make both of you a little bit more relaxed which will help your confidence and that will, in turn, make its way into the way you’re speaking.
Use your full voice
For many mumblers, the art (or lack of) of speaking starts near the top of their throat. Which doesn’t allow any air build-up and doesn’t give any power to your voice.
Take a nice, slow, deep breath before you start talking. Think back to point one and use this short time to gather your thoughts. Then speak from your diaphragm rather than squeak from your throat. You’ll be pleasantly surprised just how much louder your voice gets just from this.
Slow down, you’re going to fast
Mumbling often goes side by side with speed talking.
You don’t want to sound like a human version of Speedy Gonzales, rushing out your words incomprehensively at 90 miles an hour.
Allow your words to be separated by brief pauses. Not so long that the person you’re speaking to thinks it’s their turn to speak or gives up listening to you from total boredom. But long enough to show that you haven’t just run all your words together in one single, almost certainly incoherent, babble.