How often did your mum tell you to take a deep breath when you were young and had to say something in public? I know mine did.
What you actually do is breathe in so deeply on top of breath that’s already there that your lungs get the information that you have to breathe out completely in order to take a clean deep breath in.
If you try to speak after the initial deep breath on top of breath that’s already in your lungs you’re going to have to let some breath out anyway before you vocalise and that in itself will reduce the power of your voice.
Why not allow yourself time to do the deep breathing before you get up to speak? No one will be aware of your preparation except you. A simple way of doing this is releasing slowly all the breath from your lungs and then breathing in deeply 3 times. You can count out for 8 while expelling the air and in for 5 before the next breath release.
It’s particularly good if you’re sitting down on a chair with a high back as you can feel the deep air being released from the base of your lungs inside the ribcage against the back of the chair as you breathe out and filling up again as you breathe in. It has the added benefit of taking your mind off all the scary faces waiting in the audience for you to speak. If you’re standing you can still perform the exercise and it has the effect of grounding you and making you more stable on your feet.
With this simple preparation you won’t have too much breath in your lungs and you’ll be able to speak cleanly on your first outward breath.
This plus other simple techniques that we use in our voice training programmes enable you to concentrate at once on what you want to say not how you’re saying it and allow the process to become enjoyable for everyone. While you’ll get sympathy from some of your audience when your nerves are revealed in your voice, most of them will feel edgy on your behalf.
Public speakers require different use of their breath flow to singers. Of course it’s always great to increase your lung capacity and singing is great for doing this but the techniques for delivery are widely different.