A healthy voice is a resonant voice. Depending upon the type of resonance, a resonant voice likely is a healthy voice. When resonance is not present, or is not consistent in the voice, the speaker or singer is probably using less than efficient technique that is leading to poor habits that may be causing tensions in the muscles supporting vocal function.
So what do you do about it? How do you find and maintain resonance in your voice?
The first thing you want to do is find the region of your optimal speaking pitch. There are a number of tests for this that you can attempt on your own, though it usually is best to be evaluated by someone who understands optimal pitch.
Spontaneously say, “Mm-hmm.” The trick is to be spontaneous and genuine. The most difficult thing for humans to do is to be “real” on demand. The “Mm-hmm” can take on the quality of the cat with canary situated squarely in the throat when not uttered completely spontaneously. The “hmm” part may be in the region of your optimal pitch, or may be your optimal pitch. Be sure not to grunt the “Mm-hmm.” If you feel your abdomen tighten and a tightness or fullness at throat level, you are grunting the response.
Spontaneously sing Happy Birthday. (See being real, above.) The song may be centered in and resolve in the area of your optimal pitch.
This next one can be tricky unless air is taken in correctly, the throat remains comfortably open and breath is released with the sound. From a few tones higher than you may normally speak, slide (like a slide whistle) down on a sigh-like hum. (Avoid the cat and canary, as above.) Lightly place your fingers on one side of your nose. One of the pitches somewhere in the slide should buzz your nose more than the rest of the slide. That pitch may be your optimal speaking pitch.
In his book, Change Your Voice, Change Your Life, Dr. Morton Cooper tells us about his Instant Voice Press, or Instant Voice Jiggle. He has detailed this technique for finding correct speaking pitch here. http://www.voice-doctor.com/voice-disorders/instant-voice-jiggle-exercise
Once you have found where you should be speaking, try this exercise to optimize resonance. This is best done with a piano and under the guidance of a voice professional. On the syllables “Ming-ee-ay” sing a 5-note descending scale. Start in a comfortable range and alter the five tone scales. You don’t have to be a musician to try this. But do stay in the area just above and just below and including your newly discovered optimal speaking pitch. Your tongue should be positioned propped gently against your bottom teeth, tip down. The sides and front of your tongue just behind the tip should fall into a sort of a forward wave configuration and should remain there. Sing “Ming-ee-ay” on each of the five notes as you descend. Do not press your tongue forward. The feeling of the exercise should be like a hum or buzz – much like barely touching a piece of metal against a running washing machine.
Once you find your enhanced resonance, notice how you have arrived at it and work to establish the same set-up throughout your speaking or singing voice. Keeping the easy hum or buzz in your voice will contribute to your vocal health and ease of production. And go ahead and cup your ear. At the very least, it looks impressive.