Go to the" Voices of Experience" forum to get your feet wet, then take a look at some of the discussions we have had in other forums, and finally, John Stevens has put out a tape of the sounds of Kotodama, at least I got one at the last seminar, to go along with the words in "The Secrets of Aikido", by John Stevens.
There are sounds and vibrations within the universe, and life itself, that accentuate and neutralize movement, energy, and power. Some of these sounds are in our practices, but they are not always used in their proper sound to movement application.
Kind of like gaining the focus of a kiai and increasing the force though that focus. Sounds are but the resonance of life, and finding the proper use for each sound ... well ... I am still struggling with that myself.
It is an interesting study, and will increase your lung capacity as you learn to hold sounds for longer and longer lengths of time. So, even on the physical training level it does benefit the practitioner.
Continue your studies, and let the answers come without forceing them to come.