Some school teach another type of breathing method; breathe out with sounds.
The most famous one is "Tohokami (To-ho-ka-mi)".
By the way, I think this "sound" issue needs some explication for the reader who have no idea about Japanese language.
The Japanese language has only 5 vowels: a, i, u, e, o.
In Japanese, when it is spelled "a", it is NOT pronounced as "a" in "able" but as "a" in "aha". "I" is "e" in "we", not "i" in "item". "U" is "oo" in "soon", not "u" in "uncle". "E" is "e" in "get". "O" is "o" in "old". There are loads of websites with audio files explaining how to pronounce Japanese words precisely. Please find professional guidance about Japanese pronunciations. This is very important factor to master Zo-Kiko Tai Chi, so please help yourself to basic Japanese pronunciations. For those who have no idea about Japanese language, to know about its pronunciation, especially vowels, will be key to master Zo-Kiko Tai Chi later.
All right, return to the main subject about "Tohokami".
Originally, it was "To-ho-ka-mi-e-mi-ta-me", the Old-Shinto's Tohokami-ko which is to chant "Sansyu-Haraekotoba (three kinds of purification words)", which was popular at the last days of the Edo era.
And if we go further into the history, we can trace the word "Tohokami" back to ancient times. It is said that the origin of the word "Tohokami" is a Japanese ancient fortune-telling method using turtle-shell, which is called "Kiboku".
This Old-Shinto method chanting the word which has power has long been out of use. But owing to the recent boom in religion and spirituality and some Aikido practice methods and so on, it has lately drawn considerable attention.
General beliefs about the origin of the word "Tohokami" is "Tohokamiehitame (To-ho-ka-mi-e-hi-ta-me)", a name of Kami, a spiritual essence commonly translated as god, in a Shinto epic called "Hotsumatsutae (Ho-tsu-ma-tsu-ta-e)". It is said that if each sounds and words stand for a Kami (God) in Shinto epic, it can be "To-ho-ka-mi-e-hi-ta-me", a god in Hasshin (8 Gods), rather than "Tohokamiemitame (To-ho-ka-mi-e-mi-ta-me) , a god in Nanashin (7 Gods).
Some say it was originally "Tohokamiehitame (To-ho-ka-mi-e-hi-ta-me)", and became "Tohokamiebitame (To-ho-ka-mi-e-bi-ta-me) which later became "Tohokamiemitame (To-ho-ka-mi-e-mi-ta-me). Anyway, it does not make much difference to master Ki energy, so take it any way you like.
Explanations of Old-Shinto, the power of words and a shinto epic "Hotsumatsutae", will be never-ending, so if you are really interested in those topics, please drop into a bookstore or a library and refer to the books specialized in those field for further information. A book store at Yaesu side of Tokyo station is recommended.