Different scholars have different ideas about how the name YHWH was originally pronounced.
In The Mysterious Name of Y.H.W.H., page 74, Dr. M. Reisel said that the "vocalisation of the Tetragrammaton must originally have been Y e HuàH or YaHuàH."
Canon D. D. Williams of Cambridge held that the "evidence indicates, nay almost proves, that Jahwéh was not the true pronunciation of the Tetragrammaton . . . The Name itself was probably JAHÔH."—Zeitschrift für die alttestamentliche Wissenschaft (Periodical for Old Testament Knowledge), 1936, Volume 54, page 269.
In the glossary of the French Revised Segond Version, page 9, the following comment is made: "The pronunciation Yahvé used in some recent translations is based on a few ancient witnesses, but they are not conclusive. If one takes into account personal names that include the divine name, such as the Hebrew name of the prophet Elijah (Eliyahou) the pronunciation might just as well be Yaho or Yahou."
In 1749 the German Bible scholar Teller told of some different pronunciations of God's name he had read: "Diodorus from Sicily, Macrobius, Clemens Alexandrinus, Saint Jerome and Origenes wrote Jao; the Samaritans, Epiphanius, Theodoretus, Jahe, or Jave; Ludwig Cappel reads Javoh; Drusius, Jahve; Hottinger, Jehva; Mercerus, Jehovah; Castellio, Jovah; and le Clerc, Jawoh, or Javoh."
Thus it is evident that the original pronunciation of God's name is no longer known. Nor is it really important. If it were, then God himself would have made sure that it was preserved for us to use. The important thing is to use God's name according to its conventional pronunciation in our own language.