As the “author” of The Tao of Blogging, I concur wholeheartedly!
After reading all the answers and making the sound while thinking of how the mouth moves to create a sound, there is definitely no “pa” sound. And the “awoo” sound is much closer to a wolf, so that is too confusing.
Simple consonant sounds where the lips end up open, followed by a long continuous vowel sound seem to make the most sense:
“hneeeee” is really good. As is “breeeee,” or “bweeee.” I can hear that sound used for a higher pitched elephant, like a baby or a female.
For the bull elephant, maybe a deeper sound like “brrruuummmm” could work.