The only way a ventriloquist speaks differently is that he forgoes using his or her lips, and learns to reproduce sounds using the tongue, upper palate, and teeth only. Those 'difficult' letters are B, F, M, P, V, W, and Y.

All By My Selves: Walter, Peanut, Achmed, and Me (ed. Penguin, 2010) - ISBN: 9781101189283