ven·tril·o·quism 
(vĕn-trĭlə-kwĭz′əm)
(vĕn-trĭlə-kwĭz′əm)n.
The art of projecting one's voice so that it seems to come from another source, as from a wooden figure.
[From Latin ventriloquus, speaking from the belly : venter, ventr-, belly + loquī, to speak; see tolkw- in the Appendix of Indo-European roots.]
ven′tri·loqui·al (-trə-lōkwē-əl) adj.