Ventriloquism is an act of stagecraft in which a person manipulates his or her voice so that it appears that the voice is coming from elsewhere. The act of ventriloquism is ventriloquizing and the ability to do so is commonly called in English the ability to "throw" ones voice.
However, the term "throwing one's voice" is misleading because it implies that a sound's physical origin has changed, when really the change has been perceptual and not physical.
The illusion of ventriloquism is just that, an illusion. A ventriloquist is skilled at speaking without moving his or her lips. The audience therefore actually detects the sound of the voice from the ventriloquist’s mouth but sees only the mouth of the puppet moving. Thus, two modalities are in conflict. Vision detects the location of the speaker as distinct from where audition (hearing) localizes the speaker. When these two modalities are in conflict, our perceptual system must resolve audition in determining where objects are located in space. The unconscious mind, therefore, resolves the discrepancy between these two modalities by hearing the voice as if it is coming from the moving mouth of the puppet. This short-term change in perception is called capture. This specific capture concerning ventriloquism is an example of ‘visual capture’ because the visual system dominates the auditory system.
While the illusion is extremely convincing, ventriloquists do not actually have the ability to ‘throw’ their voices. However, they are skilled at deceiving audiences through their practice of speaking intelligible sounds without moving their mouths and moving the dummy’s mouth in synchrony with the sound of their own voice.