Because it is difficult to give an accurate description of the scene depicted here, one must resort to a technical statement. Among the many wheels and gears in this object are two cams. They move at different speeds although they both act on the same lever. Only when the profiles of both cams are in alignment will an action result. Sometimes something almost happens, then ceases to happen. At other, rarer, times the full effect of the cams is evident. The machine contains a 12 volt rechargeable battery which should provide enough power for several months of normal service.
Words beginning with the letter B are particularly difficult for ventriloquists to pronounce. They will avoid closing their lips by using a substitute sound [b’]. In order to replace the explosive characteristics of [b], the tip of the tongue will first be pressed towards the front teeth until the tongue reverses with a sudden movement. The vocal tract is reduced by the distance between the lips and the teeth.
Those wishing to know more about the physics of ventriloquism may find this article of interest.
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Paul discusses the piece in this video.