espa espa

The rotating chirping bird (1st c. Α.D.)

This was a shrine (temple reliquary) which automatically displayed a bird rotating and singing as the faithful turned the exterior wheel of the case when entering the temple. It consisted of two axles which had two radial wheels that engaged each other and a singing disposition that was mounted on an inverted concave container.
This could be immersed into a container with water. The vertical axis had, at the top, the model of the bird while the horizontal axis had at one end, the driving wheel and at the other end, a reel with wrapped rope from which the inverted container hung. The singing disposition consisted of a bent sound pipe (with a side reed) whose inlet communicated with the base of the inverted container while its outlet slightly penetrated a water dish.
By turning the wheel the bird rotated quickly and the inverted container immersed in the water container so the trapped air escaped from the pipe whistling. Due to the water surface vibration (by the air pressure) at the outlet of the pipe, its sound length fluctuated; therefore, the resulting sounds changed frequency so as to produce a true bird chirp.

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