A late C19th model to demonstrate how waves move; made by the Elliott Brothers, to a design by Baden Powell ((1796-1860) – the father of Robert, founder of the scout movement). An interactive animation here.

This — and other explanatory scientific models — can be seen at the seemingly wonderful University of Cambridge Whipple Collection. Here — with a linking thought on the 'sculpting' or 'choreography' of sound waves — an unattributed pair of parabolic sound mirrors, again late C19th.

The principles apply through a history of use, from these almost Neolithic, pre-radar wartime sound mirrors (via Web Urbanist) to today's satellite dishes.

Some lovely examples collected by Web Urbanist, for example this Czech 'acoustic detector', c. 1920.

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