This device converts sound into a visible form- light and movement of the milliammeters. As with all my creations I built this all myself using alot of old parts, for example the meters are from about 1940. I modified the circuitry inside to function better with the meters and the thermionic valves which are modified to light up green and red.
It is activated by a key operated switch and has a solid brass sensitivity "tap" which you can see me fiddling with in this video.