The first application of a flashing electric turn signal was used on the 1938 Buick as a new safety feature called the “Flash-Way Directional Signal”. The process was based on an engineered “short-circuit”. Electricity flowing through a wire expands it, completing a circuit and allowing current to reach the lightbulb. This short-circuits the wire, which then shrinks and terminates contact with the bulb but is then ready for another cycle.
The flasher unit evolved in design to use bi-metallic spring steel to do the job. Manufactures originally tried to muffle the familiar clicking noise we have become accustom to.
By 1940, Buick added the self-canceling mechanism attached to the steering column as standard equipment. This complex and sensitive mechanical method of springs, cams, sliders and lobes with fixed shut-off points is the basis of what is still used worldwide in virtually all vehicles.
It would not be until the late 60’s that the emergency 4-way flashers became standard.
The solid state technology in today’s cars don’t really need to make that clicky noise, but has remained a remnant from the olden days when bimetallic springs and little electronic under-dash chips and relays did all the work. Today, the clicking noise is added intentionally though the speakers or other means.