The discovery that electrical stimulation in the auditory system can create a perception of sound occurred around 1790, when Alessandro Volta placed metal rods in his own ears and connected them to a 50-volt circuit, experiencing a jolt and hearing a noise "like a thick boiling soup.”
Ouch. That’s a terrible mental image.
The first direct stimulation of an acoustic nerve with an electrode was performed in the 1950s by the French-Algerian surgeons André Djourno and Charles Eyriès. They placed wires on nerves exposed during an operation, and reported that the patient heard sounds like "a roulette wheel" and "a cricket" when a current was applied.
Ouch again. But, I have to say, I’ve heard that cricket!