The results of previous animal research indicated that the mammalian ear is able to hear pitch and amplitude with great accuracy when a uniform audioelectrical field is applied to the basal membrane. Four patients were tested with electrodes placed temporarily in the lower scala. Two heard only noise when stimulated with sine waves and were eliminated from any further procedures. The other two exhibited a remarkable ability to discriminate pitch and amplitude. Later, they had a permanent internal system implanted. Pitch and amplitude discrimination was almost normal. Dynamic range was stable at 30 dB. Bekesey audiometry was repeatedly and consistently performed without difficulty. Speech recognition was immediate, but information was low. Nevertheless, both patients were able to perform certain speech recognition tasks with results above the chance level.
Michelson RP. Electrical Stimulation of the Human CochleaA Preliminary Report. Arch Otolaryngol. 1971;93(3):317–323. doi:10.1001/archotol.1971.00770060455016