It’s a pretty safe assumption that as long as humans have been around there have been individuals whose hearing went away, either slowly or suddenly. Technological fixes can be found in archeological digs, precursors to today’s microcomputers for the ears.
Ear trumpets, dating to the 17th century, are considered the first “modern” hearing aids. Utterly simple, with one end wide and the other one narrow enough to be inserted in an ear, they simply “cast a wider net” for incoming sound and amplified it mechanically. The first were adapted animal horns or shells — there’s evidence that people had been doing this for centuries already — but during the “age of invention” more elaborate ear trumpets came to be made out of glass, copper, and brass.
Things really took off when electricity was harnessed in the late 19th century (hearing aids and telephones are close cousins, technologically speaking). Though the word harness is a double-edged sword. The first electrical hearing aids meant carrying around a box (or two) of wiring, vacuum tubes, and batteries that would put a pack of modern D batteries to shame.
Then the minimization of electronics that has marked the last century kicked into gear. The commercialization of the transistor after World War II brought on what we now conceive of as a hearing aid — basically, a device that fits in or around the ear and can be worn for long periods of time with minimal effort.
This was a godsend for many people, allowing them to interact and communicate in public and private settings.
And things obviously continued to get better as transistors were replaced by computer chips, introducing digital technology to hearing aids. The ability to convert sound waves to a digital format, manipulate it, and convert it back to sound waves that are amplified into a person’s hearing canal — almost instantaneously — wildly expanded what hearing aids can do. Soon hearing aids could communicate wirelessly with other devices and life for the hard of hearing became drastically less cumbersome and limiting.