With the rise of electronics in the latter half of the century, we now have hearing aids and cochlear implants to aid those who are hard of hearing. But what existed prior to those devices, if anything? How did hearing aids/cochlear implants come to be developed? Were there any alternatives that were developed that didn't catch on?
My apologies for the delay in answering this! I'm about to head off on vacation so this is going to be pretty slapdash.
Hearing technology prior to transistor-based hearing aids was predominantly focused on enhancing the ear's natural ability to pick up sound.
The external shape of the human ear is no biological accident. If there are no deformations to the pinna, the ears funnel sound into our ear canals, for processing by the eardrum, ossicles, auditory nerves, etc.
Most early hearing aids - the ear trumpet is the best known - worked to focus sound and direct it straight into the ear canal, while simultaneously blocking other noises. These are basically just a giant funnel that directs sound into the ear. For some forms of deafness, this might be effective - but only to a point. Profoundly deaf people cannot benefit from these because the sound cannot be amplified by the shape of the ear trumpet. Indeed, the decibel gain from these is so little, that they're really only suitable for mild to moderate hearing loss.
Another type of hearing aid from this time is the acoustic fan. Positioned behind the ear, it was also meant to funnel sound, but operated on a different principle than the ear trumpet.
For those with conductive hearing loss, bone conduction hearing aids came in the form of thin sheets held between the teeth. These were actually far more effective, as the principles of bone conduction made for greater decibel gain.
Here's a couple of quick references:
http://beckerexhibits.wustl.edu/did/19thcent/index.htm https://www.audicus.com/hearing-aid-timeline-visual-history/