Who invented the hearing aid? Tough question...
Do you mean who invented the modern hearing aid? Or the first portable hearing aid? Or the first electrical hearing aid? Or perhaps the first device of any kind to help haring impaired?
I’ll try to answer...
I think I should point out two persons that many consider as the inventors of the hearing aid.
Considered by many as the inventor of the first electronic hearing aid. He stands behind two milestones in the history of the hearing aids.
Back in 1899, he established a firm named Akouphone (along with J Wilson). They invented the first electronic hearing aid (they named it Akoulathon). You have to place it on a table in order to use it and it was sold for about 400$. It was made of a carbon microphone, battery and ear set.
In 1901, Hutchison improved this invention and made the first wearable hearing aid. He called it Acousticon. It was built similar to the Akoulathon but was with reasonable size so you could carry it around on you.
Another inventor struggling to get the title of “the one who invented the hearing aid” was Harvey Fletcher. He was a physicist and worked for bell labs, investigating and developing all sort of devices and patents related to hearing. Around the twenties, he led the research that eventually led to the invention of the first hearing aid using a vacuum tube to amplify. A vacuum tube is a basic electrical circuit’s building block that enables you to amplify electrical signals. This milestone is the ancestor of all the hearing aids we know today.
As I mentioned above, the definition of who invented the hearing aid is not well defined. There where many steps along the way and there are steps and improvements that are taking place even today. The two gentlemen I mentioned are those who actually made the very basic hearing aids and therefore I think that this is as close as one can get to be credited as the inventor of the hearing aid.