The (Really Cool) History of Hearing Aids

Evidence of hearing loss dates back to at least 10 000 years ago with archaeological investigations uncovering human remains with auditory exostoses, bony growths in the ear canal that may cause hearing impairment. The earliest written record of hearing loss was found in ancient Egypt where a manuscript dated to 1550BC, named the Ebers Papyrus, suggested a treatment for “ear that hears badly” involving a concoction of ant eggs, bat wings, goat urine, olive oil, and red lead injected into the ear canal. In 100AD a Greek physician was recorded as offering a cure for deafness by way of blowing a trumpet into the patient’s ear.

Thankfully, hearing loss remedies have progressed significantly since the days of animal parts and waste products. Ancient Roman history from 100AD recorded the use of a cupped hand behind an ear to improve hearing.

 
Ear Trumpets
From there, in the 13th century, humankind discovered that hollowed animal horns (it took us a little while to get past the age of using animal parts, apparently) were able to amplify and direct sound when the tapered end of the horn was held to the ear. From the late 1700s into the 1800s, a hearing device known as an ear trumpet was developed. Similar to a tapered animal horn, the ear trumpet captured sound at its flared end then compressed and amplified the sound into the listener’s ear via the tapered tube. Original ear trumpets were quite large and bulky, making them unattractive from both a practical and cosmetic viewpoint. As the 19th century progressed, ear trumpets went through several modifications, including changes to the size of the flared bell, the shape and orientation of the tube, designing the tube to be collapsible for ease of transport, and even disguising one ear trumpet model as a sneaky walking stick.

 
Carbon Transmitters
Hearing aid technology made a great leap forward at the end of the 19th century with the invention of electricity and carbon transmitters, allowing greater amplification of sound than previously possible with the ear trumpet. The earliest carbon hearing aids were about the size of a lunchbox and required a 3 to 4.5-volt battery. Initially the size of these hearing aids required them to be sat upon a table for use but by around 1930, these devices and their batteries had reduced in size enough to be worn around the neck or clipped to a shirt.

 
Vacuum Tubes
The integration of vacuum tubes into hearing aid technology allowed an increase in sound by as much as 70dB due to a better control of electricity flow when compared to the older carbon transmitters. In the early 1920s, vacuum-tube hearing aids became commercially available, but were large and heavy. A couple of decades later, these devices had become small enough to wear initially as a “two-piece” where the hearing aid could be clipped to the clothing while the batteries were either carried in a pocket or strapped to the leg, and later as a “one-piece”, with batteries small enough to be housed internally within the vacuum-tube aid. In this way, hearing aids apparently shared similarities with swimwear, including the development of one- and two-piece bathers which are becoming smaller and more difficult to see.

 
Transistors
The first transistor-controlled hearing aid was released at the end of 1952. The application of transistor technology allowed control of the volume of the current and paved the way for the hearing aid to shrink to a size that allowed it to be worn behind the ear (BTE) or in the ear (ITE). The size of hearing aids reduced even further once transistors became manufactured from silicon.

 
Digital Hearing Aids
In 1996 the first fully-digital hearing aid became commercially available. Up to this stage, the amplifier component of a hearing aid was analog, meaning all it could do was indiscriminately amplify noise. With the advent of a digital amplifier, the level of user-control over the sound environment was amplified, too. From automatically negating feedback to managing ambient noises, connecting wirelessly to a cell phone or reacting to music, digital hearing aids are an infinitely better option than ant eggs and goat urine.

Hearing aid technology continues to advance and we can expect to see them become smaller, more comfortable, and more adaptive to the sound environment. As medicine develops alongside, perhaps one day we’ll even see hearing aids become redundant as new hearing loss treatments emerge.

 

 
References
No longer deaf to the past. https://www.historytoday.com/no-longer-deaf-past
The hearing aids of yesteryear. https://www.hearingaidmuseum.com/resources/The%20Hearing%20Aids%20of%20Yesteryear.pdf
The digital hearing aid difference. https://www.starkey.com/blog/2018/05/Digital-hearing-aids
Hearing aid history: from ear trumpets to digital technology. https://www.healthyhearing.com/report/47717-Digital-hearing-aid-history