Hearing aid history: From ear trumpets to digital technologyHearing aid history: From ear trumpets to digital technology
It is said that time marches on and one thing is certain: hearing loss marches right along with it. The recorded history of hearing loss goes back hundreds of years, and attempts to correct hearing loss have been in existence since the very first person to cup their hand behind their ear.
The good news is hearing aids and other assistive listening devices have come a long way since the first rudimentary attempts at improving hearing. Yes, hearing aid technology is still evolving and is far from perfect, but looking back through the years of technological advances certainly allows us to put any complaints about modern hearing aid technology in clear perspective.
13th century to 19th century: From animal horns to ear trumpets
As early as the 13th century, those with hearing loss were using hollowed out horns of animals such as cows and rams as primitive hearing devices. It wasn’t until the 18th century that the more “modern” ear trumpet was invented. Funnel-shaped in design, ear trumpets were man's first attempt at inventing a device for treating hearing loss. They didn’t amplify sound, however, but worked by collecting sound and “funneling” it through a narrow tube into the ear.
Cartoon-like and bulky, these ear trumpets and the subsequent speaking tubes didn’t work all that well. But it didn’t prevent them from remaining the only option until electricity and the telephone were invented in the 19th century.
19th century to 20th century: The first electronic hearing aids
The invention of the telephone combined with the practical application of electricity in the 19th century had a tremendous impact effect on the development of hearing aids and other assistive hearing devices. People with hearing loss quickly realized they could hear a conversation better through the telephone receiver held up to their ear than they could in person. However, Thomas Edison, who experienced hearing loss firsthand, saw room for improvement. In 1870 he invented a carbon transmitter for the telephone which amplified the electrical signal and increased the decibel level by about 15 decibels (dB). Although an amplification of about 30 dB is usually necessary to allow those with hearing loss to hear better, the invention of the carbon transmitter for the telephone paved the way for the technology that would eventually be used for carbon hearing aids. Although not ideal due to their limited frequency range and tendency to produce scratchy sound, carbon hearing aids were in use from 1902 until the advent of the next wave of technology: vacuum tube hearing aids.
1921-1952: Vacuum tube technology
Beginning in the 1920s, hearing aids using vacuum tubes were able to increase the sound level by as much as 70 dB. These sound levels were achieved because vacuum tubes controlled the flow of electricity better than carbon. The problem was the size. In the beginning the devices were very large, about the size of a filing cabinet, so they were not portable. By 1924 the size of vacuum tube hearing aids had been reduced so all of the components could fit in a small wooden box, with a receiver that the user held up to the ear. Despite the improvement they were still heavy, bulky and conspicuous, and amplified all sound, not just the sounds the user wanted to hear.
Improvements in technology continued in 1938 when Aurex introduced the first truly wearable hearing aids, consisting of an earpiece, wire and receiver that could be clipped to the user’s clothing. Unfortunately, this model also required the use of a battery pack that was strapped to the user’s leg.
Thanks to technology developed during World War II, the late 1940s finally saw the production of hearing aids with circuit boards and button-sized batteries, allowing the batteries, amplifier and microphone to be combined into one portable, pocket-sized unit. Even though they were marketed as discreet, the pocket unit connected to individual earpieces with wires that made them less than appealing from a cosmetic standpoint.
Despite the advances in technology, the world still waited for small, one-piece hearing aids that could fit entirely in the ear and truly be worn discreetly. Fortunately, they didn’t have to wait long.
Mid-20th century: Transistor technology
The move to smaller, more discreet hearing aids finally got underway in 1948, when Bell Telephone Laboratories invented the transistor. A transistor is a switch that controls the movement of electrons and thus electricity. Transistors can start and stop the flow of a current and also control the volume of a current, making it possible to have multiple settings in one device. Norman Krim, an engineer at Raytheon, the inventor of the previous sub-miniature vacuum tube technology, saw the potential application for transistors in hearing aids. By 1952, Krim was able to create junction transistors for hearing aid companies. The transistor technology not only enabled hearing aids to be made smaller, they could finally be worn either completely inside or behind the ear. The new hearing aids were so popular and successful that over 200,000 transistor hearing aids were sold in 1953 alone, eclipsing the sale of vacuum tube hearing aids.
Capitalizing on the new technology, one of the first hearing aids to be worn almost entirely in the ear was invented in the late 1950s by Otarion Electronics. Called the Otarion Listener, the electronics were embedded in the temple pieces of eyeglasses. These “hearing glasses” caught on and versions of the technology were soon introduced by other companies such as Beltone and Sonotone.
Late 20th century: Analog to digital
Eventually, hearing aid manufacturers developed the ability to make the transistors out of silicon, enabling hearing aids to shrink even further. Hearing aid technology closer to that which we know today was introduced by Zenith Radio in the 1960s; in these versions, the microphone went in the ear and was connected by a small wire to an amplifier and battery unit that was clipped to the ear. This technology stayed largely the same until the 1980s, upon the introduction of digital signal processing chips to hearing aids. The first to use the technology created hybrid digital-analog models (digital circuits controlling an analog compression amplifier) until 1996, when the first fully digital hearing aid model was introduced.
21st century: High tech and new horizons
By the year 2000, hearing aids had the ability to be programmed, allowing for user customization, flexibility and fine tuning, and by 2005 digital hearing aids represented about 80 percent of the hearing aid market. Digital technology is the same circuitry that is used in cell phones and computers. Today’s hearing aids can be fine-tuned by a hearing care professional and customized to an individual’s hearing needs. They can adapt to different listening environments and be connected to other high-tech devices such as computers, televisions and telephones. Features such as telecoils, Bluetooth and FM connectivity allow compatibility with other electronic devices and accessibility in public spaces.
Yes, we’ve come a long way from the days of ear trumpets, and hearing aids continue to evolve as technology advances. On the market today are products with a truly rechargeable hearing aid battery. Many hearing aids are “smart,” adapting to different listening situations without the intervention of the user. Long-wearing hearing aids, which can stay in the wearer’s ear canals for several weeks, have been available for several years. Certainly in the future, hearing aids will continue to increase in performance and comfort while decreasing in size.
Be sure to see a hearing care professional in your area to check out the latest updates in hearing technology and find out which device is right for you.