People have had hearing loss for all of recorded history. Birth defects, trauma to the ear, or a burst of incredibly loud sound can all lead to problems hearing. Since man began to shout to communicate over long distances, like chimpanzees in the wild, and especially since the industrial revolution, hearing loss has become more likely over time. The advent of MP3 players, the spectacle of live concerts, machines pounding away in factories, and jackhammers blasting the pavement have all increased the likelihood that one day many of us will need hearing aids. Just as the causes of hearing loss have changed and multiplied, hearing aids have gone from the natural to the scientific and surgical. This is Part 1 of a 2 Part History of Hearing Aids.
1. The Cupped Hand
The history of hearing aids begins with natural aids to hearing like the cupped hand. The cupped hand reduces sound from behind the head (blocked by the back of the hand) and funnels sound into the ear canal. The person speaking to you can also be a natural aid to hearing if they are aware of some simple strategies to improve communication with the hearing impaired. One of the best strategies to keep in mind is to always face the speaker and speak clearly. Do not block your mouth with your hands or food. Allow the listener to “see” you speak.
2. Ear Trumpets
The aim of hearing aids is to increase the volume of sound for the impaired user. The only way to do this, before electricity, was to filter out other noise by directing the desired sound straight into the ear.
The first real development in hearing aid technology came in the form of external aids such as shells. Referred to as ear trumpets, shells essentially did the same as cupping your ear with your hand. Trumpets and cones are a little more advanced than a cupped hand or basic shell. The wide opening of the ear trumpet funnels sound from a wide area into a smaller and smaller tube eventually entering the ear.
A clever French design combined eyeglasses with a lightweight, dark tortoise shell ear trumpet meant to be more easily concealed by dark clothing. This sounds strange at first but when you remember that sound consists of waves, vibrations in the air, a cone-like structure makes a lot of sense for collecting and amplifying sound.
3. Conversation Tubes
Conversation tubes are typical flexible rubber tubes used for channeling sound much like the ear trumpet. The speaker talks into a trumpet-like device which is connected to the tube and up to three listening devices are attached to three other tubes. A heavy tabletop dish or bowl can be used to steady the four tubes.
Acoustic thrones were popular with European royal families in the 18th and 19th centuries. The acoustic chair was invented in 1706 which basically combined a modified chair with a conversation tube. Openings in the armrests, shaped like lion heads for royalty, hid resonators which caught the speaker's voice and funneled the sound waves through a tube to an earpiece used by the royal family member.
The Stethoclare (1914) was a portable sound-catcher to be placed on the table and hooked up to a tube that would run from it to the user's ear. There were earlier more cumbersome versions of this type of device that had to be placed on tables in the household and disguised by flowers and fruit. Often people would place fruit inside the device which would dampen the resonating effect.
4. Bone Conduction
The above methods only help with hearing problems if both the outer and middle ear are functioning, although most likely at a reduced level. In 1580 a scientist introduced the idea of improving hearing with sound wave conduction through the teeth. Remember, teeth are actually bones. In 1757 another scientist came up with a bizarre idea which entails a deaf person holding one end of a wooden rod between his teeth while the speaker holds the other end between his teeth. This was a literal example of the theoretical idea introduced almost 200 years before.
The famous composer Ludwig van Beethoven was deaf but found he could hear the music emenating from his piano when he placed one end of a wooden rod against his piano and the other end either between his teeth (as in the proposed solutions from the scientists) or against the side of his head (the skull being quite a large bone). In 1876 a man by the name of Giovanni Paledino advertised the first bone conduction hearing aid. What Giovanni published was basically a diagram with two figures and the metallic device between them, but the 'Fonifero' connected the listener's cranium directly to the speaker's larynx providing the most direct amplification without having the hearing impaired individual's skull pressing up against the throat of the speaker.
The 'Audiphone' in 1879 was a large but thin, round wooden device to be held against the teeth. The wood was to be curved against the teeth and the tension held by a short piece of string, similar to a bow used for archery. Certain frequencies vibrated the wood and could be adjusted by shortening or lengthening the string which would relax or tense the wood.