Hearing Aids 1899 – From Ear Trumpets to Modern Devices

Devices that amplify sound to help people with hearing loss date back to antiquity, when hollow animal horns were held beside the ear to make sounds louder. 

• In his 1558 book Natural Magick, Italian scientist Giambattista della Porta described wooden hearing devices shaped like animal ears. 
• From the 1600s onwards, various funnel-shaped “ear trumpets” were used to direct sound into the ear. 
• In 1899, American inventor Miller Hutchison built one of the first electric hearing aids, consisting of several earpieces and using a carbon microphone. 

From the 1600s, a small “ear trumpet”. A huge two-horn system at Bolling Field in Washington, D.C. (1921).

Early “useful” electric hearing aids in the 1900s were impractical because of the large vacuum tubes needed to amplify sound. From the 1950s, transistors allowed devices to become smaller and more sophisticated, while providing more advanced sound-processing and transmission functions. Some hearing aids could even be built into spectacle frames. 

Many hearing-aid styles are available today. Behind-the-ear devices have a casing containing the amplification system behind the ear, with a tube running into the ear canal. Other devices fit entirely inside the ear canal. Bone-anchored hearing aids vibrate the skull and inner ear.

In general, hearing aids are devices for capturing sound (microphone), amplification and improving clarity. Modern hearing aids are highly sophisticated and may include noise-reduction circuits, programmability and selectable modes. They can use both omnidirectional and directional microphones, the latter being useful when communicating with a particular person. 

Inside a hearing aid is a “telecoil”, a small wire wound around a rod. It functions as an antenna, collecting magnetic signals and converting them into sound.

Description of the article image: A photograph of Swedish soldiers using an acoustic locator in 1940. Such devices were used to locate aircraft before radar became widespread.

Historical figures mentioned in the article: Giambattista della Porta (1535–1615), Thomas W. Graydon (1850–1900), Miller Reese Hutchison (1876–1944)

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