From cupped hands to a futuristic device that uses light beams to transfer sound, hearing technology has evolved dramatically over the past couple millenia or so.
This evolution can be broken down into five different eras: acoustic, carbon, vacuum tube, transistor and microelectric/digital.
THE ACOUSTIC ERA
- 117-135 A.D.
- Cupping a hand behind the ear to collect sound into the pinna: This increased amplification within the range of 1,000 to 3,000 hertz (Hz).
- Using animal horns to funnel sound into the ear: This increased amplification within the range of 250 to 2,000 Hz. (Different horns would provide amplification at various frequencies.)
- Inserting the smaller opening of recently invented, man-made trumpets into the ear canal: This increased amplification within the range of 250 to 3,000 Hz and provided a gain of up to 30 dB.
THE CARBON ERA
- Francis Blake and David Edward Hughes developed the carbon transmitter.
- Miller Reese Hutchinson invented the first wearable, practical and commercially available hearing aid, which included a carbon microphone, a magnetic receiver, connecting cords and a battery.
- Sonotone corporation introduced the first bone-conduction hearing aid, which included an oscillator attached to a headband placed on the mastoid.
THE VACUUM TUBE ERA
In the late 1930s, the first body-worn hearing aids were introduced. These bulky devices used a vacuum tube and a carbon or crystal microphone. They allowed a wider frequency range – up to 4000 Hz – and more amplification.
THE TRANSISTOR ERA
This was the turning point for hearing aids as the devices became much smaller and more convenient. During this time, eyeglass hearing aids, behind-the-ear hearing aids and in-the-ear hearing aids entered the market.
THE MICROELECTRIC/DIGITAL ERA
In 1995, the first ear-level digital hearing aid became available. Up until this point, hearing aids were analog, but the rise of the digital era led to the hearing aids we know today – technologies as advanced as the Earlens.