The Evolution of Hearing Aids

The Evolution of Hearing Aids

the first electric hearing aid

bone conduction discovered

transistor hearing aid

earliest efforts to fix hearing

in 1700, bone conduction was discovered and lead to the next phase of amplification and hearing aid attempts.

the first recorded "hearing aids" were wood carvings of ears from animals with good hearing.

the first and most primitive attempt to increase hearing was cupping your hand behind your ear. it increases hearing 5 to 10 db

dentaphone: used bone conduction through the teeth up through the maxilla and the mastoid process to the inner ear apparatus

invented in 1880 by Thomas Graydon

• Alexander Graham Bell invented the telephone
• Thomas Edison invented the carbon transmitter amplify the telephone signal (15 dB) in 1870
• Led to the development of Carbon Hearing Aids in 1902
• first hearing aid with volume control
• Worn around the neck
• increased the sound by 25-30 dB
• Not ideal because of limited frequency range, tendency to produce scratchy sounds, heavy battery packs, low battery life

Analog to digital: hybrid digital-analog models: introduction of digital processing chips to hearing aids (1980s)

1996- first digital hearing aid

2000's: same circuitry used in cell phones and computers

amplify, reduce, filter, and direct sound as needed

fully customizable, programmable

soft amplification for home settings, targeted amplification of voices in restaurants, diminished wind noise on the golf course, etc

1948 - Bell Telephone Laboratories invented the transistor, a switch the regulates electrons and therefore electricity

transistors only need 1 battery

enabled smaller hearing aids to be worn inside ear

"body aid"

Late 20th Century: transistors made of of silicon (smaller)

bone conduction fans were invented and are small fan shaped devices placed behind the ear

Natural Magick, 1588 by Giovanni Battista Porta

1800

1500-1600

1900

2000

1300

vacuum tube hearing aids

hearing aids in disguise

ear trumpets

in the 1800's hearing trumpets and conversation tubes evolved into decorative pieces hidden into accessories

• started in 1920s
• able to increase sound by as much as 70 dB
• this was achieved because the vacuum tubes regulated the flow of electricity better
• also started out large and inconvenient
• eventually decreased in size
• amplified all sounds not just the ones the user wanted to hear

table top vactuphone

• the 18th century updated this idea with the more modern ear trumpet
• same concept made with common metals like brass or copper
• can amplify the sound by 10 to 20 dB
• doesn't help the speech ranges much

• Wide at one end and narrow at the other
• Used to funnel sound into the ear
• Hollowed out animal horns were made of cow or ram horn
• also made from seas shells or glass
• 13th century to the 18th century

Opera glasses- the handle funneled sounds to the ear

The first type were called Aurolese phones made by F.C. Rein

Beard receptacle - funneled sounds from front

later model (1950)

Acoustic Chairs

this chair was crafted by F.C. Rein for King John the VI of Portugal

the lions mouths direct the sound to the ear through hollow arms

popular with royalty

some chairs were discreet and had a hearing tube snaked through the armrest and around the back to the user's ear

others incorporated ordinary hearing trumpets within the design of the chair with no effort towards concealment