A Portfolio of Illustrations:
The Progress of Hearing Aids


These illustrations were drawn by Frank L. Vanni, Visual Information Specialist of the Scientific and Technical Publications Section. Mr. Vanni followed several sources, particularly Kenneth W. Berger's 1970 classic The Hearing Aid: Its Operation and Development.

 

One

  Hearing enhancement is as old as cupping a hand behind an ear, a method that provides some 10 dB of gain in the region of 1000 Hz, is easy to use, and costs nothing. It is supposed that seashells and horns have been in use since time out of mind to extend sound gathering still further. Horn, in particular, is easily shaped and worked by heating and scraping; it was as generally useful to societies of antiquity as plastics are to ours. This drawing of a multisegmented hearing trumpet faced Chapter One.

trumpet Multisegmented Hearing Trumpet, circa 1670. Building up the device from separate pieces facilitated shaping it to direct sound from the user's front into his or her "good" ear.

 

Two

  Hand-held trumpets tended to deprive the user of the use of one hand as the price for improved hearing. Here a conical trumpet is attached to spectacle frames in an attempt to solve this problem. This drawing faced Chapter Two (1).

Spectacle Spectacle Trumpet. In order to give the user some comfort, the material of the cone would have to have been very light indeed.

 

Three

  Space did not permit the inclusion of this lovely binaural acoustic device that left the hands free while providing amplification; otherwise, it would have faced Chapter Three (2).

Ear Scoops Ear Scoops. These probably provided better directionality with less ambient noise from handling than most of the other acoustic designs.

 

Four

  One problem with acoustical instruments was that amplification is dependent upon size: the larger the trumpet, the more sound it could gather. The problem of concealing such devices prompted some ingenious solutions. Here, the entire table is the aid: sound is gathered through grillework in the neck of the "urn". It is directed down through the urn's body into the pedestal of the table, where it enters the ear tube. This Acoustic Urn faced Chapter Four (3).

Acoustic Urn The Acoustic Urn. Flowers placed in an insert add some realism to the camoflage.

 

Five

  At the opposite pole from concealment is flaunting what you have. The London Dome was a compound trumpet; its "stem" is actually part of an inner horn that faces the base of the outer shell, achieving the effect of a longer device in a compressed form. Made of brass or even silver, handsomely engraved examples exist that were obviously made to be admired. This one faced Chapter Five (4).

London Dome London Dome. Rather like a saxophone inserted into a kettledrum, the dome achieved considerable amplification in a small compass.

 

Six

  Electronics, particularly the transistor, made concealment of aids practical and affordable. Here a binaural aid dating from the 70s encloses all circuitry, including microphones and batteries, in the frames of eyeglasses. Only the earmoulds are exposed in this illustration facing Chapter Six (5).

Glasses Eyeglass Aids. Heavy plastic rims facilitate this modification by providing room for components.

 

Seven

  Largely concealed beneath the pinna, the behind-the-ear (BTE) aid remains the device of choice for some users, particularly those needing directional microphones or having difficulty manipulating smaller instruments. This example faced Chapter Seven

BTE Behind-The-Ear Aid. With sufficient size to more than accomodate today's smaller circuitry and batteries, the BTE's larger controls are convenient for those users with manipulation problems in addition to hearing difficulties.

 

Eight

  Miniaturization of components, including batteries, means that the auditory channel can house the entire aid. This completely-in-channel aid is scarcely noticeable and effective, providing sound unobtrusively to many users. This illustration faced Appendix 1 of Chapter Eight (6).

CIC CIC Aid. The small size of the aid, while cosmetically desirable, has the downside of making the controls difficult to operate by persons with arthritis or other manual impairments.

 

Nine

  Further minaturization of circuitry permits the direct stimulation of cochlea without the danger of infection: sound signals pass the skin barrier via magnetism, rather than via percutaneous wires. This schematic representation of the process faced Chapter Nine (7).

Cochlear Implant Cochlear Implant. Current induced within the implanted component stimulates the auditory nerves directly, bypassing damage to the cochlear structures.

 

Ten

  In a glance back at the 19th Century, this illustration of Giovanni Paladino's "Fonifero" of 1876 faced Chapter Ten. Essentially a rod with a smooth fork on the "transmitting" end and a cup on the "receiving" end, the Fonifero relied on bone conduction of sound to work, in addition to taking its signal from direct contact with the larynx region of the speaker. The cup was placed on the forehead, the mastoid area, or against the teeth of the listener (8).

Fonifero Fonifero. While cumbersome, this device bypassed both the mouth and the ear to benefit certain hearing problems.

 

Glossary

  And finally, this metal hearing trumpet faced the Glossary at the end of the book.

Ear Trumpet Ear Trumpet. The 18th Century technological advance of handling thin sheet metal for musical instruments made such hearing devices as this more affordable.

 
REFERENCES
  1. Berger KW. The hearing aid: its operation and development. Detroit, MI: The National Hearing Aid Society; 1970. p. 8.
  2. ibid., p. 12.
  3. ibid., p. 14.
  4. ibid., p. 10.
  5. Pollack MC. Amplification for the hearing-impaired. New York: Grune & Stratton; 1975. p. 269.
  6. Bess FH, Humes LE. Audiology: the fundamentals. Baltimore: Williams & Wilkins; 1990. p. 182.
  7. ibid., p. 195.
  8. Pollack, p. 5.
 
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Last revised Thu 02/11/1999