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History of Hearing Instruments

ODHHS Information and Technical Assistance Series
 
 

Essential Highlights in the
History of Hearing Instruments
 
 
 
Centuries ago, if people were hard of hearing their only option was to exercise a little self-help - they simply cupped one of their hands behind the weak ear in order to amplify the sound.
 
Certainly, in literature, it is difficult to find the first mention of a hearing aid, but one of the first references is from 1650, when Athanasius Kircher from Rome published a two-volume work in Latin. The German title is: "Neue Hall und Thonkunst". In this work Anthanasius mentions and illustrates several hearing aids, which were tubes, fans and horns.
 
In the 19th century it becomes easier to track the history of hearing instruments:

 
In about 1800, in London, F.C.Rein establishes itself as the first company to manufacture hearing aids on a commercial basis. The company manufactures hundreds of different hearing aids, most of which are tubes and trumpets in limited numbers.

 
The first patent for an electrical hearing aid is filed in 1892 by Mr. Alonzo E. Miltimore (patent no. 466,725). Other patents follow, but none of these ever reach production. The first hearing aid produced - an earphone connected to a carbon microphone fastened on a battery box - is the innovation of Dr. Ferdinand Alt of the Pilitzer Clinic in Vienna. This was probably only produced in one example.
 
During this time, Alexander Graham Bell has also been mentioned as the person who built the first earphone for amplifying sound for the hearing impaired. To our knowledge, he never filed a patent for what was possibly the "first hearing aid".

 
Bertram Thornton builds a simple telephone arrangement at the Margate Deaf and Dumb Asylum in England. He obtains a British patent (No. 18,780), but this equipment is probably also produced only once.

 
This is when the first commercially manufactured hearing aid becomes available. Called "Akoulallion", it is produced by Akouphone Co. of Alabama in the US. This table-model instrument is made of carbon, and costs $400. In 1900 this instrument is remodeled and re-named "Akouphone".

 
At this stage microphones are being made of carbon dust, but this does not perform well. Then comes a new development - the carbon ball - which is invented by Hutchison and Kelley. This invention increases the quality and reliability of electrical hearing aids. The carbon ball is used in the hearing aid fitted to the English Queen Alexandra for her coronation in 1902.

 
At this stage, the efficiency of the electrical carbon hearing aid is governed by the relationship between the size of the microphone and the earphone. The bigger the microphone compared to the earphone, the more amplification is achieved. Carbon instruments are produced with a "small-sized" microphone for mild hearing losses - like the Acousticon SRB. For moderate hearing losses, the Acousticon SRD has a double-sized microphone. And for severe hearing losses, a quadruple-size microphone is incorporated into the Acousticon Massacon model.

 
The triode vacuum tube or valve is invented in 1907 by Lee DeForest, and is quickly adapted for radio applications. But it is Earl C. Hanson who takes credit for the first vacuum tube hearing aid, which is patented in 1921 and manufactured by a company called Globe. Equipped with a single triode, this instrument is a little bigger than an early camera box.

 
The Bone Conductor, or BC, is invented by Hugo Lieber and used in hearing aids from 1933 onwards. When placed on the cranium, the BC acts a vibrator which transmits the sound directly to the inner ear. It is used for all types of hearing losses, but is most effective in assisting people with middle ear diseases.

 
The first vacuum tube hearing aid is designed by two manufacturing companies located in England - Amplivox and Multitone. This kind of device needs two batteries in order to operate, and is limited by the lifetime of the batteries, which is often only one day!! Produced by companies such as Acousticon, Maico, Radioear, Telex, and Western Electric, it consists of four elements: a microphone, earphone/receiver, amplifier and two batteries.

 
The development of smaller batteries, and advances in vacuum tube technology result in Beltone's introduction of the first one piece vacuum tube hearing aid. This rapidly becomes the standard for the design of new hearing instruments.

 
Up until now, hearing instruments are only worn on the body. They are heavy and expensive to use due to high battery consumption. But all this changes in December 1947, when the transistor is invented at Bell Laboratories in the US. This proves to be a fantastic invention, also for hearing instruments. It is small, cheap and effective, and has a very low battery consumption compared to vacuum tube instruments.

 
In 1952 Raytheon Manufacturing Corp. introduces "the junction transistor". Due to its enhanced data, this transistor is very suitable for hearing aid constructions. In 1953 Microtone, Maico (a member of the William Demant Group), Unex and Radioear introduce their first transistorized hearing aids.
 
The original models are worn on the body, but shortly after they are replaced by head worn models or barette devices, which are often attached to the hair by a clip. Barettes are quickly designed to fit behind or over the ear. Some of the first companies to introduce behind-the-ear (BTE) instruments are Tonemaster, Qualitone, Auditone, Sears, Zenith and Beltone.

 
In 1954, A US-based company called Ontarion introduces "The Listener" - a hearing aid built into spectacles using transistors.

 
At this stage, it is impossible to identify the first in-the-ear (ITE) hearing aid because many manufacturers work simultaneously on projects to develop a small ITE instrument. Due to their size and shape, most of the first ITEs are often referred to as "at-the-ear" (ATE) instruments, because they are attached to an ear mold and protrude outside the ear.
 
In June 1955, Dahlberg Co. in the US introduces the Miracle Ear, which is their first ITE instrument. In late 1957 or early 1958 a hearing aid dealer by the name of Leslie P. Leale from California builds a custom ITE for one of his clients. This signifies the birth of a model called Ear-Master, which is then manufactured by Earmaster Inc.

 
Hearing instruments which only fill the ear canal - known as "in-the-canal" (ITC) instruments - become a reality only after a small 312-size battery is developed. Two such instruments are the Unex model IE, manufactured by Nichols & Clark, and the Miracle Ear III from Dahlberg Co. Neither of them require an ear mold, and both use the 312 battery. They closely resemble the modular ITC we have today.

 
In the 'sixties hearing instruments become smaller and more reliable. BTEs get so slim that they almost fit behind the auricle. ITEs get smaller too. The ITC models are not so popular, since their quality and reliability are too poor. Body-worn devices account for less than 10% of the market. The first BTE featuring an integrated circuit is marketed by Zenith.

 
In 1969 the first hearing aid which utilizes a built-in directional microphone is manufactured by Willco (W. Germany). Oho Hassler of Willco receives a US patent (No. 3,662,124) on a directional microphone.

 
A company called Linear Technology (now Gennum Corp.) introduces the first integrated circuit made for hearing instruments with compression. G. Donald Causey, PhD, and Daniel Graupe, PhD, design a prototype hearing aid which incorporates special circuitry "to remove environmental noises from speech". This is later to become known as the "Zeta Noise Blocker".

 
In the 1980s IC technology is being further developed. Many new circuits which utilize analogue sound processing - such as Manhattan I-II and Etymotic Research K-AMP - are marketed at this time.

 
Nunley, Staab, Steadman, Wechsler and Spencer report on a potentially wearable digital hearing instrument which has been developed at Audiotone in 1983. In the digital hearing aid, the instrument itself contains digital circuits similar to those in a computer, for processing sound.

 
The University of Wisconsin and Nicolet Instrument Corp. launch a project which results the first truly digital body-worn hearing aid: the Phoenix.

 
The Phoenix digital hearing instrument is introduced by Nicolet in 1987. It is wire-connected to a BTE, and is later developed only as a BTE version driven by two 675 type batteries. Only three prototypes are made of this product. As a hearing aid company, Nicolet no longer exists.

 
In the US, Mead Killion reports on a completely-in-the-canal (CIC) instrument.

 
In the late 1980s, many programmable hearing aids are introduced. Using conventional analogue circuitry, they can be programmed electronically from a specially designed computer and software. With the PHOX system, Bernafon/Maico become the first to introduce a programmable instrument. Then Widex (DK) introduces the Quattro system - featuring a user-operated remote control which also can be used to program the instrument. Products like Auditone 2000, 3M Memory Mate, Sound Selector from Ensoniq, and Resound Personal Hearing System are among the other programmable hearing instruments on the market.

 
Oticon introduces the E43, which is especially developed for people who suffer from noise-induced hearing losses.

 
Danavox presents a new solution for suppression of feedback in hearing instruments. Using digital technology, the system is called Digital Feedback Suppression. The DFS system is introduced in a power BTE model called Genius.

 
Oticon in Denmark presents the first fully automatic hearing aid without a volume control. Called MultiFocus, it has two channel non-linear sound processing.

 
Maico (US) presents a programmable CIC called the RD301, with two programs and volume control. The RD301 is controlled by a remote control.

 
Oticon introduces the JUMP-1 digital hearing aid platform which is based on the Digital Audio Processor (DAP). This platform provides all the state-of-the-art features of conventional instruments. JUMP-1 instruments are offered to 14 different audiological research centers worldwide, in order for them to utilize the digital platform in the development of new, innovative solutions for the hearing impaired.

 
Oticon launches DigiFocus - a 100% digital BTE hearing instrument. This is based on a new audiological rationale called Adaptive Speech Alignment, which splits sounds in seven tone bands and utilizes two different speech processors - one for vowels and one for consonants.
 
Widex then introduces Senso, the world's first digital in-the-ear hearing aid.

 
Oticon introduces "The New Generation DigiFocus" including a fully automatic canal version of DigiFocus. The new chip-set with improved performance allows for a 3-step acclimatization program, advanced feedback management and in-situ assessment of the client's most comfortable listening range.
 
Meanwhile, Widex introduces the Senso CIC, which is the first fully digital CIC instrument.
 
Philips demonstrates its own digital instrument - the D72 - which uses a remote control and SMART cards to store the instrument's different user programs.