CARBON-TYPE ELECTRICAL HEARING AIDS: BULKY BUT BETTER
The introduction of the carbon-type hearing aid in the early 1900s marked the evolution from mechanical to electrical means for amplifying sounds. Through the use of external electrical power (batteries or alternating current [AC]) hearing aids could increase sound levels (i.e., apply gains) far greater than what was possible with purely mechanical hearing devices.
The carbon hearing aid, based on the technology of the telephone, had four separate components: 1) an external power source; 2) a carbon microphone (which transduces the acoustic signal to an electrical one); 3) an amplifier/volume control; and 4) an electro-magnetic receiver (i.e., a tiny speaker that transduces the electrical signal to an acoustic one). Although these carbon-type hearing devices could provide more gain than mechanical ones, they were also neither convenient nor user-friendly. They were bulky, required a warm-up period, and often had unstable performance. The batteries had a limited service time, and the long, multiple cords tangled easily. A typical table-top model of this era, the Acousticon Model 56 from 1928, is shown in Figure 1 with the four separate components labeled.
A trend for hearing devices to be designed for camouflage or concealment, as mentioned in the second installment of this series, started in the 19th century when hearing aids were purely mechanical. Such designs appealed to users’ vanity and their sense of aesthetics. Despite the substantial size of carbon-type hearing aids, concealment was still desirable and possible. Some carbon-type hearing aids were designed to look like radios, cameras, or purses of the era.
VACUUM TUBE-TYPE ELECTRICAL HEARING AIDS
Hearing devices first became wearable in the 1930s, thanks to technological advances in batteries and the invention of the vacuum tube.1 The vacuum tube, especially, enabled monumental changes. Compared with amplifiers in carbon-type hearing aids, vacuum tube circuits were much smaller and consumed much less electrical power, which in turn enabled savings in battery size. Consequently, hearing aids could be designed with the amplifier and microphone combined into a single unit, while the battery and receiver remained separate units connected by wires to the combined unit. Vacuum tubes were, however, fragile (mostly glass) instruments, and their operation was detrimentally affected by humidity and overheating. Additionally, the batteries for vacuum tube-type hearing aids were still rather large and weighed about 2.5 pounds. Figure 2 shows the separate units of a 1950s-era hearing aid worn by a young boy.
As ever, hearing aid manufacturers created designs aimed at concealment and cosmetic appeal. The still somewhat bulky battery pack was generally worn under clothing or fit into a user's pocket. For women especially, batteries were worn in special harnesses within undergarments. A Sonotone advertisement from the 1940s advised women that the large batteries could be worn using a battery garment “under the arm, beneath the bust, or on the leg.”2
TRANSISTOR-TYPE ELECTRICAL HEARING AIDS
Continued advancements in battery technology and the invention of the electronic transistor in 1947 allowed for the miniaturization of hearing devices. The microphone, amplifier, and batteries could be consolidated into a single unit with a cord to the receiver or earpiece. Compared with vacuum tubes, transistors, made of various semiconductor materials, were not only much smaller but also less fragile, more reliable, and could amplify signals with improved fidelity.
Due to the substantial reduction in overall size and the combination of separate units, many ingenious designs of hearing devices that appealed to the vanity of hearing aid users flourished during the mid-20th century. Women's hairstyles provided a means for concealing hearing aids (sans the receiver unit) into barrettes and combs. One brochure from the Paravox Corporation for their Veri-Small hearing aid outlined every step needed to create a “secret hair-do” for “ideal hidden hearing.”3 Wigs, hats, and scarves were also cleverly designed to hide hearing aids. Women's jewelry provided yet another avenue for concealing hearing aids; hearing aid cords became pearl or beaded necklaces, ear-receivers were disguised as earrings, and microphones were made into pins or pendants. Maico touted the Whisper-Lite Hear-Rings in 1960 as an “amazing new fashion accessory… because they glamorously conceal any hearing correction.”4
Appeals to men's vanity was equally strong in the marketing of hearing aids. Men could hide their hearing aid inside a shirt pocket, or wear one disguised as a tie clip. One ingenious design, introduced by the Telex Corporation in 1950, was the Telex 300 fountain pen. The pen, which incorporated all the hearing aid components except the receiver, could be worn in one's pocket with the receiver cord cleverly hidden under a shirt. An advertisement noted the Telex 300 as a precedent-shattering model to “help keep your hearing loss a secret from all the world.”5 Another concealed hearing aid targeted at men was the Acousticon Wrist-Ear produced around 1955, advertised as a “revolutionary new accessory” to wear like a wristwatch. The cord leading to the receiver was concealed under a sleeve.6
For both men and women, a very popular and concealed design model was the eyeglass hearing aid, introduced in 1954. Five years later, in 1959, eyeglass hearing aids represented 50 percent of all hearing aid sales.7 First Lady Eleanor Roosevelt was featured in advertisements for eyeglass hearing aids and was quoted: “If people only knew what a revelation and a joy the Listener is, they would not hesitate to wear one. This is the first hearing aid that exactly fits my needs. I didn't realize a hearing aid could be as good as this.”8 Concealed-design hearing aids were popular, and the names of the models fit perfectly with the 1950s Cold War atmosphere. Sample model names were “Top Secret,” “Privat-Ear,” “Top Secrette,” “Invisible Ear,” “Unseen Ear,” and “Hide-A-Way.”9
Celebrities were also used to promote hearing aids. Bob Hope and Mary Pickford were among those who touted the use of hearing aids. An internal memo from Paravox from the 1950s explicitly stated their marketing rationale for the use of celebrities:
“… it is a step forward in a program to arouse a realization in the hard of hearing people that other people are interested in their problems. If, for example, a hard of hearing person reads that Bob Hope or Mary Pickford have a favorable opinion of hearing aids, isn't it possible that his or her reluctance to wear an aid may be reduced?”10
GOING, GOING, NEARLY GONE
Further advancements in electronic technology, particularly the introduction of integrated circuits and eventually computer chips, again influenced the design of hearing aids. Around 1965, the four basic components of hearing aids (battery [power source], microphone, amplifier, and receiver) could be combined into a single sleek, powerful, and virtually unnoticeable unit worn on the ear. Soon, people with hearing loss had a myriad of choices for hearing aid styles: behind-the-ear (BTE), in-the-ear (ITE), in-the-canal (ITC), and completely-in-canal (CIC) hearing aids. All these varieties could be concealed easily even while possessing components powerful enough for those with severe and profound hearing loss. Another major advancement around this period, unrelated to electronic components, was the development of custom earmolds. The older one-size-fits-all ear-level receivers contributed to hearing aids’ deficiencies in providing gains for high-frequency sounds. By contrast, snugly fit custom earmolds reduced acoustic feedback loops and allowed for greater high-frequency gains.
Although concealment of hearing aids is still desired by many, societal attitudes toward disabilities are changing. In 1983, U.S. President Ronald Reagan was fit with a Starkey INTRA hearing aid.11 After Reagan was pictured wearing his aid, hearing aid sales increased substantially and public acceptance of hearing aids may have also increased.12 Manufacturers of hearing devices share common goals—to produce hearing devices that provide listening benefit while also being artistically pleasing and are as small as possible. In that sense, little has changed over the years. The marketing of hearing devices focuses on the devices’ appeal to potential users. The latest advances in electronic and digital technologies enable hearing devices to be concealed easily, yet capable of large acoustic gains. Today's hearing aid users have the best of both worlds; it is no longer necessary for users to sacrifice hearing aid performance over vanity.
1. Berger K. “History and Development of Hearing Aids.” In Polllack M., ed. Amplification for the Hearing Impaired. 3rd ed. New York : Grune and Stratton; 1988.
4. Advertisement: Whisper-Lite Maico. Vogue. (March 6, 1960): 58.
6. Advertisement: Acousticon Wrist Ear. Daily News. (Monday June 6, 1949): 10.
7. Lybarger S, Lybarger E. “A Historical Overview.” In: Sandlin RE, ed. The Textbook of Hearing Aid Amplification. 2nd ed. San Diego, CA : Singular Publishing; 2000.
8. Advertisement: The Listener. New York Times. (May 21, 1957): 79.
9. Berger K. The Hearing Aid : Its Operation and Development, 3rd edition. Livonia, MI : National Hearing Aid Society, 1984.
11. Weisman SR. Reagan begins to wear a hearing aid in public. New York Times. (September 8, 1983):14.
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12. Gerling I, Taylor M. Quest for quality and consumer appeal shaped history of the hearing aid. The Hearing J. 1997;50(11), 39-44.