The Evolution of Hearing Aid Technology:
Exploring the Radioear Collection
Over the past few centuries, assistive hearing technology has transformed dramatically, from ear trumpets to hearing aid tables to battery-powered devices that can be hidden in eyeglass frames. This project invites you to explore a timeline of hearing aid advancement, featuring devices from the Radioear Collection.
Radioear
​This digital exhibit highlights devices from Radioear Corporation, a Pittsburgh-based hearing aid company. This collection is not yet available to the public, but we encourage viewers to inquire about the collection at Pitt's Archives and Special Collections. ​
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For more information about our team and the collection, click on the 'About' section in our menu.
“Radioear Display”. Radioear Corporation Records, 1900-1990, AIS.2023.21, Archives of Industrial Society, Archives & Special Collections, University of Pittsburgh Library System, Box 47, Folder 3.
About the project
Over the course of the semester, we conducted primary research in the archival collection housed at Pitt's University Library System Archives and Special Collections. From this collection, we carefully selected five hearing aids spanning 1924 to 1970, four of which you can explore through interactive 3D scans.
Below, you'll find a timeline tracing technological innovations from the 1200s through the 1900s, alongside the hearing aids developed in response to these breakthroughs. To explore each device in detail, click the "Learn More" buttons or select its name under "Devices" from the menu.
TIMELINE
THE ACOUSTIC ERA
TECHNOLOGY: PRE-ELECTRONICS
1200s-1800s
Acoustic/Non-Electric Methods
Before the invention of electricity, acoustic hearing aids depended on amplifying sound with the material and characteristics of what material was used.
1878
TECHNOLOGY: ELECTRICITY AND THE TELEPHONE
Carbon Microphone Invented
The invention of carbon transmitters and microphones for telephones in the 1870s amplified electrical signals and increased decibel levels by about 15 dB, paving the way to carbon microphones used in carbon hearing aids.
THE VACUUM TUBE ERA
TECHNOLOGY
Vacuum Tube Invented
Vacuum tube hearing aids increased the sound level by as much as 70 dB. These sound levels were achieved because vacuum tubes controlled the flow of electricity better than carbon. Yet, they were still bulky in size until smaller batteries were developed.
1906
THE CARBON ERA
TECHNOLOGY
Transistor Invented
Bell Telephone Laboratories invented the transistor in 1948. Transistors can start and stop the flow of a current and also control the volume of a current, making it possible to have multiple settings in one device. The transistor replaced vacuum-tube technology, which was larger in size and used significantly more power to operate.
1948
THE TRANSISTOR ERA
DNID ENG CAPSTONE (Fall 2025)
By Amy Zhang and Miles Wisner
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Special thanks to Dr. Jason Rampelt, Ben Snyder, Grace Pierce, and the staff at Archives & Special Collections.
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This project was created with the help of Dan Kaple, Digital Creation Specialist with the library's Digital Scholarship and Publishing Team. Scans were created with 3D scanning equipment from the University of Pittsburgh's OpenLab.
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