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Throwback Thursday to the 1946 Oticon Model TA

Scientific achievements in hearing aids
Eriksholm Research Centre houses on of the world’s most complete collections of hearing aids and related items. A stroll through this treasury inspired yours truly to share some of the scientific achievements, which have impacted where audiological research is today.


It is hard to imagine, but the 1946 Oticon TA hearing aid was once state-of-the-art. It is oversized, it is clumsy, the battery pack looks larger than the device itself, and there are enough tangled wires going in and out to make anyone, who has ever owned a pair of headphones, lose their mind. Nevertheless, it marked an important milestone in the Danish hearing aid industry, and set a precedent for every technological innovation that followed.

Over the next few installments of our “Throwback Thursday” series, we look at seven decades of scientific innovations, and dig up interesting stories, that serve as milestones on our continuous research path. We start our journey in 1946 in Copenhagen, Denmark, with the release of William Demant’s first hearing aid, the Oticon TA. He built the first prototype at the Oticon plant at Amager, Copenhagen, just a few miles from the headquarters at Gammel Torv Several times a week, William would take the tram, to go down to the plant and meet with the people manning the production lines.

Because of the international turmoil going on in the world during the 40s, William found it difficult to import the numerous supplies he needed to manufacture hearing aids under license. There were a number of trade embargos on European countries, and Denmark’s biggest trade-partner, Germany, had great difficulty keeping up trade relations with the rest of the world, following the Second World War. This forced William Demant to set up a shell company in Sweden, and source all his supplies through that. Every now and then, William would travel to Sweden, pack a suitcase full of materials, and bring them back to his plant in Copenhagen, to continue building his device. For a long time after the device was mass-produced and marketed, materials were still imported via the Swedish border.

The model TA was the first heavy-duty hearing aid produced by a Danish company. The aid used a crystal microphone to pick up sound. As the first hearing aid ever, it also utilized vacuum tube technology, installing tiny, wired tubes to amplify sound, and play it back to the user. Inspiration for this technology came from the American military, in which they used this same principle to power long-range communication devices such as portable radios.

If you think your smartphone runs out of power too fast, you may be happy to know things used to be a lot worse. When the Oticon model TA hit the market, it boasted a battery life of up to 8 hours of use. The large batteries, developed by the Danish company Hellesens, cost up to $3 ($62 in present value) per battery. At a rate of $3 per battery and 8 hours of lifetime, a hearing aid – even if used scarcely – could easily cost up to $100 ($2,000 in present value) per year, in battery expenses alone.

To combat this drainage – not only of power, but also of wallets – development began on a voltmeter that could measure the remaining power on the batteries. The idea was to switch your batteries before they ran out of power, and let them recharge a little; similar to the way some of us might remember leaving our phone off for a while, to crank those extra two or three percentage points of battery out of it. The voltmeter became the standard practice for saving power in the model TA hearing aid, all the way up until transistor-based hearing aids became the new standard, and battery usage dropped by around 90%.

When released, the Model TA was a wildly popular hearing aid despite the high price tag on both the hearing aid, and subsequently the batteries. It continued to sell for almost a decade, and truly made its mark on the hearing aid industry, not only of the day, but every iteration that followed as well.

You can learn much more about the rich history of audiology and hearing aids in The Eriksholm Collection, where we catalogue more than two centuries of hearing aid history, and interesting pieces of mechanical devices.