1997: Prisma. A Computer for the Ear

A new era in hearing aid technology began in 1997: Prisma was launched, the world’s first completely digital hearing aid with two microphones, which automatically adjusted to the current hearing situation.

Following three decades of gradual improvements, a new era in hearing instrument technology began in 1997: Siemens launched its Prisma hearing aid, the world’s first completely digital hearing instrument with two microphones, which automatically adjusted to the current hearing situation. From a soccer stadium to inside a car or at a conference, processors eliminated disruptive noise and adjusted the volume in milliseconds. The benefits of digital technology were already apparent during the fitting stage, when the acoustics technician used software to amplify insufficient signals in the damaged frequency ranges.


A part of the product range, 1997

At 18,000,000,000,000,000,000 – or, to put it differently, 18 quintillion – there was almost no limit to the different settings possible with Prisma hearing aids. But there was good reason for this great variety, since a person’s individual sense of hearing is practically unique. The likelihood that two people will have an identical sense of hearing is about the same as the chance of finding someone with identical fingerprints. Naturally, it was not necessary to try out all 18 quintillion settings individually. The acoustics specialist measured the patient’s individual characteristics and used the software designed for use with the instrument to adjust the digital hearing aid to the wearer’s hearing ability.

A digital hearing aid does not simply make ambient noise louder. Instead, it detects the situation, filters out disturbing noise, and specifically amplifies speech. Siemens calls this technology “speech-sensitive processing.” Prisma hearing aids supported this system with a new technical feature, the TwinMic System. It had one directional microphone for focused listening and an omnidirectional one to pick up the full spectrum of sounds; the wearer was able to switch easily between the two microphones. Other devices, such as a CD player or cassette recorder, could also be plugged into the audio input jack.

With all these benefits, the Prisma was still easy to use, comfortable to wear, and discreet. Patients with hearing loss were able to choose from various configurations depending on their preferences and needs: The Prisma CIC (Completely in the Canal) was tiny, fit deep inside the ear canal, and was barely visible to others. Other in-ear versions varied in size and in terms of the range of available features. A color chart was available for the Prisma BTE hearing aid to match it to the wearer’s skin tone.