One truly unique element of hearing aids often seen most prominently in the advanced bespoke private hearing aids found by a dedicated audiologist is that hearing aids are a very advanced evolution of a centuries-old concept.
Hearing aids have existed in at least a very primitive form since the 17th century as described by mathematician Jean Leurechon and as an electronic amplifier since 1895. However, the biggest evolution in hearing aid technology took decades to truly come to fruition.
Digital Hearing Processors
One of the first major points of interest when computers started to become increasingly sophisticated and practical in the 1960s was audio processing.
Part of this was for telecommunications, and indeed the first online call would happen in the mid-1970s, but another critical research path was the study of speech processing and how this could be used to make better, more tailored hearing aids.
This was an exceptionally long process, in no small part because computers took a very long time to become small enough and powerful enough to process audio in real-time.
Whilst Moore’s Law was in effect and computers were getting more powerful, smaller and cheaper at a phenomenal rate, computers available in the 1960s were room-sized and not fast enough to take real speech, process it into data and return the result to an earpiece without considerable delays.
What it could do initially, however, was allow for some of the foundational studies into speech analysis that would allow this work to be undertaken in the future.
The first major result of this was the Block of Compiled Diagrams (BLODI), which allowed for any speech that could be registered as a block diagram to be synthesised.
At the time, computers were only able to process or playback the digital signals, meaning that it was impractical as an actual hearing aid given that the process of digitising speech could take days, but it showed that it could be done.
The breakthrough moment was in 1967 when a hearing aid was simulated entirely using BLODI by Henry Levitt, which was the first step towards more practical hearing aids.
This came to fruition in the 1970s through the development of “hybrid hearing aids”, which used the conventional amplification and filtering of typical analogue aids but also had the capacity for digital programming and tuning via a computer.
This allowed for hearing aids that were easier to develop and fine-tune for the needs of different people and allowed for adaptive noise filters, reducing some of the early audio ephemera that was a problem with very early analogue hearing aids.
The final step of this process came in the 1980s, when a team at Washington University, including Mr Engebretson, Mr Morely and Mr Popelka developed the first truly digital hearing aid, having managed to develop a battery-powered, tiny computer system that was powerful enough to process digital audio signals in real-time.
This allowed for hearing aids to not require a separate box but could have all of the components supplied behind the ear, and later in the ear itself, whilst also featuring the ability to program the hearing aid digitally, self-calibration and self-adjustment.
