From Acoustic Cones to the Bionic Ear

The more than 300 yearlong technological journey that was, eventually, to culminate in the bionic ear would appear to have begun in the 17th century. At that time, many of those who had been battling to understand the words of others must have been grateful for the shell-like metal structures that, when placed over their aural appendages, served simply to direct sounds more precisely into the auditory canal.

There seems to have been little genuine progress for some time following this early development and, at the beginning of the 19th century, the available devices were not only so large and heavy that they needed to be supported on a table but were not particularly effective either. Among the more practical, if rather amusing, solutions of the period was the speaking tube. This allowed a speaker to talk at one end in order to communicate with a listener at the other.

The discovery that the conical shape could actually serve to amplify sounds led to the so-called acoustic cone; a sort of dunce-cap arrangement held against the aural orifice. Attempts to reduce the size resulted in the introduction of curved and folded conical structures similar to those used, for the same reason, in the design of certain musical instruments. Thus, at the end of the 19th century, the pinnacle of hearing aid technology was the ear trumpet.

Unfortunately, although these devices were much smaller than their precursors, their size continued to remain a problem. In use, they drew attention to an impairment that most would rather have concealed. This embarrassment was to remain problematical until the dreamed-of minute digital devices and bionic ears of today became a practical reality.

The advent of electricity and the telephone brought with it the first genuine revolution in hearing aid technology. It began with the first commercially produced units from Siemens in 1913. Still large and not very portable, they were hampered by the size of the components of the time. However, by the 1930’s they had become small enough to be wearable and the public began to accept them.

Digital electronics and RF technology have led to devices that are small enough to be worn inside the ear and that operate wirelessly. The greatest breakthrough, though, has been for those who are profoundly deaf. Today they may have amplification devices surgically implanted, making them completely undetectable.

Known as cochlear implants, these devices do not operate in the same manner as conventional hearing aids but rather create the perception of sound through electrical stimulation. The development of these devices began in the 1950s and mostly involved experiments to better understand the physiology of hearing. In 1978, an Australian – Professor Graeme Clark led the team that performed the first successful implantation. Today, it is estimated that over a quarter of a million patients have been helped in this fashion.

These devices have both external and internal components. The former consists of microphones, speech processor and transmitter and are all easily concealed. Internally, the receiver and stimulator is embed in the bone behind the ear converting incoming signals to electrical impulses that are passed by a cable to an array of electrodes wound into the cochlea. Though the resulting sounds differ from normal speech, the bionic ear is improving lives daily. 

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