The History Of the Hearing Aid

Since civilized humans first began creating medical devices a central point of focus has been on enhancing sight and sound, both to make up for inborn deficiencies and to ease the weakening of the senses that can come with age. While advanced technology has only been able to make incremental improvements in aiding eyesight over the last thousand years, with lens technology moving from glass in frames to contact lenses, it's in auditory enhancement devices that modern science has made the greatest strides. In only a hundred years we've moved from ear trumpets to nearly invisible, yet powerful, hearing aids and, increasingly, successors like cochlear implants. The modern era began in the late 1870's with technology pioneered by Alexander Graham Bell's invention of the phonograph. The first devices were literally phones with batteries attached. Then the carbon transmitters were scaled down to use weak electric current for more portable, but still bulky devices which could be carried in bags. A variety of improvements came with amplification technology and vacuum tubes allowing for more power and smaller sizes, but "smaller" in this case still meant "weighing several pounds." In the aftermath of World War II the transistor revolution brought about a sea change in technology, with miniaturization allowing for the creation of the first truly modern hearing aids. Coincidentally these came from Bell Labs, originators of the devices that began it all. Replacing vacuum tubes with transistors not only meant smaller, lighter devices, but also less heat, longer battery life, and greatly reduced distortion. Unfortunately they only lasted a few weeks, so the transistor based models continued to be sold. Continuing research showed that the issue was peoples' body heat and perspiration causing the units to burn out, which led to all-transistor models with coated components and the eventual addition of silicone transmitters. Improvements continued until the late 50's when the IC, or integrated circuit, began to replace transistors, allowing for even greater miniaturization and battery life. While these offered many advantages they were still only effective for certain types of auditory loss and usually still required a multi-part unit, albeit small enough for the components to be mounted on eyeglasses or similar personal items. Meanwhile, back at Bell Labs, mainframe computers were being used to synthesize and encode human speech in to computer code based waves. This research dovetailed with the IC's replacement, microprocessors, in the mid-70's to allow the creation of small digital devices capable of mutli-channel audio signals. Consequently, ear-mounted devices using a compact transmitters were created, continuing the trend of miniaturization culminating with modern digital-analog compact single unit devices in the late 1980's. After their successful launch, AT&T, Bell's descendant, finally left the market it had begun almost 100 years before. Since the advent of those hybrids, digital technology has improved dramatically, leading to the development of "smart" all digital devices that don't need volume controls or require adjustment for different environments, but instead use software to sense ambient noise levels and self-adjust. Researchers continue to improve the technology with better chips and smarter devices that can better "understand" speech, with the final frontier being implantation of chips directly in to the ear, replacing the worn out or damaged parts left by nature. Aids may be replaced with true bionic ears. Given the exponential speed of advancements in this field, who knows what tomorrow will bring. Just as Alexander Graham Bell certainly didn't guess when he spoke in to his first telephone that his "hello" would reverberate in to a century of solutions to hearing loss, so today's researchers can only guess how far we'll go in the next 100 years.