Approximately six million Americans use a hearing aid, not all of whom are elderly. Though just about everyone knows someone or has seen someone wearing a hearing aid, most people do not understand how they work.
Modern hearing aids are a far cry from the huge ones that many of our grandparents used to use (though some of this type are still available). They are tiny digital electronic devices that can sit either in the ear or on top of it to selectively amplify and process sounds so they can be sent into the inner ear of the wearer. In the same way that a performer speaks into a microphone, which then projects the sound of his voice to loudspeakers, a hearing aid is basically a tiny version of that technology.
All hearing aids used to be analog, and the less expensive ones still are. An analog hearing aid merely amplifies the sound as is and sends it to the speaker. The advantage of digital technology is that it allows for a more complex processing of sound that was not available before. For example, speech can be separated from general ambient noise, which is one of the main problems many hearing-impaired people have when trying to have a conversation in a crowded restaurant.
A digital hearing aid can separate the parts of sound into different ranges of frequency so that the device can be programmed to suit the needs of the wearer. For instance, if you are a symphony conductor, the range of frequency you need will differ from someone who drives a bus. A digital hearing aid can also be adjusted as time goes on, in case there is a change in hearing ability or there is a need to adjust the frequency to hear different types of things.
Digital processing in hearing aids also allows for the amplification of different levels of sound. So if you suddenly go from a library out onto a noisy street you will not experience painfully loud traffic noise blasting in your ears. In addition, by processing the sound signal digitally it ensures that there is the least amount of sound distortion, providing clear sound with better quality than was possible in the past.