Hearing Aids

It's hard to notice today's tiny hearing aids. Most consist of a fingernail-sized case of electronics and batteries that hides behind the ear and a thin translucent wire with a tiny speaker that fits inside. Most come with an app that lets users adjust their multiple microphones to focus on someone’s speech or suppress background noise in crowds.

They are a far cry from the animal horns and metal cones that were a source of humor in early black-and-white movies. They are also a lot more useful. 

Biomedical engineers have been improving hearing aids since the first transistors reached the market in the 1960s. They were quickly followed by chips whose integrated circuits contained all the electronics needed to process sound. Once they digitized sound, audiologists could boost or suppress different frequencies to make sounds clearer to the listener. Users could control volume and switch settings for indoor or outdoor sounds.

The big breakthrough came in the late 1980s, when engineers introduced digital signal processors (DSPs) for hearing aids. Until then, conventional integrated circuits struggled to translate the analog sound created by compressed air into a rich pallete of digitized data. This limited how they could process the incoming signal.

DSPs were designed to breeze through this task. Suddenly, it became possible for hearing aids to reduce background noise, amplify soft sounds without distorting loud ones, cancel feedback, and use multiple microphones to better isolate sounds coming from in front of the user. 

Modern hearing aids continue to build new functionality into their circuits as they grow ever smaller. Today's devices link directly to smartphones, TVs, and even sound systems in theaters. They replaced disposable batteries with USB-rechargeable power. Artificial intelligence enables them to better adapt as the sonic environment changes while providing even greater app control.