FOR CENTURIES THE HARD OF HEARING RELIED ON DEVICES that looked more like jazz instruments than today’s dime-size hearing aids. The construction of those early devices, such as the ear trumpet, was decidedly low-tech.

More unusual contraptions emerged throughout the nineteenth century, with clever designs to conceal hearing aids in objects such as centerpieces and canes. The acoustic urn channeled sound from all corners of a room while disguising itself as a tabletop decoration. The first electrical hearing aids were developed in the late 1800s using a carbon microphone, but it was not until the 1930s and 1940s that a portable device was developed.

In recent years hearing devices have grown smaller but possess improved sound quality. One lingering problem, however, is the feedback and static that result when a wearer uses a cellular phone. One company has solved the problem by adding Bluetooth to turn the aid itself into a phone.