A body hearing aid is one of the earliest types of hearing aids designed for people with hearing loss. The device is powered by a transistor compartment that's usually no bigger than a deck of cards. A wire runs from this case to a molded piece that's worn in one ear. Early body hearing aids used vacuum tubes that made them two to three times larger than new models. Today, the behind the ear (BTE) hearing aid has largely replaced body hearing aids, except in cases of preference for the larger device or extreme hearing loss.
The history of hearing aids dates back to at least 1588, with the documentation of wooden hearing aids shaped to look like the ears of animals that had acute hearing. By the late 1700s, funnel-shaped devices called trumpets were held to the ear and commonly used by people who had trouble hearing. Trumpets were first commercially produced in 1800. When more complex hearing aids were manufactured in the late 1800s, they were tabletop models that were too large to be easily portable.
The first body hearing aid was created in 1903 and called the "Acousticon." It was bulky, but small enough that the battery compartment could be carried in a handbag. A microphone receiver also had to be worn on the body to pick up sounds that were transmitted to the earpiece. As technology increased and the vacuum tubes that provided the amplification could be made smaller, the size of these devices decreased. After transistors were invented in the United States in 1947, body worn aids became smaller and more convenient to use.
Today, the body hearing aid is only one of the many types of hearing aids available. Some people prefer them, particularly those with profound hearing loss, because the vacuum tubes often amplify sound better than the small BTE devices. BTE aids place a speaker in the opening of the ear and are molded to fit behind the user's ear. In-the-ear devices (ITEs) are also molded to fit, but are better hidden in the outer ear bowl. There are also smaller hearing loss aids that fit in half of the outer ear, and some that are hidden completely in the ear canal.
The body hearing aid is more rarely seen today than any of the other types. Some people prefer them because they're harder to lose and tend to last longer than small BTE aids. Modern designs are shrinking as better technology is available, so many models look almost like a compact MP3 player or other portable electronic device. Instead of being strapped to the body beneath the clothing, modern body hearing aid cases are usually worn in a pocket or attached to the wearer's belt.