Harvey Fletcher's Hearing Aid

Harvey Fletcher is credited with the invention of the hearing aid. He kept secret that he was part of the famed oil drop experiment with Robert Millikan until his death. Later in his life, he helped understand the natures of speech and hearing. When put in the ear, the hearing aid allows the user to focus in on specific sounds, down to beating heart of a hummingbird. Unfortunately, this causes the person to be more vulnerable to loud noises or sounds with high or low frequencies.