in 1920, the vacuum-tube hearing aid was created by earl hanson who was a naval engineer. similar to the electronic hearing aids, these devices used the transmitter found in telephones to make sounds louder. it would do this by turn sound into electronic current and making it louder and moving it to the ear. vacuum tubes could increase sound by up to 70 decibels, and worked better because they could control electricity better than carbon could. these were first the size of a cabinet, but between the 1920s - 1930s, the hearing aids were made small enough to fit into a small box. the hearing aids were continued to be made even smaller and in the late 1940s, a device that could fit in the pockets was made. this device still connected to the ears through wires so many people still did not think it was appealing.