Ed Nauman had a problem. When he worked in his garage machine shop, the noise levels were often so loud he couldn’t hear the doorbell. He resolved the situation by creating a microcontroller-operated, pneumatically actuated doorbell, or a “Really Loud Doorbell.” He calls it RLD for short. He started with a heavy chunk of steel that would resonate as well as withstand the punishment from a pneumatic ram. It's the beginning of a heavy metal doorbell!