Bells are percussion instruments from the idiophones family, being devices to produce sound which are simple only in appearance. The bells bodies are made of an alloy called bronze, which is a combination of copper and tin in a variable ratio. Inside the bell there is the clapper, a pendulum that hits the bell from inside in order to start the sound. Bell foundry is quite complex and involves a large number of procedures which range from the construction of the molds until the metallurgy and its tuning. The modern bell suffered only minor changes in its shape when compared to the first casted bells from the 9th century. Complex mathematical methods are needed to create acoustical models for vibrating bells and, due to their exaggerated size, it is difficult to transport them to a laboratory in order to perform experimental analysis. This article presents a brief discussion on the origin, history and uses of the bell, as well as the main steps in the casting process and the physical description of the vibrating bell.
bell; campanology; acoustics; natural frequencies of vibration; physics and music
