Bell

A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually an open-ended hollow drum which resonates upon being struck. The striking implement can be a tongue suspended within the bell, known as a clapper, a small, free sphere enclosed within the body of the bell or a separate mallet. Bells are usually made of cast metal, but small bells can also be made from ceramic or glass. Bells can be of all sizes: from tiny dress accessories to church bells weighing many tons.

n the Roman Catholic Church and among some High Lutherans and Anglicans, small hand-held bells, called Sanctus or sacring bells, are often rung by a server at Mass when the priest holds high up first the host, and then the chalice immediately after he has said the words of consecration over them (the moment known as the Elevation). This serves to indicate to the congregation that the bread and wine have just been transformed into the body and blood of Christ (see transubstantiation), or, in the alternative Reformation teaching, that Christ is now bodily present in the elements, and that what the priest is holding up for them to look at is Christ himself.

The process of casting bells is called bellmaking or bellfounding, and in Europe dates to the 4th or 5th century. The traditional metal for these bells is a bronze of about 23% tin. Known as bell metal, this alloy is also the traditional alloy for the finest Turkish and Chinese cymbals. Other materials sometimes used for large bells include brass and iron. Bells are always cast mouth down.

Bells are made to exact formulas, so that given the diameter it is possible to calculate every dimension, and its musical note, or tone. The frequency of a bell's note in Hz varies with the square of its thickness, and inversely with its diameter. Much experimentation has been devoted to determining the exact shape that will give the best tone. The thickness of a church bell at its thickest part, called the 'sound bow' is usually one thirteenth its diameter. If the bell is mounted as cast, it is called a "maiden bell" while "tuned bells" are worked after casting to produce a precise note.