A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, 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 or hammer.
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. Historically, many bells were made to commemorate important events or people and have been associated with the concepts of peace and freedom. The study of bells is called campanology.