This is from http://www.acoustics.org/press/133rd/2pmu1.html
Thomas D. Rossing
Acoustics of Eastern and Western Bells, Old and New
Acoustical Society of America
After the 3rd century A.D., round temple bells gradually replaced two-tone bells. Many cities placed large bells in towers to announce the time of day. The most famous temple bell in Korea is the magnificent King Songdok bell, cast in 771 A.D. during the Silla dynasty. Standing 3.66 m high, it has a mass of nearly 20,000 kg. The largest known Chinese bell, standing over 4.5 m high, was cast in the 15th century during the reign of the Ming emperor Yongle.
Bells developed as Western musical instruments around the 17th century when bell founders learned how to tune their partials harmonically. The founders in the Low Countries, especially the Hemony brothers (Francois and Pieter) and Jacob van Eyck, took the lead in tuning bells, and many of their fine bells are found in carillons today.
Bell tuning standards and practices changed very little from the time of the Hemony's until just a few years ago, when a team of scientists and bell founders in The Netherlands developed a new type of carillon bell in which the dominating minor third partial of the traditional bell is replaced by a major third partial. Now it is possible to build carillons of either minor-third or major-third bells (or even both together).
Handbells date back at least several centuries B.C., although tuned handbells of the present-day type were developed in England in the 19th century. In recent years, handbell choirs have become popular in schools and churches, some 40,000 handbells choirs have been reported in the United States alone. Tuned handbells are generally made of cast bronze, which has been the traditional bell material for many centuries.
Demand for handbells of lower and lower pitches has led to the development of bass bells as low as G0 (fundamental frequency of 24.5 Hz). Bronze handbells tuned to this pitch radiate inefficiently, however, since the vibrational waves travel considerably slower in the bells than they do in the air nearby, thus creating a sort of acoustical "short circuit." In order to obtain a higher radiation efficiency and thereby enhance the sound of bass bells, the Malmark Company has created a new bell design using aluminum rather than bronze. These new bells are larger in diameter and radiate much more efficiently than bronze bells, yet they are lighter in weight. In our laboratory at Northern Illinois University, we have studied the modes of vibration of these bells (using holographic interferometry) and also the sound radiation.
These are but a few examples of how scientists and bell designers have teamed together to further improve one of mankind's oldest musical instruments.