How does the shape of a bell affect the sound (tone)

For the Sound Elective group work presentation, my current interest relates to the the shape and thickness of bells. Bells are known throughout the world as a spiritual instrument and interestingly has no accruate origin or date it was invented with examples around the world from the Chinese dynasty to Western Europe. Despite this distance, the function of a bell within particular cultures was used as a religous/spiritual and even superstitius symbol.

Interesting article here regarding the history: http://www.handbells.org.au/history/genhist.htm

'In medieval times bells were steeped in superstition. This was probably because of their long association with religion. They were baptised, and once baptised had the power to ward off evil spells and spirits. Bells were hung in doorways to protect visitors and the visited from the evil spirits which always wait around the door awaiting the chance to slip inside. A visitor would ring the bell to drive the spirits away then pass inside - which is the likely origin of the present day doorbell!'

How bells make their sound is a complex but interesting subject. The discussion here is restricted to bells of typical 'western' profile, rather than those of the east which have a very different shape. Western bells are usually hit by an iron clapper at a point on the inside, near the bottom, or by an iron clock hammer at an equivalent point on the outside. This impact causes the bell to vibrate in a number of different ways or modes. Each mode can have a different frequency, intensity, attack and decay time, and can be characterised by 'stationary' points or nodes, both around the rim, and vertically up the bell.

Taylor 1980s (Using a Seiko Chromatic Tuner ST-747) Chromatic scale note is D


Gillett and Johnston 1920s (Using a Seiko Chromatic Tuner ST-747) Note is A


Mears 1850s (Using a Seiko Chromatic Tuner ST-747 at 440Hz) Chromatic scale note is F


Rudhall 1730s (Using a Seiko Chromatic Tuner ST-747 at 440Hz) Chromatic scale note is A


Eldridge 1670s (Using a Seiko Chromatic Tuner ST-747 at 440Hz) Chromatic scale note is D#


York Foundry 1500s (Using a Seiko Chromatic Tuner ST-747 at 440Hz) Chromatic scale note is A


London 1400s (Using a Seiko Chromatic Tuner ST-747 at 440Hz) Chromatic scale note is C#



I found this image on a blog and thought it was very interesting on:
how the shape of a guitar would affect the sound

Another great link: http://entertainment.howstuffworks.com/guitar2.htm