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Simpson was puzzled why bell-founders quoted a strike note an octave lower than the Nominal. He thought that this was an error by the bell-founders and was not aware of its true significance.
Research this century13 has shown the Strike Note is an apparent frequency heard by the ear shortly after a bell has been struck. The human ear interprets the combination of the short-duration high-intensity Nominal and Upper Quint partials as a note of half the frequency of the Nominal partial. The clarity of the strike note is improved if additional high-order partials are present, e.g. the Double Octave. For a clear strike note the frequency relationship of the Nominal, Upper Quint and Double Octave partials should be 2:3:4. By extending Simpson's proposed Harmonic series from 5 to 8 partials, the Strike Note would be the same frequency as the Prime, making the Strike Note and long-duration note in unison. Unlike Simpson, John William Taylor14 is sure to have been aware of the significance of the Strike Note, and he almost certainly extended Simpson's theories to the high order partials. The figure on the previous page shows that the Nominal, Upper Quint and Upper Third partials for a typical 19th Century bell have a high initial intensity then decay quickly, whereas the Upper Octave is practically non-existent. The bellfounder would need to reduce the intensity of the Upper Third partial, increase the intensity of the Upper Octave and change the frequency ratio of the Nominal, Upper Quint and Upper Octave partials to 2:3:4. The shaded part of the table shows Simpson's theories extended from the first five partials to the eight principal partials.
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