The Sound of Bells

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Chalford, Gloucestershire, Christ Church, 6, 10 cwt in G - Steel Bells

Recorded: WAH 23/2/01
Analysed: WAH 2/3/01

These bells are a Naylor Vickers steel six of the late 1850s. The inscriptions describe them as being E. Riepe's patent cast steel. They have a typical steel-bell sound, somewhat improved (I was told by the tower captain) by having rubber clapper lifters. They were originally fitted with clapper-lifting springs which, having fallen into disrepair, were replaced by lifters which had been fitted as an experiment to a peal of bells in Bristol. Having rung on a couple of peals of steel bells, I was delighted to be given permission to record and analyse these, to see how their partial frequencies and intensities would compare with bronze bells. All is revealed below. Here are the bells being rung in rounds.

Bell Founder Tuning
1 Naylor Vickers 1858 -
2 Naylor Vickers 1857 -
3 - 6 Naylor Vickers 1859 -

Tuning of main partials

Tenor nominal: 736 Hz

Bell Hum Prime Tierce Quint Nom'l S'quint O'nom.
1 -2171 -1171
-1163
-872
-865
-272 928 698 1271
2 -2361 -971 -875 -396 778 728 1300
3 -2110
-2124
-1155 -891
-883
-249 533
538
711
717
1291
4 -2104 -1139
-1125
-887 -237 399 724 1305
5 -2129 -1080
-1067
-876 -269 249 735 1321
6 -2075
-2059
-1120
-1111
-873 -208 0 728 1303

(The figures in this table are all given in cents. For all partials except the nominal, the partials are given from the nominals of the bell. Cents of the nominals are relative to the tenor. Pairs of values indicate a doublet. Frequencies for the quint are often not given, especially if inaudible.)

Intensity plots

Here are the spectra of all six shown together:

Chalford 1 to 6

Commentary

One should start with the nominals of these bells. My estimates of the pitches of the bells suggest that they pitch roughly at the half-nominal as do bronze bells of ordinary profile. However, to check the bells were not intended to be pitched by hum or prime, the table below shows the frequencies of all these partials related in cents to the frequencies of the tenor, compared with the equal tempered intervals:

Bell Hums Primes Nominals Equal temp.
1 832 876 928 900
2 492 927 778 700
3 504 503 533 500
4 371 380 399 400
5 195 302 249 200
6 0 0 0 0

Due in the main to the rather wild tuning of the second's prime and hum, only the nominals give a pitch sequence which is even in the right order. Clearly the manufacturer of these bells was pitching by the nominals, but they are not particularly well tuned. All bells except the fourth are sharp of the tenor, the second being over 3/4 of a semitone sharp.

Turning now to the other lower partials, there is no consistency in their tuning from bell to bell. All hums apart from the second are sharp, the tenor sharpest of all at two whole tones above the double octave. Primes are a little sharp, which can spoil tone in a bronze bell. In the second, the prime is so remarkably sharp that only by plotting its intensity profile over time was I able to be certain that this frequency was not a very wide doublet on the tierce. Prime and tierce in this bell are only 38 Hz apart, a recipe for poor tone. On the other hand, the hum in this bell is an almost perfect double octave - it stands quite clearly apart from the others in the intensity plot above.

The tierces in these bells are actually very well controlled compared with the other partials. The quints tend to be sharp - which is said to give a shriller tone - and the superquints and octave nominals are all well sharp of their position in bells of normal profile. The intensity plot confirms the unusual positioning of the partials, and shows a number of elements - loud sharp hums, and energy in the higher partials - which together would lower the quality of bronze bells. These bells actually share a lot of characteristics with poorer 19th century bronze bells.

It's not apparent from the information presented here, but despite the clapper lifters the various partials in the bells die away quite quickly, which in bronze bells gives a dry, breathless tone. This one supposes is a characteristic of their metallurgy, though the decay times of these bells with lifters are no worse than for bronze bells without. (I recorded the bells rung up to the balance.)

So, what to conclude? The first and most interesting point is that the partial disposition and intensity profiles of these bells can be interpreted as for bronze bells - the material does not make a fundamental difference to the partial structure. Second, it is clear that the detailed tuning of the partials departs sufficiently from accepted practice to make certain that the sound of the bells will be unusual whatever their material. Could these bells be tuned along conventional lines? The wide deviation from standard of the partials suggests a physical profile which might make this difficult - there may not be enough metal in the right places to make conventional tuning possible. I do not know if these bells were tuned when first cast - perhaps Riepe's patent would shed some light. The accuracy of the tierces compared with the rest of the partials suggests some tuning was done. However, one should probably regard these bells as a maiden peal from a founder who did not have the knowledge to control sound quality and timbre through profile. That, rather than the metal of their construction, determines the sound we hear.


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Last updated March 2, 2001. Site created by Bill Hibbert, Great Bookham, Surrey