The Sound of Bells

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Epsom, Surrey, St Martin, 10, 16-0-2 cwt in E

Recorded: WAH 27/2/00, 13/3/01
Analysed: WAH 13/4/01

These bells are a complete Mears ten of 1921. Though a pleasure to ring, they are not so tuneful. They have a similar sound to Steyning (Mears 1889). At the time the Epsom bells were cast, Whitechapel were still holding out against true-harmonic tuning. They finally changed their profiles and began to produce true-harmonic bells in 1926 or 1927. The transition to a warmer, less strident tone is exemplified by Bridport (cast at Whitechapel in 1924). Here are the Epsom bells in rounds. Peals such as Leatherhead (tuned Whitechapel 1924) and Whitchurch Canonicorum (tuned Whitechapel 1926) suggest that during the middle '20s Whitechapel could tune successfully but were being held back by their profiles.

Bell Founder Tuning
1 - 10 Whitechapel 1921 -

Tuning of main partials

Tenor nominal: 692 Hz

Bell Hum Prime Tierce Quint Nom'l S'quint O'nom.
1 -2229 -1441 -878 - 1624 661 1176
2 -2212 -1380 -867 -340 1441 665 1189
1191
3 -2158 -1400 -873 -471 1237 673 1206
4 -2152 -1309 -847 -317 1105 666 1198
5 -2159 -1277
-1271
-843 -687 903 664 1201
6 -2152 -1181 -818 -285 711 663 1202
7 -2177 -1201 -825 -360 522 659
661
1191
1194
8 -2177 -1261 -842 -381 411 667 1205
9 -2252 -1170 -852 -437 204 678 1222
10 -2284 -1210 -860 -462 0 678 1220

(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 three of the bells from various points in the peal:

Epsom treble

Epsom sixth

Epsom tenor

Commentary

It is immediately obvious from the table of partials that the tuning of these bells is a little wilful. The nominals show considerable scatter, but appear to be stretched. The sharpness of the third of the scale (i.e. the 8th) together with the stretch gives the peal a bright, albeit a little strident, sound. The average stretch in the octave is 27 cents. Here is a plot of the actual nominals (in cents from equal temperament) and a regression fit:

Epsom nominals

The primes show considerable variation, with the 6th and 9th sharp and the trebles quite flat. Because of the loudness of this partial, especially in the trebles, this does not make the bells too easy on the ear. The hums are quite sharp and loud in all the bells.

The intensity profile of the treble explains a great deal. Bells such as this with loud hum and prime and quiet nominal are deployed to very satisfactory effect both by Taylors and Whitechapel as the trebles on higher numbers. The success of this depends critically on the tuning of hum, prime and nominal being in octaves. In the Epsom trebles the lower partials are not so tuned and their loudness affects the quality of the bells. Here is the sound of the treble. I hear two pitches in this bell, one is the half-nominal heard at the start, and one the prime about a tone below which comes in immediately after. Later, the hum begins to shine through, about a minor sixth below the prime. In changes, the pitch heard I estimate at about 885Hz, i.e. the half nominal predominates in changes due to the shortness of time before the next bell strikes. The plot of partial intensity over time shows the dilemma presented to the ear when the bell is chimed:

Epsom treble partial decays

Clearly, the prime is much louder than the nominal, and after the first 3/4 of a second, all the partials which generate the strike (nominal, superquint, octave nominal etc.) have become very quiet. The hum and the tierce in the chimed bell do not affect the initial sensation of pitch, despite the loudness of these partials. The explanation, as in all bells, is likely that the initial high intensity of the strike-generating partials is not captured well by the analysis.


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Last updated August 14, 2001. Site created by Bill Hibbert, Great Bookham, Surrey