Big Ben’s bongs could soon strike an unfamiliar note

By THE distinctive bongs of Big Ben could have a different sound after refurbishment, experts have said.

Britain’s best-known bell will soon fall silent for several months as part of a three-year, £29 million revamp to repair the Elizabeth Tower and clock.

Officials have said that the clock is in such a “chronic state” that it may fail if work is not carried out urgently.

But experts at the University of Leicester, who have recently carried out laser vibration mapping to find out how the 13.5-ton bell produces its characteristic sound, say that renovation work could alter the frequency of sound waves and length of the bong.

Removing accumulated soot or making repairs to the crack in the bell may change its tone, while plans to renovate the tower’s structure, including refitting the frame around the bell, could impact how long the bong resonates.

Big Ben has never been tuned, so restorers may take the opportunity to make the bell sound closer to what was originally intended. When first fitted by the Whitechapel Bell Foundry, the clapper was too large, causing a crack to appear and leading to its peculiar dissonant sound. Consequently, not rung true since 1859.

Amy Stubbs, of the advanced structural dynamics evaluation centre (ASDEC) at Leicester University said: “The sound of Big Ben is entirely unique and made up of a number of different frequencies, all of which make it quite easy to identify when you hear it on the news or the radio. We all know the sound intimately.

“If you make any changes to a bell then that will alter its sound, for example the crack is having an effect on the way it vibrates, which is why it has a dissonant sound, unlike say that of St Paul’s Cathedral. It wasn’t tuned, even when it was new, so if they do any tuning or take any metal off then the sound could change. If it’s very dirty they may remove the soot.”

However, she added: “It’s likely to be a very small difference in frequencies, maybe just a fraction of a hertz, which could be imperceptible to the human ear.” The bell already has an unexpectedly high sound for such a large cast- ing, which experts believe was the result of an amateur designing its shape. It will be the third time that the chime has not rung out in 150 years, having previously stopped for nine months of repairs in 1976 and six weeks in 2007. During the new refit, the clock faces could be returned to their Victorian green and gold paint. To determine the frequencies which produce Big Ben’s sound, the Leicester team created a 3D computer model of the bell and mapped the sound vibrations in the metal as it chimed. Martin Cockrill, who leads ASDEC’s measurement team, said: “You cannot just glue sensors to a national treasure such as Big Ben. “Aside from the technical aspects, one of the most challenging parts of the job was carrying all of our equipment up the 334 steps of the spiral staircase to the belfry. Then to get everything set up before the first chime, we were literally working against the clock.”