The science behind considered one of UK’s most iconic sounds
A signature sound for Great Britain is the bongs of Big Ben, the large bell housed inside the clock tower of the Houses of Parliament. And tonight it can welcome within the New Year. There is one thing particular in regards to the sound. Listen to a bell chime and what at first appears a easy ring is definitely a really advanced sound. Why does it begin with a clang? Why do the bongs have a dissonant warble?
At the beginning of the primary strike there’s a clank of steel on steel because the hammer hits the bell, which regularly fades right into a sonorous ringing. While the preliminary hammer blow creates numerous excessive frequencies, these quickly die away, leaving a gentler low frequency ring, which slowly warbles. The begin of the be aware, the assault, is a fleeting second, however it’s extremely necessary to figuring out what’s making the sound.
You can see all these options within the spectrogram beneath, which reveals how the frequency content material of the bell sound varies over time. The darkish horizontal traces present the frequency parts that make up the bongs. At the start to the left there are many darkish traces throughout all frequencies from prime to backside – that’s created by the clank of steel on steel. But the excessive frequencies have disappeared later as proven to the precise. The warble present up as a dashed horizontal line, as a result of that frequency part of the sound retains fluctuating between quiet and loud.
The warble is created as a result of Big Ben isn’t completely circularly symmetric. A big crack opened up on one aspect shortly after it was first put in as a result of they used a hammer that was too heavy. This asymmetry modifications how the bell flexes.
If you have a look at the video above and also you’ll see a bell (not Big Ben) vibrating. These are the vibration patterns on the varied frequencies that make up the bell sound. If a bell is just not fairly circularly symmetric, you truly get two notes being created which might be very shut in frequency. These then create beats the place you hear a sound that’s at a mean of the 2 frequencies, which retains slowly modifications in amplitude from between quiet to loud. The video beneath has a pleasant demo about 1:20 into it. Beats is what creates the Big Ben Warble.
You can’t at present go to Big Ben as a result of it’s being renovated. But that is what it’s like:
“A big 200 kg hammer drew again slowly earlier than crashing ahead and hanging the surface of the bell. Even with ear plugs in, the sense of energy was visceral. The sound resonated the air in my chest like a pumping bass line in a nightclub. “
Sonic Wonderland / The Sound Book.
Big Ben is the long-lasting sound of New Year for the UK however what’s the equal in different international locations? Please let me know by commenting beneath.
Ben Ben modes: Advanced Structural Dynamics Centre on the University of Leicester