Why does the Beetham Tower hum?

With storms predicted over much of England tonight, I wonder if the Beetham Tower in Manchester will put on another howling performance? This is my recording of the last time the Hilton hummed in 2012:

Simon Jackson (@stjackson), of the acoustic-consulting firm Arup, tweeted, โ€œQuick sound level measurement at Beetham Tower – 78dBLaeq,1s main freq in 250Hz 3rd/oct bandโ€. Simon later told me this was from about 100 metres away. No wonder people complain, that is similar volume to hearing a performance from a nearby tenor saxophone. Although given the way the hum starts and stops as the wind picks up and slows down, producing a single note which varies slowly in loudness, people more often liken the sound to an alien space ship coming into land.

The glass blade that causes the hum
The glass blades at the top cause the hum [1]

The problem is caused by the glass and metal sculpture at the top of the building. When the wind rushes past the edge of the glass panes turbulence is created. On its own, the turbulence from an edge doesn’t create very much noise, but it then gets amplifyied via resonance. For the Beetham Tower, I suspect it is the resonance of the air between the deep glass panes which allows the hum to achieve such loud decibel values.

How to solve the hum?

You either need to stop the turbulence being generated, or reduce the resonant amplification. This sounds simple, but this sort of noise problem is notoriously difficult to solve. [3] Work has already been done to reduce turbulence, most recently by connecting 1800 aluminum profiles to the glass panes. These reduced the turbulence but the building still hums at very high wind speeds. To stop that humming, maybe the next thing to tackle is the resonance. This could be reduced by altering or removing some ofย  the glass panes, as was done in for other whistling towers. [2]

Notes

[1] http://www.ropetask.com/index.php/case-studies/beetham-tower/

[2] “Buildings that whistle in the wind”. New Scientist Tech. 4 August 2006.

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0 comments

  1. Hello again Trevor, thanks for posting this, first time I’ve seen it set out in plain English.
    I live nearer @AngryBeetham now and on Wednesday night it was quite insane, I thought it was howling through my roof. Hard to explain that even inside my flat it was less of a “hum” and more of a “Martian-death-machine-from-Geoff-Wayne’s-War-of-the-Worlds”.
    Very glad the wind just dropped at half-7…

  2. Thank you for the interesting article Trevor. I wonder could the humming have been predicted before the building was completed?
    The humming on Wednesday was the loudest I’ve heard, particularly in Piccadilly Gardens. Would the sound be loudest in the flat at the top of the tower or would it be louder downwind?

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