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By Doug Millard on

Sound Advice

I set out to the National Physical Laboratory the other day and on my way down Exhibition Road passed an elephant.

Some 250 of these colourful models are being positioned across London to raise awareness and funds for the plight of their living cousins. A little later something niggled at the back of my mind – as though that elephant was trying to tell me something – but I thought no more of it and caught a train for Teddington and the NPL.

This, I’m ashamed to say, was my first visit to the Laboratory, also known as the National Measurement Institute, where, for over a century, physical standards have been measured, studied, applied or all three.

Scientists at the NPL, 1932
Scientists at the NPL, 1932 (Science Museum/Science & Society)

It was International Metrology Day, May 20th – exactly 135 years since seventeen nations agreed to the metre as the fundamental unit of length. The original Metre, made from platinum and iridium, is housed in Paris but the NPL has one of the carefully guarded official copies. These days a Metre is defined by the distance light travels in a vacuum during 1/299 792 458 of a second.

NPL also does a lot on sound – acoustics – and I was particularly impressed by the Laboratory’s anechoic chambers.

Science of Acoustics, 1850
Science of Acoustics, 1850 (Science Museum/Science & Society)

Now, while the Science Museum has all sorts of acoustics objects and pictures in its collections it has nothing like the NPL’s rather fearsome looking chambers where sounds produce no echo; here’s a link to one of the NPL’s anechoic chambers in action.

The NPL studies all manner of sounds, those the human ear can readily detect but also those at too high a frequency for us to hear – ultrasonic – or too low – infrasonic. Other animals are different, though: elephants, for example, have been shown to communicate using really low frequencies. Scientists suggest that this allows them to coordinate their own movements over distances of many kilometres. Maybe the Exhibition Road elephant was trying to tell me something earlier that day.