This article was taken from the August issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content bysubscribing online
How do we know how long a second lasts? Who decides that? It turns out the answer to this -- and pretty much every measurement-related question ever asked at a pub quiz -- can be found in Teddington, Middlesex, the home of the National Physical Laboratory.
It’s here that you’ll encounter the tools for measuring anything and everything the UK government and industry needs tested to standards. Last year 6,988 calibrations were performed for the lab’s clients. Here’s just a small sample of the tools it uses.
1. NanoSurf IV (above)
The NanoSurf (short for nano-surface) was designed to measure standards -- blocks with given shapes and dimensions -- that are then used to calibrate other measuring instruments. The tool is housed in an acoustic and thermal insulating box and is made of a translucent glass-ceramic.
The NanoSurf IV uses a diamond-tipped stylus to trace the surface of nano-scale materials and can measure surface textures with a precision of 1.3 nanometres.
<img src="http://cdni.wired.co.uk/309x428/g_j/Hemi-anechoic-chamber.jpg" alt="Hemi-anechoic chamber"/>
2. Hemi-anechoic chamber
In here you can literally hear a pin drop. Anechoic means “no echoes”. This space, covered in soft fibreglass wedges that absorb sound waves, is purpose built to test acoustic equipment for industries as varied as medical ultrasound and oceanographic research. The 8 x 8 x 5m space’s exceptionally low levels of background noise have led food manufacturers to use the lab to study the “crunch” properties of crisps and biscuits.
<img src="http://cdni.wired.co.uk/309x428/a_c/Acoustic-Ear-Simulator.jpg" alt="Acoustic Ear Simulator"/>
3. Acoustic ear simulator
You can record sound with a microphone, but to understand how humans really hear you’ll need one of these. This acoustic human-ear simulator records airborne sounds using ultra-sensitive microphones in the simulated-ear canal to convert sound waves into electrical signals. Recently, NPL measured the sound-pressure levels produced by in-ear headphones to ensure they did not exceed legal limits.
<img src="http://cdni.wired.co.uk/309x428/o_r/Reverberation-Room.jpg" alt="Reverberation Room"/>
4. Reverberation room
Almost the exact opposite of the hemianechoic chamber, this is where noise goes to live as long as possible. Inside this room the ultra-hard walls, floor and ceiling are all at non-right angles to each other -- so a single hand-clap can echo for up to 30 seconds. NPL uses this room to measure how acoustic materials (such as workplace soundproofing) absorb and reduce noise.
<img src="http://cdni.wired.co.uk/309x428/s_v/SMART-Testing-Range.jpg" alt="SMART antenna testing range"/>
5. SMART antenna testing range
The “Small Antenna Radiated Testing” room measures signals from antennae used for wireless communications. These include smaller devices, such as GSM and 3G antennae in mobile phones.
<img src="http://cdni.wired.co.uk/309x428/g_j/Goniospectroradiometer.jpg" alt="Goniospectroradiometer"/>
6. Goniospectroradiometer
The name literally means “an instrument that measures emitted spectra of light as a function of an angle”. It comprises a spectrometer and a series of rotary stages, and gives NPL the ability to measure the intensity and quality of a light source, whether it’s a candle, a Navy spotlight or a new fluorescent tube. Lighting manufacturers use it to produce more energy efficient bulbs.
This article was originally published by WIRED UK
