Sunday, 27 February 2011

Anechoic Chambers

An anechoic chamber is a room with special walls that absorb as much sound as possible; anechoic means "without echoes". Sometimes the entire room even rests on shock absorbers, negating any vibration from the rest of the building or the outside.

The material covering the walls of an anechoic chamber uses wedge-shaped panels to dissipate as much audio energy as possible before reflecting it away. Their special shape reflects energy into the apex of the wedge, dissipating it as vibrations in the material rather than the air. Anechoic chambers are frequently used for testing microphones, measuring the precise acoustic properties of various instruments, determining exactly how much energy is transferred in electro-acoustic devices, and performing delicate psychoacoustic experiments.

The world's first wedge-based anechoic chamber was built in 1940 on Murray Hill, at Bell Labs in New Jersey. It is encased in more than a meter of concrete to shield it from external noise. Its creators have boasted that the chamber absorbs over 99.995% of the incident acoustic energy above 200 Hz. The wedge-shaped panels are poor at absorbing lower frequencies, but these frequencies carry little energy and are inaudible to human ears. At one point, the Murray Hill chamber received the Guinness Book of World Records' award for being the world's quietest room.

John Cage, a famous experimental composer, was inspired when he entered Harvard's anechoic chamber in the 1940s and heard the sound of his own blood circulating. He ended up composing a three-minute piece that consisted of nothing but silence, to allow audiences to reflect on the reality that no person has yet been able to escape noise entirely -- except presumably the deaf.

According to Guinness World Records, 2005, Orfield Laboratory's NIST certified Eckel Industries-designed anechoic chamber is now the quietest place on earth measured at −9.4 dBA. The human ear can typically detect sounds above 0 dB, so a human in such a chamber would perceive the surroundings as devoid of sound.

The University of Salford has a number of Anechoic chambers, of which one is unofficially the quietest in the world with a measurement of −12.4 dBA.

I would really like to try one of these chambers out, but there's a rather disturbing description of someone trying one out at this bog:

Then again, maybe I could start out with something a whole lot more relaxing - a floatarium!


Lesley Punton said...

they are truly weird and rather unsettling. In the old girls high school building (where I had a studio on the MFA - now "luxury" flats on garnethill st) there was an old, language lab (great term in itself) tucked away in the basement where nobody ever went. The effect of silence in the space was entirely oppressive. Quite how they thought having schoolgirls cooped up in this was any good, I don't know. They all probably hate the French language to this day.

For a slightly less oppressive experience, try the sound booth in EMS where the reverb is vastly reduced for clarity of sound recording.

Failing that, eat lots of eggs and decorate the walls of your house in eggboxes!

M-J Archibald said...

Lol, very art student thing to do!! I might try it although will have to get Paul and the girls eating eggs too!

Actually, I think the sound booth is a great idea - I might pursue that one. Also, have you come to the bit in the Sarah Maitland book about the reaction of the prisoners to the silence? I thought that was really interesting, especially as in one article I read, someone had become very frightened in one of these chambers, because of what she could/couldn't hear. I think the idea of being afraid of silence is really interesting...

Again, sorry for being so slow in my response!

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