Sunday, 8 April 2012

Echolocation vs. the Quietest Place on Earth

I read a news article this week about an ‘anechoic chamber’* at Orfield Laboratories in North America. The Guinness World Records have declared it “the quietest place on Earth”, for its ability to absorb 99.9% of sound.

The chamber is surrounded by 1m thick fiberglass acoustic wedges, has double walls of insulated steel and 30cm thick concrete (see picture above). According to Steven Orfield, the longest anybody has been able to sit in the darkened chamber was 45mins.

In the dark, it’s so quiet that the occupant becomes the sound, hearing only their body (i.e. heart beating, lungs breathing). Apparently this is a very disorientating experience, so much so that the occupant must be seated.

Mr Orfield said, “How you orient yourself is through sounds you hear when you walk. In the anechoic chamber, you don't have any cues. You take away the perceptual cues that allow you to balance and manoeuvre. If you're in there for half an hour, you have to be in a chair.” As a unilateral, hard of hearing person, I found this statement to be very interesting.

NASA has a similar chamber which they can put a water tank in to ascertain how long it takes before an astronaut starts to hallucinate, or whether they could even work in such an environment. The chamber absorbs electromagnetic energy to simulate the open space environment. Space is like a giant anechoic chamber.

This got me thinking about the connection between our hearing and our orientation in the environment around us. Our inner ear consists of a cochlea (which picks up sound), the labyrinth (semi-circular canals that perceives rotational movements), and the otolithic organs (which transduce linear accelerations). It’s interesting that the cochlea contributes to orientation in so much that that the brain uses sound to support other orientation inputs (Vestibular system, Somatosensory system of proprioception & kinesthesia, Vision). I suppose that’s the reason the inner ear is connected the way that it is.

This reminded me of a teenager I had heard about years ago named Ben Underwood**. Ben, who became blind weeks before his third birthday, had an amazing ability to use echolocation to ‘see’ his environment. Echolocation is the ability to detect the surrounding environment by sensing echoes bouncing off objects.
By clicking his tongue, Ben was able to hear the distinctive echoes around him. One of Ben’s observations was that “people sound just like the surface of water” (which would make sense considering the human body averages approx. 60% water). He became so good at using echolocation that he was able to ride a bike, rollerblade, play video games, try karate and even surf waves.

Even though a sighted person wouldn’t use the clicking technique employed by Ben, they would still rely on their hearing to navigate as demonstrated in the darkened anechoic chamber.

*Anechoic: Neither having nor producing echoes.
**Unfortunately Ben passed away in 2009 from a brain tumour just before his seventeenth birthday. He lived a remarkable life in a short time and still inspires others today.


Read more about The Quietest Place on Earth here:

Read more about Ben’s Echolocation here:

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