Part 3: The Wall Talks Back

Fact: Walls are great listeners.

Like talking to a brick wall – a classic phrase to describe someone so stubborn they simply refuse to hear what you’re saying.

But what if I told you we’ve got that all wrong? To prove a point, take this experiment performed on the Berlin wall. A kind old man is reading a story directly to one side of the wall, but his audience – a class of schoolchildren – are on the other side of no-man’s-land. Five minutes later they were clapping and cheering – they heard every word.

How? By the magic of science. As their name suggests, accelerometers are electronic devices that detect acceleration. They’re how your phone knows when you turn it upside down, but in industry they’re used to detect tiny vibrations in sensitive equipment, like jet engines, to give advanced warning of any potential malfunctions.

Sound waves are vibrations in the air, but sound can travel through liquids and solids too by making them vibrate in the same way. When the sound waves of the old man’s story hit the solid wall, those vibrations were passed into the wall itself. The accelerometers picked up those vibrations: the signal was then decoded and passed to a set of speakers on the other side of no-man’s-land, where the children were eagerly awaiting their story about a family of cats.

The kids were literally hearing what the wall was hearing, and the story came through crystal clear. So it turns out that walls are great listeners. Makes that stubborn person in your life all the more frustrating.

This series of posts is based on the General Electric ‘Unimpossible’ video series currently on Youtube – check it out, its awesome:

‘Another one of Mr Shaunak’s Little Bites of Science’
Image under Creative Commons license

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