By Marcus Wilson 07/02/2017 3

I have been rather conscious of my looonnnnggggg absence from the blogosphere.

That really is down to other commitments getting in the way, and then falling out of the habit of blogging.  Hopefully this will be a restart. I have a good opportunity here – I have just started a period of study leave (what used to be called Sabbatical in the old days) and arrived this week in Perth, where I’m visiting the University of Western Australia. I’ll be here for nine weeks – a fantastic chance not to be interrupted by people knocking on my door (and, yes, to develop some research ideas too, I should add).

So, first stop, naturally enough when you have a four-year old, is the local playground. And what a playground it is too. It’s been set-up to blend in with the trees and it works really well. It also includes a neat bit of physics.


It’s a telephone, as in ‘tele’ (long distance transmission) and ‘phone’ (voice).  Now, the long distance here is only about 10 metres, but it’s still quite impressive that it works. The sound waves head down the pipe that you see in the photo, under the ground, then up to an equivalent speaker/microphone across the path. The set up works really well. What we basically have is a broadband acoustic transmission line. Since the pipe is heavy and stiff, the sound waves in the air in the pipe reflect off the sides without too much loss of intensity and out the end. Rather like an optical fibre does for light.

What would be really useful is to add some splitters, directional couplers, multiplexers and the like, which would turn it into something more akin to a modern telephone system and transmit to various different locations. That’s one thing that is easier done with electricity or light .  One of my PhD students is working on acoustic network analyzers – that’s a solved problem with electromagnetic waves but it’s not so easy with sound waves, as we’re learning.

More Perth physics to follow. Watch this space.

3 Responses to “Physicsstop back in business”

  • Glad to have you back Marcus. I’ve missed your Physics Stop posts, I always find them interesting.

  • Cool, remove the pipes and use electricity and you have Nathan Stubblefield’s “first mobile phone”.
    Nathan Stubblefield’s was passing electricity through the earth , this was coupled to sound and was able to be transmitted and received without wires through the earth. Little known friend of Nicola Tesla

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