There's been a lack of any activity from me for the last few weeks. This is mostly down to teaching overload at university. About 50% of my year's teaching comes in the first half of our first semester, which leaves me pretty-well no time to do anything else. Writing in a blog is the least of my priorities at the moment, I'm afraid.
That doesn't mean I'm not taking note of physics when it arises. On Monday night I was supervising a test – it was the loudest one I've ever experienced (save the 'test you can talk in'). That was down to 180 students shuffling pieces of paper about in a concrete-walled, concrete floored lecture theatre. With the sound reflected so nicely off the rigid walls (having a very different acoustic impedance from that of air) each turn-of-the page would have been heard several times before its energy finally decayed away. Couple that with a test script that in hindsight was badly formatted and required the students to keep turing to the back to look things up in a table, and there was a real hubbub of paper noise. The sign 'Quiet Please, Examination in Progress' on the door was quiet pointless.
Back some time later…