Acoustics ‘R’ Fun: the sound of two hands clapping

I found The Sound Book at Kramerbooks in Washington D.C.’s DuPont Circle, a real bookstore that has almost a whole wall dedicated to books about science. Like a kid in a candy shop, I picked a few likely suspects and rushed to the train to start reading. The Sound Book is now thoroughly scribbled in, dog-eared, highlighted, and sticky-noted, with a few coffee stains on the front cover. In short….a good read.

Trevor Cox is a professor of acoustic engineering at the University of Salford in Manchester, England. The book opens with his hunt for the world’s most reverberant space (this is what acousticians do for fun, when they’re not hand-clapping and balloon-popping in front of buildings and staircases). His search takes him (and the reader) to cathedrals, water cisterns, caves, and a mausoleum, all with some pretty impressive echoes. Eventually, he finds the winner — an oil storage complex at Inchindown, Scotland. It was constructed deep into a hillside during WWII to secret away 144 million liters of fuel – enough, he writes, “to fill up two and a half million diesel cars.” Okay – big. And empty (now). He has to squeeze through an old pipeline to get into the space — an option most of the others in his group are too claustrophobic to even attempt.

As he prepares to take reverberation measurements with his laptop, it has other ideas, deciding this would be the perfect time to update its Windows operating system. So he and his colleague, archaeological investigator Allan Kilpatrick, revert to the old-fashioned (but still valid) analog approach – firing a pistol (with blanks) and recording the echoes. The result was a mid-frequency reverberation time of 30 seconds, broadband time of 75 seconds, and high-frequency time of almost 2 minutes. We have a winner!

That does sound like fun, right?

If it does, this is a great book for you. I was surprised at how much I enjoyed going along on Cox’s explorations. You also get to join him in his bathroom to measure the acoustics, debunking a claim about the speech-enhancing properties of a Neolithic burial chamber (which are very similar to those of his bathroom).

So, my advice is to give it a shot…with blanks.

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