November / December 2020

Editor's Lead In
Subwoofers, Earthworms, And Ig Nobles
Editorial By Greg Borrowman

  I am a great fan of active subwoofers. That in itself is a curious sentence, because many years ago, I would have started this column with the sentence 'I am a great fan of active and passive subwoofers' or, perhaps, just 'I am a great fan of subwoofers.' I say this because back in the day before digital signal processing was easily available, the performance of active and passive subwoofers was identical, assuming all components were equal. The only difference was that an active subwoofer had the amplifier inside the cabinet, while a passive subwoofer meant you had to provide an external amplifier. DSP moved the goalposts because subwoofer designers could use electronic equalisation to modify the performance of the driving amplifier to extract maximum possible performance from the driver, while at the same time ensuring protective circuits were in place to prevent damage to either. You can't do that with a passive subwoofer.

Anyway, I am a great fan because I don't think there's any better way to deliver the lowest musical octave, which is 16.35Hz to 32.7Hz (or if, you'd prefer it in tempered scale, C0 to C1) in a domestic living room. Yes, it can be done using floor-standing speakers, but to do so requires engineering overkill that's the equivalent of using a sledge-hammer to crack a walnut, plus you're using two cabinets (and multiple drivers) to do it, when bass at these frequencies cannot be localised by the human ear, so only a single cabinet is required, and one large driver, plus a DSP-controlled high-power amplifier, can do the job perfectly well. Just as an aside, 'middle C' is C4 (261.63Hz), the highest C on a piano is C8 (4186.01Hz) and the limit of hearing for most male adults over the age of 40 is C10 (16744.04Hz). C0 to C10 is ten octaves. 20Hz to 20kHz is also ten octaves. (Please don't send me any e-mails about these hearing limits—I know there are exceptions, so just be pleased that you are one of them.)

Anyway (again), it appears that two Victorian-based researchers, Ivan Maksymov and Andriy Pototsky, are also great fans of subwoofers, because one of them recently helped them win a prestigious Ig Nobel prize. I am not sure if 'prestigious' can be used in relation to the Ig Nobel, because these satiric prizes are given to publicise unusual or trivial achievements in scientific research, with the aim being "to honour achievements that first make people laugh, and then make them think." Maky and Potsy won this year's prize by placing earthworms (three varieties) on top of a subwoofer, then running sine waves at sufficiently high sound pressure levels (in a garage, so as not to annoy the neighbours, though as this was in Seymour, in regional Victoria, any neighbours would have been a long way away) through it to make the worms wiggle. The two discovered that various different frequencies caused the worms to form patterns inside their bodies in the same way that water droplets react to vibrations (YouTube has dozens of videos of this phenomenon).

Lest you think their worm-wiggling experiment was weird, please note that this year's overall Ig Noble winner was an American anthropologist who made a knife from his frozen faeces in order to cut a pigskin with the 'blade' (the attempt failed). And lest you wonder about the real point of the Ig Nobles, which are awarded by Harvard University, it's that doing 'what if' research sometimes pays off. Andre Geim, who won an Ig Noble for using magnetism to levitate a frog, went on to win a Nobel prize in physics. As for their worm-wiggling research, the two Victorians believe it could be useful as a non-invasive technique to study human brain impulses.

Unlike winners of the Nobel prize, who get shed-loads of money, Ig Nobel winners receive a paper cube folded by a Nobel laureate, and a Zimbabwean 10 trillion dollar bill. And unlike Nobel prize winners, who get to give lengthy acceptance speeches, Ig Noble winners have only 60 seconds to speak, after which an eight-year-old girl is on microphone duty to enforce the one-minute rule by announcing “Please stop, I’m bored.” So I will too.

— Greg Borrowman

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