Now, can we train birds to geolocate to the nearest 0.04' ?
Derek
--------------------
and from:
The Friday Fillip: In One Ear
Posted: 08 Feb 2013 04:00 AM PST
The Economist reports on pigeons. At least it does when they're unable to find their way back home in upstate New York. Seems homing pigeons, long a marvel to the geolocation folks, have trouble with their animus revertendi, as we ex property profs like to say, when it's animated near Jersey Hill, NY. And this, we learn from "The Birdmuda Triangle," provided the anomaly that led biologist Bill Keeton to figure out a third piece in the puzzle that is pigeon homing. Scientists have known about the birds' ability to use the sun and the Earth's magnetic field for navigation. Now they know that these unprepossessing creatures can also hear the ocean, using the infrasound rumble of the waves — hundreds of miles away — to help them orient themselves. (For a much more thorough exploration of this phenomenon, see "Pigeons seeing with sound: the perception of infrasound" by Keeton himself in cerebrovortex.)
It can be a bit disorienting to realize that there's a whole lot going on that we never hear, disorienting and humbling. What poor animal royalty we are, when we can't hear the ocean as well as an annoying messy bird. Or when our shouts can only be heard a few metres away. Elephants, for instance, can "sing" notes far below the range of our voice boxes and our hearing that, like other low-frequency long-wave sounds, can roll for kilometres. For that matter, whales can send their infra- grumbling half way round the world.
Human beings are pretty much stuck between 20 and 20,000 Hertz when it comes to hearing — and most of us can't even manage that range, our ability falling off as the Hertz rise. We shouldn't get too fussed about it, though, because much, if not most, of the numbers at the high end are the result of repeated doubling, the top tip, as it were, of the exponential curve. As the Naxos blog puts it:
If you wanted to make a piano covering the entire range of human hearing, you’d need to give it 120 keys instead of the normal 88. If, halfway through building it, you decided you only wanted it to go up to 10,000Hz, not 20,000Hz, you wouldn’t remove half the keys. You’d only remove 12 of them . . .
That same blog post has a sound test you can take to see where your upper range quits, a 30-second launch from 20Hz up to 20,000Hz. (Not saying where I fell away, but it was further up the ladder than I'd feared.)
As for the bottom of the range and just below it, i.e. at the border of infrasound, I suggest you get a fine recording of Strauss's tone poem Also Sprach Zarathustra (the music used at the beginning of the movie 2001, A Space Odyssey) and listen to it with a very good pair of earphones (or better still, go listen to a good live performance). The opening note should be performed on the lowest (pedal) note of a big pipe organ, which is a bottom C that has a frequency of 16Hz — music you may not be able to hear but that you might feel anyway.
But fretting about limitations like this is silly. There are, after all, only twelve tones in the current western musical scale, and yet the variety of music that emerges is almost limitless. And, too, nature is kind enough to broadcast most of its chatter within our range. Check it out at Cornell's Macaulay Library, "the world's largest and oldest scientific archive of biodiversity audio and video recordings." Here you'll find field recordings of the snipe, the surprising walrus (who does not "coo coo ca choo"), the common virtuoso katydid, and hundreds of others as well, including, of course, the rather more familiar sound of the homing pigeon, a.k.a. rock dove and Columba livia domestica.
And as for finding our way home, well, "there's a map for that."
