mll@hpfcso.FC.HP.COM (Mark Luce) (05/04/91)
/ hpfcso:sci.misc / mll@hpfcso.FC.HP.COM (Mark Luce) / 4:53 pm May 3, 1991 /
Sonar: Bats vs. Dolphins vs. Humans
I am interested in any comparisons of the sonar capabilities of bats,
dolphins, and humans (human technology, of course!). In particular, I have
heard the claim that bats and/or dolphins have certain sonar capabilities
which we have not as yet been able to duplicate technologically. Is there
any truth to this, or is this just another modern folk myth?
----------rowe@pender.ee.upenn.edu (Mickey Rowe) (05/11/91)
In article <9560004@hpfcso.FC.HP.COM> mll@hpfcso.FC.HP.COM (Mark Luce) writes: > Sonar: Bats vs. Dolphins vs. Humans > > In particular, I have >heard the claim that bats and/or dolphins have certain sonar capabilities >which we have not as yet been able to duplicate technologically. Is there >any truth to this, or is this just another modern folk myth? >---------- I'm not all that aware of research in cetacean echolocation, but a couple of names that you could look into to find out about bats are N. (Nabuo?) Suga, and Jim Simmons. Simmons is probably more along the lines of what you are looking for, but if you look through the reference lists of papers by Suga you may find other authors that have written articles that might interest you. There was also an article in Natural History about 2-3 years ago that discussed the history of how bat sonar was discovered. It was pretty interesting reading. As for bats doing things that we can't do, I don't know. Jim Simmons has been quoted quite often as having demonstrated that bats can distinguish the arrival of a sound at each ear when the separation of that arrival is only 10 nanoseconds! (That's one hundredth of a millionth of a second...) and that this corresponds to them using their sonar to recogize the hairs on the legs of a moth (something on the order of a micrometer). I wouldn't be at all surprised if it's true that we don't manufacture devices with that type of resolution, but I'd be hesitant to suggest that that's because we can't. I hope that someone can tell me if this has been accomplished or not, but back in the mid-80's I heard talk that PET scanners were being produced with sophisticated enough electronics to measure the difference in arrival times of photons arising from a single annihilation event. For a scanner 1 meter in diameter, that would require a resolution down to a nanosecond or less in order to be of any use. Mickey Rowe (rowe@pender.ee.upenn.edu) P.S. When talking to Walter Heiligenberg (a person who studies electric fish--another system with incredibly accurate timing) about Jim Simmons work, he told a group of us that back in the late '40s a group of people studying crickets disovered that the joint receptors in their legs can measure displacements down to around 10 angstroms (that's one nanometer!). Since that seemed so fantastic, they brought in Heisenberg--yes, I'm certain :) to check out their equipment, and he couldn't find anything wrong with it. Yes, biology is impressive.
davidh@uhunix1.uhcc.Hawaii.Edu (David A. Helweg) (05/12/91)
In article <9560004@hpfcso.FC.HP.COM> mll@hpfcso.FC.HP.COM (Mark Luce) writes: >/ hpfcso:sci.misc / mll@hpfcso.FC.HP.COM (Mark Luce) / 4:53 pm May 3, 1991 / > Sonar: Bats vs. Dolphins vs. Humans > > I am interested in any comparisons of the sonar capabilities of bats, >dolphins, and humans (human technology, of course!). In particular, I have >heard the claim that bats and/or dolphins have certain sonar capabilities >which we have not as yet been able to duplicate technologically. Is there >any truth to this, or is this just another modern folk myth? >---------- Current knowledge of bat echolocation indicates that bats can resolve differ- ences in timing (temporal resolution) down around 10 ns, a distance of about .35 microns. The temporal discrimination abilitites of echolocating dolphins is currently thought to be about 50 ns, which corresponds to about .31 microns in salt water. We human beings certainly have invented acoustic equipment that is capable of operating at such high speeds (such as multi-gigaHz sampling with digital oscilloscopes). Currently, however, I think that our SONAR capabil- ities _are_ limited. I don't know much about SONAR systems and I'd bet the engineers who work with stuff like side-scan SONAR would take issue with my assertion. Right now, our SONAR applications have only required coarse resolu- tion. I recommend three (big) books that deal with all aspects of echolocation and animal SONAR. Busnel, R-G. & Fish, J.F. (eds.) 1980. Animal Sonar Systems. NATO Advanced Study Institutes Series Vol. 28. New York: Plenum Press. Nachtigall, P.E. & Moore, P.W.B. (eds.) 1988. Animal Sonar: Processes and Performance. NATO Advanced Study Institutes Series Vol 156. New York: Plenum Press. Thomas, J.A. & Kastelein, R.A. (eds.) 1991. Sensory Abilities of Cetaceans: Laboratory and Field Evidence. NATO ASI Series Vol. 196. New York: Plenum. --- these volumes contain an enormous amount of information both about bat and dolphin echolocation. One of the most interesting things to us dolphin echolocation researchers is the _difference_ between the performance of bats and dolphins, set up in part by the 4-fold increase in speed of sound from air to water, and in part by the ecology of the different taxa.