One of the most remarkable discoveries of modern times has been the development of long-range scanning devices like radar and sonar. The Air Force and the Navy, as constituted today, could not exist without them. By electronically analyzing the echoes which are bounced off of objects in the sky (radar) or from objects in the ocean ("active" sonar), the location, movement, and characteristics of these objects can be determined. Although the basic principle of reflected echoes is the same for both, radar makes use of radio echoes and sonar of sonic or ultrasonic echoes. The development of sonar (sound navigation ranging) was necessitated by the fact that radar (radio detecting and ranging) will not work beneath the surface of the water.Today, all large vessels and many smaller ones are equipped with echo sounders or fathometers which beam sonar pulses downward to measure the depth of the water beneath the hull. The echo sounder thus takes the place of the sounding lead. Commercial fishermen locate schools of fishes by the ultrasonic vibrations which are reflected from the fishes' bodies. A submarine navigating beneath the polar ice cap determines by sonar not only (i) the distance and contour of the bottom but also (ii) the amount of free water between the top of the vessel and the ice above it and (iii) the presence of reefs, submerged mountains, or other obstacles in a horizontal plane. AUGUST 1962 Echo Ranging in AnimalsBut these electronic ma and sonar are matched passed by the echo ranj perception of such anim. and the bottlenose dolphiJ Bats catch night-flying i; wing by listening to the e own rapidly repeated ci unique method of distan in the bat was originally Spallanzani as far back Within the last decade or been determined that t dolphin-and probably toothed whales as well-r ocean by emitting trains underwater sonic pulses ( may be able to distinguish from another by this meth nocturnal birds (4), and laboratory rats (5), empl ing to some degree for space. Thomas C. Poulte ford Research Institute found that the California trains of echo-ranging sig of the bottlenose dolphinIn the light of all this prising that human bein superior neural and senso make so little use of so daily life. In fact, echoc considered to be a hin than an asset in auditoi and when they are note4 are often the cause of spe SCIENCE In acoustical engineering great emphasis is placed on designing rooms and wall surfaces which are "anechoic"-that is to say, which reflect few if any echoes. A blind man tapping with a cane-and hence producing a regular sequence of sound pulses-is probably the closest l.g human analogue to the remarkable sonar systems of the porpoise and the bat. With some embarrassment, I quote here a recent statement of my own on this subject (3, p. 48): "the avoidance gg of objects by the blind appears to be very crude when compared to the precise auditory perception of which bats are capable." The present article gives newly obtained data in partial refutation of this statement. It shows just how irvels of radar accurat...

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