INDEX 



Buoys, 58 



Buddenbrock, W. von, 147 



Burglar alarms, 51 



California, 21 



Cancellation, 44 



Carthy, J. D., 148 



Cathode-ray oscilloscope, 60 



Chirping bats, 87 



Chirps, 87 



Clickers, 65-69, 72-73, 74-77; 

 and echoes, 66-69; fre- 

 quency ranges, 76 



Communication, 19 



Constant frequency pulses, 

 116 



Constructive interference, 44, 

 48 



Cornell University, 132 



Cosmic rays, 35 



Cotzin, Milton, 132, 133, 143 



Creaking, 22, 23 



Dallenbach, Karl M., 132, 



133, 143 

 Darkness, 17, 27 

 David, Jr., E. E., 149 

 Dead spots, 50 

 Deafness, 148 

 Deep scattering layers, 110 

 Destructive interference, 44 

 Dijkgraaf, Sven, 31 

 Doppler effect, 113-16, 149 

 Duty cycle, 126-27 



Ears, 36; bats, 28; human, 29, 

 45, 64, 107, 134, 147; inner 

 mechanism, 19. See also 

 Hearing 



Earthquakes, 117; seismic 

 waves, 116-17, 119 



Echo detecting equipment, 36, 

 107 



Echoes, 10, 24, 44, 52, 56, 

 148; acoustics of, 57-73; 

 concentration of, 75-77; de- 

 emphasized, 64; definition, 

 44; devices, 65-69, 70-73, 

 74-77, 107; effects of, 47; 

 experiments, 65-69; func- 

 tion, 45; magnitude, 61, 63; 

 masked, 59; multiple, 113; 

 objects, 73, small, 78-80; in 

 prospecting, 116; reflections, 

 75-77; return, timing, 73; 

 scattered, 70; suppression, 

 64-65; types, 81; use of, 10, 

 17, 29, 58, 116 



Echo experts: in air, 26-32; 

 in water, 18-26 



Echolocating equipment, 36, 

 107 



Echolocation, 21, 81, 149; in 

 air, 108; bats, 29, 78, 90- 

 95, 99-100, 112; blind 

 people, 148; definition, 18; 

 devices for, 58; discrimina- 

 tion problem, 119-20; fish- 

 catching, 95-99; moving 

 vehicle, 77-78; obstacles, 

 31; oil prospecting, 117; 

 outer space, 108; porpoises, 

 22-26; underwater, 108; 

 warnings, 73. See also Ob- 

 stacle detection 



"Echo-Location for the Blind," 

 150 



Echo sounders, 58, 109; value 

 of, 110-11 



Eggers, Friedrich, 54, 55, 56 



Electromagnetic waves, use 

 of, 107-8 



Electronic equipment, 10 



Electronic hearing equipment, 

 30 



Electronics, 149, 150 



Electronic sonar, 149 



Energy source, 149 



152 



