INDEX 



Listening in the Dark, 10, 25, 

 99, 104, 148 



Man's World of Sound, 149 



Marine animals, 110 



Marine aquaria, 21 



Marine mammals: sounds, 21. 

 See Porpoises and Whales 



Massachusetts Institute of 

 Technology, Radiation Lab- 

 oratory, 149 



Maxim, Hiram, 108, 109 



Mental telepathy, 137 



Metronome, 75 



M.I.T. See Massachusetts In- 

 stitute of Technology 



"Modern Sonar Systems," 

 149 



Moehres, Franz P., 84 



Molecules, 9, 19, 39, 40, 50, 

 119 



Moon, 120; echoes, 147 



"More about bat 'radar,' " 148 



Multiple echoes, 113 



Music, 49, 50 



Musical instruments, 49 



Natural selection, 104 

 Natural sonar, 148 

 Navigation, 2, 58; of animals, 



148; bats, 2, 27, 32, 108; 



radar, 147 

 Neutrinos, 35 

 Nuclear explosions, 117 



Obstacle detection, 31, 132- 

 40; ears, 134-35; echoes, 

 138-40; skin, 133-34; 

 sound, 136-40. See also 

 Echolocation 



Obstacles: for bats, 93; wires, 

 100-1 



Oceanography, 147 



Oceanography and Marine 



Biology, 147 

 Oceans, 109; deep scattering 



layers, 110; depth, 19, 40, 



147; false bottoms, 110, 



116, 117 

 Orientation, 10, 19, 27, 148 

 Orientation sounds, 84-87, 



148; air to water, 97; bats, 



2, 29-31, 84-87, 89-90, 



97-98; frequencies, 84-87; 



obstacles, 93-95; porpoises, 



22-26 

 Outer space, 9, 120, 147 

 Oscilloscope, 60; screens, 120, 



122 

 Owls, 27 



Parabolic horn, 70-73 



Pavia, 27 



Physical Science Study Com- 

 mittee, 7, 8, 10 



Physics, 10 



Piano, 49 



Pierce, G. W., 2, 29 



Pierce, J. R., 149 



Pinging, 112 



Plants, 9 



Porpoises, 18, 20-26, 44; 

 brains, 20; creaking, 22, 23; 

 echolocation, 22-26, 99; 

 hearing apparatus, 24; lan- 

 guage, 21; objects, small, 

 104; Schevill experiment, 

 22-24; sonar, 148; sounds, 

 21, 22, frequency range of, 

 25-26 



Probing signals, 18, 22, 23, 

 112 



Psychology, 10 



Radar, 18, 107-8, 120-27, 

 149; uses of, 120; wave 

 length, 121 



154 



