SECT. 4] 



SOUND PRODUCTION BY MARINE ANIMALS 



555 



Moulton (1958) gives spectrograms and other details of sounds of fishes of 

 nine famihes, including swim-bladder drumming and dental stridulation, etc. 

 (Fig. 7 is from this paper; Fig. 8, also Moulton's, is from Backus, 1958). 



SECONDS 



Fig. 7. Sound spectrogram of tooth stridulation, hy Car anx hippos. (After Moulton, 1958.) 



UJ 



4.0 



3.0 



2.0 



I.D 



0.2 



l» f* \Up i«'t 



• }j tt P 



HHiiiiiiH 



0.4 0.8 1.2 1.6 2.0 



TIME (sec) 

 Fig. 8. Sound spectrogram of swim-bladder vibration of Prionotus sp. (By courtesy of 

 James M. Moulton, from Backus, 1958.) 



Best studied of crustacean sounds are those of the "snapping shrimp". The 

 spectrum of this noise is quite broad (about 500 c/s to 20,000 c/s), and sound- 

 pressure levels of about 0.02 dynes/cm^/one-cycle band have been observed for 

 choruses of these animals. Typical peak pressures for single snaps of Alpheus 

 and Synalpheus were about 200 dynes/cm^, with peaks to 1000, at one meter 



