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Re: Dino Vocalizations: My Previous Attachment

drury@agt.net wrote:

> Hypothesis:  Hadrosaurs used their crests as resonance chambers to produce
> low frequency vocalizations which their predators could not hear.

Wouldn't this have been of limited utility? I believe the physics 
says the low-frequency emissions would be hard to directionally 
localize since multiple detectors have to be spaced at a good 
fraction of the wavelength, at least, ie the detector has to be
comparable in size to the (folded)generator. This is maybe problematic
using only ears. I recall that the lower frequency range 
of human direction finding is comparatively high, in the 100s of Hz. 

Just shouting "Predator here!" doesn't help much, if other non-local
hadrosaurs can't localize the direction to determine which way
to flee (or rally for defense?!)

Worth thinking about, IMHO.

[ You might want to keep in mind that making noises predators can't
  hear is likely to be quite separate from making alarm calls.  An
  animal is better off if its predators *can* hear alarm calls because
  said calls tell the predator that he's been spotted.  Predators are
  less likely to pursue prey if they "know" they've been detected and
  are thus in for a chase.  As potential prey, you want to make noises
  your predators can't hear when those noises serve purposes other
  than alerting your neighbors of a predator, however. -- MR ]

Russ Andersson

PS:There's some analysis of vocalization pitch in "Dynamics of Dinosaurs
and Other Extinct Giants," R. McNeill Alexander, Columbia University
Press, 1989, in Barnes and Nobles everywhere.