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Hadrosaur vocalizations and predator hearing
I have some questions for my Grade 9 Science Fair Project.
1. I've now read in several places that parasaurolophus was able to produce
vocalizations at a frequency of about 10 Hz. For an example, see
http://www.abqjournal.com/fleck/fleck1.htm With my PVC model, I am unable
to produce resonance below a frequency of 50 Hz. What am I missing?
2. In a hadrosaur, what was the diameter of the Eustachion tube? Could it
have carried enough sound energy to allow the animal to use the nasal crest
as a resonator for hearing?
3. I'm thinking of building a model of a theropod ear. Would the rubber
from a balloon give a good simulation of an ear drum?
4. I the following book, I read,"The general rule is that to be most
effective, loudspeakers and the mouths of trumpets should have diameters of
at least one-sixth of the wavelength of the sound. ... Parasaurolophus
should ideally have had nostrils flaring out like the mouths of trumpets 70
centimeters in diameter." --- p. 88 Alexander 1989. Dynamics of Dinosaurs of
Other Extinct Giants. Columbia University Press, New York
Could Parasaurolophus have gotten around this limitation by opening its mouth?
5. After I asked for comments about my project summary, Dr. Jason J. Head
of Southern Methodist University sent a message in which he made the
a) A keen sense of smell would make it unnecessary for a predator to hear
the vocalizations of its prey. "Hadrosaurs, as multi-ton herbivores,
probably gave off quite a stink, especially if they were herding (ever
driven past a cattle farm?), and several hundred hadrosaurs would probably
be smelled before they were heard."
b) A herd of animals makes so much noise that there is no point in
worrying about specific frequencies.
c) Low frequencies are difficult to locate. "Songbirds use low notes as
predator warnings- the source of higher frequencey sounds is much easier to
locate than low- something we experience every day. These low notes alert
other members of the flock while protecting the "warner" from being located."
Do I have to change my hypothesis again or is there someone out there who
can counter these arguments?