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RE: Gr. 9 Sc: Pesky Harmonics



I suspect that Dr. Toro is right to first approximation.   Your simple 
model should sound fairly close.

The main impact of the lining and soft tissues would be:

-       Influence the higher harmonics
-       If they could open or close passages that alter the length (like the 
keys 
on a bugle or trumpet) this would effect the tone.
-       Alter the way that a call begins and ends.   As an example, contracting 
the passageway could change the volume of the note.
-       Some soft tissue presumably excited the oscillation.  This is like the 
reed in a flute or other musical instrument.  Different reeds do produce 
different sounds.

I think you might want to talk to a tuba, trumpet, trombone or horn player 
(maybe your school has a band).  They are playing instruments that are 
roughly similar.  They will have more direct experience with the properties 
of sound in the context that you are talking about than those of us who are 
theorizing about this. ;-)

Also, you can always try an experiment where you try a small horn or model 
dinosaur trumpet  and line it with different things.

Many current animals that face a predation threat make vocalizations that 
their predators can hear.    It does NOT stop them from making the call.

The trick is that they do not call constantly, so the actual threat is 
fairly small.  Broadly speaking,  vocalizations are made in contexts where 
they are of more value than the risk they cause.  Thus, male elk will bugle 
during mating season - which makes the makes them easier for predators to 
localize, but the value of finding mates  is higher.   Prairie dogs will 
whistle, which is a high frequency tone that is easy to localize.  They 
primarily do this to warn of a predator coming.   This increases risk to 
the whistler, but overall it is worthwhile.

In a similar fashion, I suspect that hadrosaurs made vocalizations 
regardless of whether it attracted predators.    They probably would not do 
so constantly - just in situations where there was enough survival value 
that the made sense.

Nathan

----------
From:  brucet@mindspring.com [SMTP:brucet@mindspring.com]
Sent:  Monday, January 20, 1997 8:27 PM
To:  dinosaur@usc.edu
Subject:  Re: Gr. 9 Sc: Pesky Harmonics

>To All:
>
>I have received an off-line message from Mr. Hernan Toro of the 
Universidad
>Pontificia Bolivariana in which the following points are made.  Dr. Toro 
is
>an electronics engineer.  I have asked for, and been given, permission to
>quote from his message.  In giving permisssion Mr. Toro asked that I add:
>"Mr. Toro said they were conjectures."
>
>1.  The long wave lengths that come with low frequencies would be so much
>longer than the thickness of any lining of a hadrosaur's airway that the
>difference between the real situation and my model can be ignored.
>
>2.  Any vocalization would probably include high frequency harmonics 
which
>would be detected by predators.  However, it is possible that these 
higher
>frequencies would be dampened by the lining so that predators could not 
hear
>them after all.

        Why might the predators be unable to hear the low frequency
vocalizations?

<snippage>

bruce

        "The more television I watch, the more I wonder why I'm not already
supreme ruler of earth."  --Dogbert