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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
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
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.
From: firstname.lastname@example.org [SMTP:email@example.com]
Sent: Monday, January 20, 1997 8:27 PM
Subject: Re: Gr. 9 Sc: Pesky Harmonics
>I have received an off-line message from Mr. Hernan Toro of the
>Pontificia Bolivariana in which the following points are made. Dr. Toro
>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
>would be detected by predators. However, it is possible that these
>frequencies would be dampened by the lining so that predators could not
>them after all.
Why might the predators be unable to hear the low frequency
"The more television I watch, the more I wonder why I'm not already
supreme ruler of earth." --Dogbert