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A few odds and ends
"Lawrence Akins" <firstname.lastname@example.org> wrote of the supersonic
> I like that theory, but don't really agree with it. I think the
> Sauropods would need good ears as well.
[ ... ]
> So wouldn't the crack hurt their ears as well?
I don't think this is a very realistic concern. We're talking about
biological organisms here and they're exquisitely good at solving this
sort of problem. Think about echolocating bats -- their ears have to
be sensitive to the sounds that they emit because they're listening
for the return echoes which are just lower intensity reflections of
the same sounds. To get a decent echo they have to broadcast with a
lot of power. When they're emitting they relax their middle ear
muscles to decrease the sensitivity of their ears. Although I'm not
saying saurpods would have had a similar adaptation (irrespective of
whether or not they had the whip-cracking tails) there's no reason to
suggest that they couldn't have some such adaptation for protecting
themselves from their own "emissions".
and on Parasaurolophus modeling, Scott McCray
<email@example.com> wrote (quoting William Monteleone):
] ] People have been making replicas of Parasaurolophus crests and
] ] trumpeting into them for a couple of years now. But has anyone stopped
] ] to think that we're still missing the soft tissues which made the
] ] sounds? Garbage in Garbage out.
] In a word, yes. I believe that it has been acknoleged that the
] sound produced would have been influenced by soft tissue to a small
] extent. However, the soft tissue is not what makes a resonance chamber
] work. Further comments below.
I have to agree with Scott on the word "yes" -- I recommend you search
the archives of this list since a few of us discussed the subject here
in the Spring of '95 (IIRC).
] Most of the sound qualities associated with resonance chambers
] are determined by the lengths and diameters of the chambers (the
] tubing involved). The musician (or Parasaurolophus) can manipulate
] the sound only by varying the speed at which air is passed through
] the chamber or by altering the pressure at which it's introduced.
] In truth, this only changes the notes played, not the pitch or
] timbre of the sound produced.
In our previous conversation on the subject another participant used
the word "note" in a way that seemed odd to me also. What do you mean
by "note"? The "notes" in written music correspond to pitches, but
that doesn't seem to be how you're using the word here. To the extent
that I understand you, though, I think I disagree with you. I'd ask
that you check the archives, though, since I think most of my
disagreement is already spelled out there.
And I'll also add something that a colleague of mine here at IU wrote
to Della Drury when I asked him to comment about the soft tissue
problems (he works with sound production in birds):
} Your project is an interesting one but you can't get enough
} data about the vocal track from fossils to get a meaningful answer.
} You cant assume for example that the dimensions of a chamber tell
} you the frequency of the sound in the vocalization. Depending on
} the entire tract including the location of the vocal organ, the
} position of the tongue etc the vocal tract may or may not be tuned
} to a particular resonant frequency. Also portions of the tract may
} function to filter out sound at their resonant frequency rather than
} transmit it. This is the case in certain echolocating bats in which
} the nasal cavities filter out the fundamental frequency (which is
} their resonant frequency) so the vocalization consists of the second
} harmonic without the fundamental.
} Your elephant question is an interesting one to which I don't
} know the answer. The trunk might act as tube stopped at both ends
} and resonate at a quarter wavelength as you suggest. A relatively
} modest change in the diameter of the air passage inside the trunk
} could have a large effect on the resonant properties. The acoustics
} of vocal tracts are so complicated that even in living animals where
} one can do accurate measurements and experimental manipulations they
} are often difficult to understand or predict the acoustic output.
} My guess is that the elephant trunk resonance is an untested
} hypothesis and that whatever the trunk does depends on complex
} interactions with nasal, oral and respiratory cavities.
In other matters, Bill Adlam <firstname.lastname@example.org> asks about
) Wouldn't asymmetrical feathers be just as useful for hydrodynamics
) as they are for aerodynamics? Anyone know if penguin feathers are
I think that penguin feathers are symmetrical (but don't quote me on
that). However, it doesn't much matter since their feathers don't act
as part of an airfoil the way that the flight feathers of flying birds
do. Lift isn't so important when you're traveling through a medium
that's about the same density as you are.
And for the last bit of lunacy, ETHEREDM <ETHEREDM@aol.com> asks:
| IS ANYBODY OUT THERE? I think that Earth once had two moons, both
| approximatly 10-15 miles in diameter.
I heartily recommend you find a copy of:
Age and Origin of the Moon
_Science_ 1997 November 7; 278 (5340):1098 (in Research
Articles) D. Lee, A. N. Halliday, G. A. Snyder, L. A. Taylor
Mickey Rowe (email@example.com)