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My Gr. 9 Sc. Fair Project Summary



Dear All,

The first draft of my project summary is pasted into the end of this
message.  If you want a copy with the proper formatting contact me off line
and I will send you an attachment.  I have written it in MS Word 6.0.  I can
also save in Rich Text Format, MS-DOS Text, WordPerfect 5.0 or 5.1, Word for
Windows 2.0, or Word for Macintosh. 

As usual I have questions.

1.  Does anyone have comments on my summary?

2.  In the Journal of Vertebrate Paleontology, Sept. 19, 1996, Robert
Sullivan has written: "The crest is divided, for its entire length, by a
sagittal septum and evidence for a common medial is lacking."  I think this
says that the crest of parasaurolophus contains two separate air columns.  I
know that my face is not perfectly symmetrical.  I suspect that the air
passages in parasaurolophus would by slightly different in length.  A 1%
difference in a 3 metre crest would give a difference in resonant frequency
of about 0.6 Hz.  According to a physics book I have ("Modern Physics" by
Williams, Trinklein, and Metcalfe) this should produce beats.  "The number
of beats per second equals the difference between the frequencies of the
component waves."  If my reasoning is correct, the call of parasaurolophus
should have been a long throbbing note which was alternately loud and soft
every 0.6 seconds.

Does anyone have any comments on this idea?

Thanks,
Della Drury



  Blasts From the Past :  A study by Della Drury       

I started this study with the intention of calculating the resonant
frequencies of the airways of many different kinds of dinosaurs.  I reasoned
that the airway of an animal can be viewed as an open air column.

I started by going on the internet to find information about dinosaurs. I
came across a huge address list of museums in the U.S.A with fossil
exhibits.  I knew that not all of them would have dinosaurs and the
information that I was looking for about the skulls.  A lot of the museums
wrote back and a few emailed me.  Dr. Marc S. Frank of the Florida Museum of
Paleontology told me of a paleontological bulletin board on the internet:
vrtpaleo  So I decided to post my questions.  The responses I got helped
move my project along quite quickly.  Dr. Jeff Martz of Colorado State

[ Jeff would be flattered, but he's an undergraduate.  I think he's in
  his junior year now.  -- MR ]

University told me of yet another bulletin board: Dinosaur.  Vrtpaleo is for
paleontologists in general.  Dinosaur is for paleontologists who specialize
in dinosaurs.  I was surprised to find the number of busy and important
people who were willing to take the time to write to a Grade 9 kid.

I started with the idea that there would be easily available books filled
with the exact kind of measurements I needed.  At the beginning, I was
puzzled because my requests for this information did not produce results.  I
first began to understand this problem when I wrote to Dr.  William Simpson
of the Field Museum of Natural History in Chicago.  Since Dr. Simpson had
already been helpful in providing addresses for other paleotologists, I was
fairly sure that he would be able and willing to help again.  I asked for
measurements of the airways of hadrosaurs in the collection at the Field
Museum.  He answered:" I'd like to, but I do not have the time to fill such
requests." (Email: Nov. 22, 1996)  Dr. Cathy Forster of the State University
of New York was the first to explain my problem to me: "There are quite a
few hadrosaur specimens- but few of them are complete enough, and
undistorted enough, to provide good data. Measurements are not routinely
made.  First, the shape of the outside of the crest is not usually the shape
of the nasal passage.  And the exact shape of the nasal passage has been
difficult to get at.  Since it's inside, you need to destroy the outer bone
to reveal the inner passages.  However, Jack Horner has been CT scanning
hadrosaur crests lately, and has been able to track the nasal passages in
three dimensions.  Unfortunately, this work isn't published yet.  Also-
there really aren't very many dinosaur paleontologists, and there is so much
work left to do on dinosaurs.  No one has gotten around to seriously
studying nasal passages in hadrosaurs yet." (Email: Nov. 24, 1996)

Dr. Forster sent me 15 of her scale drawings of hadrosaur skulls.  She
traced the airways in red pen.

Dr. Michael Brett-Surman of the Smithsonian Institution suggested a
reference, Lull and Wright, a book containing a number of scale drawings of
hadrosaur skulls.  (Email: Oct. 25)  By using Dr. Forster's drawings as a
guide, I traced the airway passages of the diagrams in this book and
measured the lengths.  With each of these drawings and with Dr. Forster's
drawings I laid a string over the airway and measured the length of the
string to find the length of the airway.  This gave me what I needed to
calculate the resonant frequencies.  
Fundamental Frequencies of Nasal Cavities  (juv. = juvenile)
Lambeosaurus lambei     146 Hz  Lambeosaurus clavinitalis       212 Hz
Lambeosaurus lambei     105 Hz  Lambeosaurus magnicristatus     474 Hz (juv.)
Lambeosaurus lambei     146 Hz  Lambeosaurus magnicristatus     123 Hz
Lambeosaurus lambei     459 Hz (juv.)   Corythosaurus casuarius 109 Hz
Lambeosaurus lambei     122 Hz  Corythosaurus casuarius 141 Hz
Lambeosaurus clavinitalis       138 Hz  Corythosaurus casuarius 127 Hz
Lambeosaurus clavinitalis       161 Hz  Corythosaurus bicristatus       113 Hz
Corythosaurus intermedius       135 Hz  Corythosaurus brevicristatus    236 Hz
Corythosaurus intermedius       129 Hz  Procheneosaurus proceps 490 Hz (juv.)
Corythosaurus intermedius       145 Hz  Tetragonosaurus cranibrevis     268 Hz 
(juv.)
Corythosaurus intermedius       118 Hz  Parasaurolophus walkeri 52.8 Hz
                Parasaurolophus walkeri 60.1 Hz
I developed a two part hypothesis to guide my study:
1)  Some hadrosaurs used their crests as resonance chambers to produce low
frequency vocalizations.
2)      Predators could not hear the lowest of these frequencies.

Early in my study, I learned that Dr. David Weishampel had done a great deal
of work on the first part of my hypothesis. (Weishampel)  I know of no one
who has previously thought of the second part of my hypothesis.

As part of my project, I have built a model of a hadrosaurian nasal cavity
from PVC pipe and rubber hose.  The dinosaur that I decided to model is
Parasaurolophus walkeri. I chose this dinosaur because the lowest frequency
vocalizations were probably made by parasaurolophus. "The best
Parasaurolophus skull is at the Royal Ontario Museum in Toronto."  (Email:
J.D. Stewart, Curator of vertebrate paleontology at the Natural History
Museum of Los Angeles County: Oct. 8, 1996)   A specimen of apparently equal
quality was found in August, 1995 by Dr. Robert Sullivan and Dr. Tom
Williamson in New Mexico. (Williamson)  I have not been able to obtain the
exact dimensions of this latest specimen so I have built my model to the
dimensions of the specimen at the Royal Ontario Museum.

The speed of sound in air at 20OC is 343m/s (Hansson pg. 25)  The PVC pipe
part of the model represents the nasal cavity and has a length of 3.00 m.  I
have used v to stand for the speed of sound and l for the length of the air
column.  The calculated frequencies for the plastic pipe are:

f1 = fundamental frequency      = (1/2)v/ l     = 343/2x3       = 57.2 Hz
f2 = first harmonic     = (2/2)v/ l     = 2f1   = 114 Hz
f3 = second harmonic    = (3/2)v/ l     = 3f1   = 171 Hz
f4 = third harmonic     = (4/2)v/ l     = 4f1   = 229 Hz
f5 = fourth harmonic    = (5/2)v/ l     = 5f1   = 286 Hz

On December 21, Mr. Doug MacDonald of Peace River Electronics helped me make
measurements using his oscilloscope and a frequency generator which he built
especially for my project.  My model resonated at many more frequencies than
I expected.  

After some thought, I realized that my model was actually three resonance
columns in one: the plastic pipe, the rubber hose, and both the plastic pipe
and rubber hose together.  I did calculations to predict what frequencies
would resonate with the rubber hose and with the combination of the rubber
hose and plastic pipe together.  
For the rubber hose which has a length of 0.430m:
f1 = fundamental frequency      = (1/2)v/ l     = 343/(2x0.430)         = 73.7 
Hz
f2 = first harmonic     = (2/2)v/ l     = 2f1   = 147 Hz
f3 = second harmonic    = (3/2)v/ l     = 3f1   = 221 Hz
f4 = third harmonic     = (4/2)v/ l     = 4f1   = 295 Hz

For the plastic pipe and rubber hose combined which has a length of 3.43m:
f1 = fundamental frequency      = (1/2)v/ l     = 343/2x3.43    = 50.0 Hz
f2 = first harmonic     = (2/2)v/ l     = 2f1   = 100 Hz
f3 = second harmonic    = (3/2)v/ l     = 3f1   = 150 Hz
f4 = third harmonic     = (4/2)v/ l     = 4f1   = 200 Hz
f5 = fourth harmonic    = (5/2)v/ l     = 5f1   = 250 Hz
f6 = fifth harmonic     = (6/2)v/ l     = 6f1   = 300 Hz

The rubber hose on my model may be thought of as the distance down the
throat to the vocal apparatus. I assume that there was a vocal apparatus in
the dinosaur's throat.  

I expected two sources of error for the measured frequencies compared to the
calculated frequencies:     
1. The end of the resonating air column does not coincide exactly with the
end of the pipe.(Sears and Zemonsky, p. 503)     
2. The connection of the plastic pipe to the rubber hose is tapered.  This
means that the sound echoes from this location will be "fuzzy".

Calculated Frequency(Hz)        Measured Frequency(Hz    Percent Error(%)
        50.0    50      0
        57.2    57      -0.3
        73.7    71      -4.7              
        100     100     0
        114     115     0.8
        147     143     -2.7
        150     154     2.7
        171     167     -2.3
        200     200     0
        221     217     -1.8
        229     ?       ?
        250     250     0

The second part of my hypothesis has turned out to be difficult to test.  My
first idea was that the length of the cochlear duct in the middle ear of
predators would be the only factor determining the lowest frequency they
could hear.  The actual situation is more complicated.  The hairs inside the
cochlear duct send messages to the auditory nerve.  The stiffest hairs are
located near the beginning of the duct and are used to detect high
frequencies.  The soft hairs located deeper within the duct are used to
detect low frequencies. (Ritter et al.)  Of course, no one has ever seen
these structures in a dinosaur because they have not been fossilized.  I
assume that the soft tissues of dinosaur ears were much like those of living
birds and reptiles.

"On the whole reptiles (and even birds) have much poorer hearing than most
people realize.  The best guess is that they can use auditory information in
a narrow sense, as if they have a tuned receiver that responds appropriately
for signals within a narrow range of profiles.  The cochlear duct (ear
canal) can act as a tuned resonator to amplify some signals and in that
sense can indicate which frequencies are amplified, hence are important for
an animal." (Email: Dec. 3, 1996: Dr. Harry J. Jerison, U.C.L.A.)  The
cochlear duct is a delicate bony structure which is usually crushed and
distorted during fossilization.  However, its length can be determined by
the void in the larger bones which once contained it.  The cochlear duct is
a closed fluid column.  Once its length is known, its resonant frequencies
can be found as follows:

f1 = fundamental frequency      = (1/4)v/ l
f2 = first harmonic     = (3/4)v/ l
f3 = second harmonic    = (5/4)v/ l
f4 = third harmonic     = (7/4)v/ l

Here v represents the speed of sound but this time it is the speed of sound
in cochlear fluid rather than in air.  I assume that the cochlear fluid is
similar to sea water.  The speed of sound in sea water is 1510 m/s.
(Hansson, p. 25)  The l stands for the length of the fluid column.

At this point, my project ran into a wall.  I was not able to find the
length of a single cochlear duct.  " The ear region of dinosaurs is
generally poorly understood." (Email: Dec. 2, 1996: Dr. Phillip Currie,
Tyrrell Museum)  "I checked the library for articles on dinosaur hearing and
was surprised that a major biblio on dinosaurs had nothing on hearing, yet
had 4 citations on dinosaur urine! You were asking about cochlear length. I
talked to some people here and we all agree the cochlear (if dinosaurs had
one) would be soft tissue and thus not preserved. I'm aware of two articles
which discuss dinosaur stapes (an ear bone), one in the small theropod
DROMAEOSAURUS and in the hadrosaur CORYTHOSAURUS." (Email: Nov. 30, 1996:
Dr. Darren Tanke, Tyrrell Museum)

Dr. David Weishampel was able to find the lengths of cochlear ducts in
hadrosaurs (Weishampel, p. 257) and this what caused me to believe that I
would be able to do the same for theropods and crocodilians.  I now suspect
that my problem can be explained by the fact that there are always fewer
carnivores than herbivores.  There are fewer fossils of carnivores for me to
get my data.  "Truth is, dinosaur skeletons are pretty scarce, period."
(Horner and Lessem, p. 28)

Because hearing occurs by means of closed air columns, the predators had an
advantage in evolving to hear low frequencies.  Resonance in a closed air
column occurs at 1/4 of the wavelength.  In an open air column, the column
must be 1/2 the wavelength.  This means that the predators did not have to
evolve as fast as the herbivores to keep up in the frequency contest.
However, because sound travels about four times faster in cochlear fluid
than in air, the hadrosaurs would still have the advantage if the predators
had not evolved in other ways. " Troodon appears to have had a long cochlear
duct, but more of the large theropods appear to have had very shallow ones.
The theropods tended to extend the middle ear air chambers by diverticula
that enter all the bones around the braincase.  This greatly extended the
air volume behind the ear drum. This would have allowed them to extend their
range of hearing into the lower frequencies.  Presumably this would allow
them to pick up on deep bellowing sounds produced by herbivores." (Email:
Dec. 2, 1996: Dr. Phillip Currie, Tyrrell Museum)

The diverticula of the middle ear, would have acted as closed air columns to
amplify specific frequencies.  Since the middle ear was filled with air, the
advantage in the 'frequency contest' was with the predators.  They had less
adapting to do than did the hadrosaurs. "My guess is that any novel sounds
that hadrosaurs produced would force theropods to adapt in some manner to
take advantage of those frequencies. Certainly that seemed to be happening
with both troodontids and tyrannosaurs." (Email: Dec. 2, 1996: Dr. Phillip
Currie, Tyrrell Museum)  "Re your speculation, in predator-prey balances
such an imbalance would tend to be corrected by natural selection." (Email:
Dec. 3, 1996: Dr. Harry J. Jerison, U.C.L.A.)

Like my plastic model, each diverticulum acted together with the main
chamber of the middle ear to behave as though it were really three air
columns.  These were the diverticulum alone, the main air chamber, and the
diverticulum and main chamber together.  To complicate things further, a
sound wave emerging from a diverticulum could continue on to enter another
or several other diverticula.  There would be a whole series of "fourth" air
columns.

The outer ear canal would also have acted as an air column.  It would have
acted as both a closed air column and as an open air column.  This would
have occurred as a result of the flexibility of the ear drum.  Waves
striking the drum would reflect (closed air column) and transmit (open air
column) to interact with the air chamber of the middle ear and with its
diverticula.  This would add another layer of resonant frequencies.  Over
the X-mas holiday I had a chance to discuss this idea with Dr. David
Routledge of the University of Alberta.  By comparison with electrical
systems, Dr. Routledge believes that the flexibility of the ear drum would
have caused this air column to resonate at a frequency intermediate between
an open air column and a closed air column.  I hope to build a model to test
this idea.

Not everyone agrees with the first part of my hypothesis.  "I think you are
grasping at straws. This whole discussion presupposes that Weishampel's
vocalization hypothesis is fact. My opinion is that vocalizations are at
best hypothetical and that the crest of hadrosaurian dinosaurs probably
served  many functions, including olfaction, and in Parasaurolophus,
thermoregulation." (Email: Dec. 2, 1996: Dr. Robert Sullivan, State Museum
of Pennsylvania)

Most of what I've read says that the Weishampel hypothesis is one of the
best guesses.  "We are working on recreating the sounds using computers.
However, you are correct, that you can calculate the resonant frequencies
based on the dimensions of the airway passages." (Email: Oct. 24,1996: Dr.
Tom Williamson, New Mexico Museum of Natural History and Science)

 From the email messages I got from Dr. Currie and Dr. Jerison, it seems that
the second part of my hypothesis needs more thought.  For my work from this
point on, I'm going to use a new hypothesis:
2)      The frequencies to which predators' ears were tuned can be compared to
frequencies produces by hadrosaurs to determine which species of hadrosaur
were eaten by which predators.

I agree with Dr. Sullivan that the Weishampel hypothesis is unproven, but it
is not disproven and it continues to give me a frame of reference for my
work.  According to my science teachers, that is what an hypothesis in
supposed to do!



Bibliography

Sears and Zemansky 1963. University Physics

Lull and Wright  August 31,1942.Geological Sociey of American Special
Papers.  Hadrosaurian Dinosaurs of North America No.40; Published by the Society

Hansson, C.B. 1972. Physical Data Book; Pergammon

Horner and Lessem 1993. The Complete T-Rex

Ritter, Coombs, Drysdale, Gardner, and Lunn 1993. Biology. Toronto; Nelson
Canada

Weishampel 1981. "Acoustic Analysis of Potential Vocalization in
Lambeosaurine Dinosaurs (Reptilia: Ornithschia)" p. 252-261 Paleobiology 7(2)

Williamson (http://www.unm.edu/%7Egreywolf/test/nmfp963a.html). Did
Duck-billed Dinosaurs Quack?