10. Acoustic Models of Sound Production
461
geal sac lengths plotted as a percentage of the whale's length. Many of the
data points are unfortunately from embryos (Sukhovskaya and Yablokov
1979) or juveniles, which appear not to be representative of laryngeal development in adult animals. More anatomical data are needed to constrain the
volumetric equations presented previously, as well as to address questions
of variability between species.
9. Summary
We have presented a new model for sound production by blue whales.
Several lines of evidence suggest that the type "B" blue whale call is
best represented by monopole source oscillations of an air-filled cavity.
Volume displacement requirements based on sound frequency, duration,
and intensity suggest that most of the whale's lung capacity is required
to produce the loud, low-frequency type "B" calls. A system is proposed to
model blue whale sound production, in which air moves between the lungs
and the rigid nasal passages while the whale is diving or ascending in
the water column. An absolute depth limit for calling of any type occurs
when both the lungs and the laryngeal sac have totally collapsed at about
220m, while the time-averaged depth for producing the type "B" call is
required to be around 30m. The model also predicts that feeding behavior
is incompatible with the swim profile and may be incompatible with
the requirement that the nasal passages connect to the trachea, possibly
blocking the esophagus. The lack of depth-related changes in call characteristics and the anatomy suggest that resonance may be of the Helmholtz
type with a low to moderate quality factor (Q). Continued research is
expected to provide dive profile information from calling blue whales,
testing the proposed model.
Acknowledgments. James Aroyan wishes to thank Whit Au and Joel Kent
(Elo TouchSystems, Inc., Fremont, CA) for their insightful comments on his
dissertation, and Ted Cranford for providing the CT scan of a common
dolphin used in this investigation. The author also thanks Geoffrey Vallis
(Geophysical Fluid Dynamics Laboratory, Princeton University) and the
UC Santa Cruz Physics department for partial support during the final
phase of his doctoral project. James adds a dedication of this chapter to the
memory of his father, Harry 1. Aroyan (1921-1998).
Help with the mathematics in developing the blue whale sound production model was provided by Ron Kessel. Sue Moore and Kate Stafford
expanded our understanding of blue whales through many conversations
and their help at sea. John Heyning provided access to the L. A. county
museums collections.
461
geal sac lengths plotted as a percentage of the whale's length. Many of the
data points are unfortunately from embryos (Sukhovskaya and Yablokov
1979) or juveniles, which appear not to be representative of laryngeal development in adult animals. More anatomical data are needed to constrain the
volumetric equations presented previously, as well as to address questions
of variability between species.
9. Summary
We have presented a new model for sound production by blue whales.
Several lines of evidence suggest that the type "B" blue whale call is
best represented by monopole source oscillations of an air-filled cavity.
Volume displacement requirements based on sound frequency, duration,
and intensity suggest that most of the whale's lung capacity is required
to produce the loud, low-frequency type "B" calls. A system is proposed to
model blue whale sound production, in which air moves between the lungs
and the rigid nasal passages while the whale is diving or ascending in
the water column. An absolute depth limit for calling of any type occurs
when both the lungs and the laryngeal sac have totally collapsed at about
220m, while the time-averaged depth for producing the type "B" call is
required to be around 30m. The model also predicts that feeding behavior
is incompatible with the swim profile and may be incompatible with
the requirement that the nasal passages connect to the trachea, possibly
blocking the esophagus. The lack of depth-related changes in call characteristics and the anatomy suggest that resonance may be of the Helmholtz
type with a low to moderate quality factor (Q). Continued research is
expected to provide dive profile information from calling blue whales,
testing the proposed model.
Acknowledgments. James Aroyan wishes to thank Whit Au and Joel Kent
(Elo TouchSystems, Inc., Fremont, CA) for their insightful comments on his
dissertation, and Ted Cranford for providing the CT scan of a common
dolphin used in this investigation. The author also thanks Geoffrey Vallis
(Geophysical Fluid Dynamics Laboratory, Princeton University) and the
UC Santa Cruz Physics department for partial support during the final
phase of his doctoral project. James adds a dedication of this chapter to the
memory of his father, Harry 1. Aroyan (1921-1998).
Help with the mathematics in developing the blue whale sound production model was provided by Ron Kessel. Sue Moore and Kate Stafford
expanded our understanding of blue whales through many conversations
and their help at sea. John Heyning provided access to the L. A. county
museums collections.