Unpublished doctoral dissertation,
University of Hawaii
Humpback whale bioacoustics: From form to function
- Eduardo Mercado III
- University of Hawaii, Kewalo Basin Marine Mammal Lboratory,
1129 Ala Moana Blvd., Honolulu, HI, USA, 96814
-
- (C) 1998 University of Hawaii
This thesis investigates how humpback whales produce, perceive,
and use sounds from a comparative and computational perspective.
Biomimetic models are developed within a systems-theoretic framework
and then used to analyze the properties of humpback whale sounds.
First, sound transmission is considered in terms of possible production
mechanisms and the propagation characteristics of shallow water
environments frequented by humpback whales. A standard source-filter
model (used to describe human sound production) is shown to be
well suited for characterizing sound production by humpback whales.
Simulations of sound propagation based on normal mode theory reveal
that optimal frequencies for long range propagation are higher
than the frequencies used most often by humpbacks, and that sounds
may contain spectral information indicating how far they have
propagated. Next, sound reception is discussed. A model of human
auditory processing is modified to emulated humpback whale auditory
processing as suggested by cochlear anatomical dimensions. This
auditory model is used to generate visual representations of humpback
whale sounds that more clearly reveal what features are likely
to be salient to listening whales. Additionally, the possibility
that an unusual sensory organ (the tubercle) plays a role in acoustic
processing is assessed. Spatial distributions of tubercles are
described that suggest tubercles may be useful for localizing
sound sources. Finally, these models are integrated with self-organizing
feature maps to create a biomimetic sound classification system,
and a detailed analysis of individual sounds and sound patterns
in humpback whale “songs” is performed. This analysis
provides evidence that song sounds and sound patterns vary substantially
in terms of detectability and propagation potential, suggesting
that they do not all serve the same function. New quantitative
techniques are also presented that allow for more objective characterizations
of the long term acoustic features of songs.
The quantitative framework developed in this thesis provides a
basis for theoretical consideration of how humpback whales (and
other cetaceans) might use sound. Evidence is presented suggesting
that vocalizing humpbacks could use sounds not only to convey
information to other whales, but also to collect information about
other whales. In particular, it is suggested that sounds currently
believed to be primarily used as communicative signals, might
be primarily used as sonar signals. This theoretical framework
is shown to be generalizable to other baleen whales and to toothed
whales.
- Mercado, Eduardo III (1998). Humpback whale bioacoustics: From
form to function. Unpublished doctoral dissertation. University
of Hawaii.
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