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T.W. Cranford
waveforms [shown in their figure 5] place the click generator at the location of the nasal plugs in the nares, a site also implicated by anatomic evidence." Their work was significant because the triangulation technique
supported nasal phonation and circumscribed a particular region within the
forehead as the source of sound. Since their calculations and conclusions
were based upon simplified, straight-line propagation, some error should be
expected in their choice of a source location. We now know that many of
the fatty forehead tissues have different propagation velocities and are
capable of bending or refracting sound and producing complex interference
patterns. Their anatomic choice of the "nasal plug" area was apparently
based upon the earlier suggestion of Evans and Prescott (1962) and not
upon precise triangulation.
In addition, Norris and his colleagues (1971) made cineradiographic
observations of dolphins during phonation. They monitored air moving dorsally from the bony nares into the upper nasal passages during phonation,
demonstrating that the mechanism is driven pneumatically. By timing
emitted sounds and correlating them to events on the X-ray movie films
they could say with some assurance that the sounds were produced in the
nasal apparatus (forehead). They also found an absence of movement in
the larynx during phonation, and so implicated structures in the forehead
without specifying the exact site. Similar techniques and observations
arrived later with similar conclusions (Dormer 1974, 1979; Hollien et al.
1976).
Although the cineradiographic evidence gathered by Norris, Dormer, and
their colleagues provided an almost irrefutable case for nasal phonation in
the early 1970s, it was apparently not widely understood. It was only after
work in the early 1980s that the question of laryngeal versus nasal phonation was unequivocally settled. Before we review that work, it may be
instructive to highlight the important role played by one of the world's most
bizarre beasts in the discovery of the sound generation complex and its
mechanism.
2.2 The Unique Example of the Sperm Whale
Biologists generally recognize that sperm whales (Physeteridae) are a study
in extremes, making them strong candidates for producing illuminating
comparisons. During the early 1970s, interest in the unique nasal anatomy
of the sperm whale (Physeter catodon) provided an intriguing "twist" on
the investigations into odontocete sound generation.
When compared to other odontocetes, the physeterid nasal apparatus
contains a major (180°) twist and forward expansion in the arrangement of
homologous structures (Cranford et al. 1996; Cranford 1999). This is particularly evident from the peculiar outgrowth of the mesorostral cartilage
that occurs during ontogeny (Klima et al. 1986; Klima 1999). In addition, a
part of the nasal complex in the sperm whale is greatly hypertrophied,
T.W. Cranford
waveforms [shown in their figure 5] place the click generator at the location of the nasal plugs in the nares, a site also implicated by anatomic evidence." Their work was significant because the triangulation technique
supported nasal phonation and circumscribed a particular region within the
forehead as the source of sound. Since their calculations and conclusions
were based upon simplified, straight-line propagation, some error should be
expected in their choice of a source location. We now know that many of
the fatty forehead tissues have different propagation velocities and are
capable of bending or refracting sound and producing complex interference
patterns. Their anatomic choice of the "nasal plug" area was apparently
based upon the earlier suggestion of Evans and Prescott (1962) and not
upon precise triangulation.
In addition, Norris and his colleagues (1971) made cineradiographic
observations of dolphins during phonation. They monitored air moving dorsally from the bony nares into the upper nasal passages during phonation,
demonstrating that the mechanism is driven pneumatically. By timing
emitted sounds and correlating them to events on the X-ray movie films
they could say with some assurance that the sounds were produced in the
nasal apparatus (forehead). They also found an absence of movement in
the larynx during phonation, and so implicated structures in the forehead
without specifying the exact site. Similar techniques and observations
arrived later with similar conclusions (Dormer 1974, 1979; Hollien et al.
1976).
Although the cineradiographic evidence gathered by Norris, Dormer, and
their colleagues provided an almost irrefutable case for nasal phonation in
the early 1970s, it was apparently not widely understood. It was only after
work in the early 1980s that the question of laryngeal versus nasal phonation was unequivocally settled. Before we review that work, it may be
instructive to highlight the important role played by one of the world's most
bizarre beasts in the discovery of the sound generation complex and its
mechanism.
2.2 The Unique Example of the Sperm Whale
Biologists generally recognize that sperm whales (Physeteridae) are a study
in extremes, making them strong candidates for producing illuminating
comparisons. During the early 1970s, interest in the unique nasal anatomy
of the sperm whale (Physeter catodon) provided an intriguing "twist" on
the investigations into odontocete sound generation.
When compared to other odontocetes, the physeterid nasal apparatus
contains a major (180°) twist and forward expansion in the arrangement of
homologous structures (Cranford et al. 1996; Cranford 1999). This is particularly evident from the peculiar outgrowth of the mesorostral cartilage
that occurs during ontogeny (Klima et al. 1986; Klima 1999). In addition, a
part of the nasal complex in the sperm whale is greatly hypertrophied,