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J.L. Aroyan et al.
constant frequency sound production over changing depths, allowing
the whale improved efficiency in monotonic sound production. Previous
studies have provided anatomical information and speculation on how
baleen whales may produce sound (Hosokawa 1950; Yablokov et al. 1972;
Sukhovskaya and Yablokov 1979; Purves and Pilleri 1983; Quayle 1991;
Reidenberg and Laitman 1992,1993; Haldiman and Tarpley 1993). Our goal
is to integrate the physics of sound production with blue whale laryngeal
anatomy to develop a verifiable model of how the blue whale produces
sound.
Before applying physical constraints to sound production in blue whales,
it is helpful to understand the variability within the blue whale call repertoire. Calls from the blue whales observed off the California shore have
been the most studies, and can be divided into four fundamental types,
shown in Figure 10. 14: (A) typically the first call of a series, consisting of
about 20 pulses spaced about 0.8 s apart, with each pulse subdivided into
multiple, time-offset nonharmonic components; (B) a harmonic sound typically 19 s in duration, sweeping or stepping down slightly in frequency from
about 20Hz to 16Hz; (C) a 9- to 12-Hz upswept tone preceding a type B
call; (D) an 80- to 30-Hz downsweep typically 2 to 5 s in duration, often produced by multiple animals as counter-calls and not produced in combination with the other call types. It is only the type B calls that provide a unique
constraint on the sound production model. Only the type B call is of continuous long duration such that the sound production mechanism is unlikely
to be able to recirculate the air used in producing the call. The calls shown
in Figure 1O.14a were recorded in the Santa Barbara Channel using
sonobuoy arrays for localizing the sound source in combination with visual
localization, leaving little doubt that blue whales were the source of these
sounds. Similar calls have been recorded from blue whales off California,
Oregon, and Baja California, Mexico (Thompson et al. 1992; D'Spain et al.
1995; McDonald et al. 1995; Stafford 1995; Rivers 1997). Type B calls have
reported source levels up to 190dB re 11lPa in recordings made off San
Nicolas Island, California (Aburto et al. 1997). The duration of the type B
calls illustrated in Figure 10.14 ranges from 16 to 21 s. The type A and B
blue whale calls often occur in patterns with regular pauses between calls
and longer pauses during breathing periods (Cummings and Thompson
1971; McDonald et al. 1995; Stafford 1995).
Blue whales have geographic call character variation, the animals off the
west coast of North America having similar call character for more than
thirty years (Thompson 1965) while blue whale calls from other regions are
distinctly different (Weston and Black 1965; Kibblewhite et al. 1967; Cummings and Thompson 1971; Northrup et aI.1971;Thompson and Friedl 1982;
Alling and Payne 1988; Alling et al. 1991) suggesting learned call character
within geographic variations as occurs in birdsong (Kroodsma 1996). The
type B call off the west coast of North America provides the longest continuous sound from blue whales known to the authors.
J.L. Aroyan et al.
constant frequency sound production over changing depths, allowing
the whale improved efficiency in monotonic sound production. Previous
studies have provided anatomical information and speculation on how
baleen whales may produce sound (Hosokawa 1950; Yablokov et al. 1972;
Sukhovskaya and Yablokov 1979; Purves and Pilleri 1983; Quayle 1991;
Reidenberg and Laitman 1992,1993; Haldiman and Tarpley 1993). Our goal
is to integrate the physics of sound production with blue whale laryngeal
anatomy to develop a verifiable model of how the blue whale produces
sound.
Before applying physical constraints to sound production in blue whales,
it is helpful to understand the variability within the blue whale call repertoire. Calls from the blue whales observed off the California shore have
been the most studies, and can be divided into four fundamental types,
shown in Figure 10. 14: (A) typically the first call of a series, consisting of
about 20 pulses spaced about 0.8 s apart, with each pulse subdivided into
multiple, time-offset nonharmonic components; (B) a harmonic sound typically 19 s in duration, sweeping or stepping down slightly in frequency from
about 20Hz to 16Hz; (C) a 9- to 12-Hz upswept tone preceding a type B
call; (D) an 80- to 30-Hz downsweep typically 2 to 5 s in duration, often produced by multiple animals as counter-calls and not produced in combination with the other call types. It is only the type B calls that provide a unique
constraint on the sound production model. Only the type B call is of continuous long duration such that the sound production mechanism is unlikely
to be able to recirculate the air used in producing the call. The calls shown
in Figure 1O.14a were recorded in the Santa Barbara Channel using
sonobuoy arrays for localizing the sound source in combination with visual
localization, leaving little doubt that blue whales were the source of these
sounds. Similar calls have been recorded from blue whales off California,
Oregon, and Baja California, Mexico (Thompson et al. 1992; D'Spain et al.
1995; McDonald et al. 1995; Stafford 1995; Rivers 1997). Type B calls have
reported source levels up to 190dB re 11lPa in recordings made off San
Nicolas Island, California (Aburto et al. 1997). The duration of the type B
calls illustrated in Figure 10.14 ranges from 16 to 21 s. The type A and B
blue whale calls often occur in patterns with regular pauses between calls
and longer pauses during breathing periods (Cummings and Thompson
1971; McDonald et al. 1995; Stafford 1995).
Blue whales have geographic call character variation, the animals off the
west coast of North America having similar call character for more than
thirty years (Thompson 1965) while blue whale calls from other regions are
distinctly different (Weston and Black 1965; Kibblewhite et al. 1967; Cummings and Thompson 1971; Northrup et aI.1971;Thompson and Friedl 1982;
Alling and Payne 1988; Alling et al. 1991) suggesting learned call character
within geographic variations as occurs in birdsong (Kroodsma 1996). The
type B call off the west coast of North America provides the longest continuous sound from blue whales known to the authors.