48
Henry C. Bennet-Clark
Table 3. ComQarison of Qrimill}' and second!!!}' resonators involved in sound Qroduction
Insect
Mole cricket
Typical cicada
Bladder cicada
Scapteriscus
Cyclochila
Cystosoma
acletus (Fig.3)
australasiae
saundersii
Song frequency
2.7 kHz
4.3 kHz
830Hz
Primary resonator
Paired harps on
Paired tymbals
Paired tymbals
(see Sect. 3.3)
fore wings
on abdomen
on abdomen
Size of 1 ary resonator
5 x 3 mm
6x 5mm
4x3mm
Secondary resonator
Hom-shaped
Helmholtz
Thin-walled
burrow
resonator
bladder
Inertial element
Effective mass of
Effective mass of
Mass of flat areas
horn in burrow
tympanal openings Abdominal cuticle
Compliant element
Volume of
Volume of
Volume of
bulb in burrow
abdominal air sac
abdominal air sac
Acoustic output from
Mouth of
Large area of
Flat region of thin
secondary resonator
horn
thin tympana
wall of abdomen
Dimensions of 2ary
30 x 40 mm
IO x 22 mm
Two I 0 mrn diam
sound source(s)
+ one I 5 x I 0 mm
Song wavelength
I26mm
79mm
4IOmm
0Qtimal source diameter 40mm
25mm
130mm
For references, see text
In typical cicadas such as males of Cyclochila australasiae, the large
abdominal air sac and the thin tympana (or eardrums) act as the elements of a
Helmholtz resonator (Bennet-Clark and Young 1992). Although the tymbals are
the primary sound sources (Pringle 1954), the sound they emit is 13 dB quieter
than that emitted through the tympana which act as the effective sound source
(Young 1990). The efficiency of transduction of muscle power into sound power
may be as high as 46 % (Bennet-Clark and Daws 1999).
In male bladder cicadas such as Cystosoma saundersii, the elements of the
secondary resonator are the compliance of the large abdominal air sac and the
mass of the flat areas of abdominal cuticle from which the sound is radiated (Table
3). The abdominal bladder resonates sharply at the 830 Hz frequency of the
insects' song (Bennet-Clark and Young 1998).
All these secondary resonators share two features: first, the secondary
resonator considerably increases the source size and hence provides a closer match
between the source and the surrounding medium (Fig. I C); second, the sound is
radiated from the mass-like or inertial elements of the resonator.
Henry C. Bennet-Clark
Table 3. ComQarison of Qrimill}' and second!!!}' resonators involved in sound Qroduction
Insect
Mole cricket
Typical cicada
Bladder cicada
Scapteriscus
Cyclochila
Cystosoma
acletus (Fig.3)
australasiae
saundersii
Song frequency
2.7 kHz
4.3 kHz
830Hz
Primary resonator
Paired harps on
Paired tymbals
Paired tymbals
(see Sect. 3.3)
fore wings
on abdomen
on abdomen
Size of 1 ary resonator
5 x 3 mm
6x 5mm
4x3mm
Secondary resonator
Hom-shaped
Helmholtz
Thin-walled
burrow
resonator
bladder
Inertial element
Effective mass of
Effective mass of
Mass of flat areas
horn in burrow
tympanal openings Abdominal cuticle
Compliant element
Volume of
Volume of
Volume of
bulb in burrow
abdominal air sac
abdominal air sac
Acoustic output from
Mouth of
Large area of
Flat region of thin
secondary resonator
horn
thin tympana
wall of abdomen
Dimensions of 2ary
30 x 40 mm
IO x 22 mm
Two I 0 mrn diam
sound source(s)
+ one I 5 x I 0 mm
Song wavelength
I26mm
79mm
4IOmm
0Qtimal source diameter 40mm
25mm
130mm
For references, see text
In typical cicadas such as males of Cyclochila australasiae, the large
abdominal air sac and the thin tympana (or eardrums) act as the elements of a
Helmholtz resonator (Bennet-Clark and Young 1992). Although the tymbals are
the primary sound sources (Pringle 1954), the sound they emit is 13 dB quieter
than that emitted through the tympana which act as the effective sound source
(Young 1990). The efficiency of transduction of muscle power into sound power
may be as high as 46 % (Bennet-Clark and Daws 1999).
In male bladder cicadas such as Cystosoma saundersii, the elements of the
secondary resonator are the compliance of the large abdominal air sac and the
mass of the flat areas of abdominal cuticle from which the sound is radiated (Table
3). The abdominal bladder resonates sharply at the 830 Hz frequency of the
insects' song (Bennet-Clark and Young 1998).
All these secondary resonators share two features: first, the secondary
resonator considerably increases the source size and hence provides a closer match
between the source and the surrounding medium (Fig. I C); second, the sound is
radiated from the mass-like or inertial elements of the resonator.