@article {47882, title = {Bioacoustics of a miniature cricket, Cycloptiloides canariensis (Orthoptera: Gryllidae: Mogoplistinae)}, journal = {J Exp Biol}, volume = {198}, year = {1995}, month = {1995}, pages = {721-8}, abstract = {

Male crickets, Cycloptiloides canariensis (body length 5 mm), stridulate with their forewings, which are hidden during rest under the large shield-like pronotum. The wings are opened into the stridulatory position by bending the body between the pro- and mesothorax. The song is a 2 s trill composed on average of 260 pulses (syllables) with a carrier frequency of about 6 kHz. The sound-emitting structures on the wings have been studied by laser vibrometry and particle dusting. A distinct membrane area, which includes a prominent mirror cell, acts as a resonator, amplifying the fundamental carrier frequency produced by interactions between the file and plectrum. The resonating membrane is extremely thin (mirror cell thickness 0.2 \µm), which is a physical requirement for maintaining the carrier frequency in the cricket-specific range. Covering the wings after singing is probably an adaptation to protect these delicate structures from damage by mechanical contact during social interactions, especially mating.

}, issn = {1477-9145}, author = {M Dambach and A Gras} } @article {47868, title = {Ticking of the clockwork cricket: the role of the escapement mechanism.}, journal = {J Exp Biol}, volume = {205}, year = {2002}, month = {2002 Mar}, pages = {613-25}, abstract = {

The \&$\#$39;clockwork cricket\&$\#$39; model for cricket sound production suggests that the catch-and-release of the file of one forewing by the plectrum on the opposite wing act as an \&$\#$39;escapement\&$\#$39; to provide the phasic impulses that initiate and sustain the vibration of the resonant regions of the wings from which the sounds are produced. The action of the escapement produces the familiar ticking sound of clocks. The higher-frequency components of the songs of twelve species of cricket were analysed after removing the dominant low-frequency components and amplifying the remaining higher-frequency components. In normal song pulses of all species, the higher-frequency components showed a close phase-locking to the waveform of the dominant frequency, but the amplitude of the higher-frequency components did not correlate with that at the dominant frequency. Anomalous pulses occurred spontaneously in the songs of several species: multimodal, interrupted or curtailed pulses are described. In all of these, the anomalous pulse envelope was associated with changes in the amplitude and/or instantaneous frequency of the higher-frequency components of the sound. A model of the escapement suggests that the frequency of the residual components of the song depends on the symmetry of action of the plectrum on the teeth of the file.

}, keywords = {animal vocalization, animal wings, Animals, escape reaction, Gryllidae, species specificity}, issn = {0022-0949}, author = {H. C. Bennet-Clark and Winston J. Bailey} } @article {47861, title = {The control of carrier frequency in cricket calls: a refutation of the subalar-tegminal resonance/auditory feedback model.}, journal = {J Exp Biol}, volume = {203}, year = {2000}, month = {2000 Feb}, pages = {585-96}, abstract = {

The subalar-tegminal resonance/auditory feedback hypothesis attempts to explain how crickets control the carrier frequency (f(C)), the loudness and the spectral purity of their calls. This model contrasts with the \&$\#$39;clockwork cricket\&$\#$39; or escapement model by proposing that f(C) is not controlled by the resonance of the cricket\&$\#$39;s radiators (the harps) but is instead controlled neurally. It suggests that crickets are capable of driving their harps to vibrate at any frequency and that they use a tunable Helmholtz-like resonator consisting of the tegmina and the air within the subalar space to amplify and filter the f(C). This model predicts that f(C) is variable, that call loudness is related to tegminal position (and subalar volume) and that low-density gases should cause f(C) to increase. In Anurogryllus arboreus, f(C) is not constant and varied by as much as 0.8 \% between pulses. Within each sound pulse, the average f(C) typically decreased from the first to the last third of a sound pulse by 9 \%. When crickets called in a mixture of heliox and air, f(C) increased 1.07- to 1.14-fold above the value in air. However, if the subalar space were part of a Helmholtz-like resonator, then its resonant frequency should have increased by 40-50 \%. Moreover, similar increases occurred in species that lack a subalar space (oecanthines). Experimental reduction of the subalar volume of singing crickets resulted neither in a change in f(C) nor in a change in loudness. Nor did crickets attempt to restore the subalar volume to its original value. These results disprove the presence of a subalar-tegminal resonator. The free resonance of freshly excised Gryllus rubens tegmina shifted by 1.09-fold when moved between air and a mixture of helium and air. Auditory feedback cannot be the cause of this shift, which is similar to the f(C) shifts in intact individuals of other species. Calculations show that the harp is 3.9-1.8 times more massive than the air that moves en masse with the vibrating harps. Replacing air with heliox-air lowers the mass of the vibrating system sufficiently to account for the f(C) shifts. These results re-affirm the \&$\#$39;clockwork cricket\&$\#$39; (escapement) hypothesis. However, as realized by others, the harps should be viewed as narrow-band variable-frequency oscillators whose tuning may be controlled by factors that vary the effective mass.

}, keywords = {acoustic stimulation, animal vocalization, Animals, biological models, feedback, Gryllidae, male, vibration}, issn = {0022-0949}, author = {Prestwich, K N and Lenihan, K M and Martin, D M} } @article {20902, title = {Sexual signalling in bladder grasshoppers: tactical design for maximizing calling range.}, journal = {J Exp Biol}, volume = {200}, year = {1997}, month = {1997 Oct}, pages = {2597-608}, abstract = {

Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150m for the male signal in the afternoon increased to 1.5-1.9km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter- and intraspecific pressures and by the transmission channel.

}, keywords = {animal sexual behaviour, Animals, female, grasshoppers, male}, issn = {0022-0949}, author = {Moira J. van Staaden and Heiner R{\"o}mer} } @article {17210, title = {Tymbal mechanics and the control of song frequency in the cicada Cyclochila australasiae}, journal = {J Exp Biol}, volume = {200}, year = {1997}, month = {1997}, pages = {1681-94}, abstract = {

The anatomy of the tymbal of Cyclochila australasiae was re-described and the mass of the tymbal plate, ribs and resilin pad was measured. The four ribs of the tymbal buckle inwards in sequence from posterior to anterior. Sound pulses were produced by pulling the tymbal apodeme to cause the tymbal to buckle inwards. A train of four sound pulses, each corresponding to the inward buckling of one rib, could be produced by each inward pull of the apodeme, followed by a single pulse as the tymbal buckled outwards after the release of the apodeme. Each preparation produced a consistent sequence of pulses. Each of the pulses produced had its maximum amplitude during the first cycle of vibration. The waveform started with an initial inward-going rarefaction followed by a larger outward compression, followed by an approximately exponential decay, as is typical of a resonant system. The mean dominant frequencies of the pulses produced during the inward movement were 4.37, 4.19, 3.92 and 3.17 kHz respectively. The pulse produced during the outward movement had a mean resonant frequency of 6.54 kHz. This suggests that the mass-to-stiffness ratio that determines the resonant frequencies of the various pulses differs from pulse to pulse. If succeeding pulses followed rapidly, the next pulse tended to start on the inward-going half-cycle of its predecessor and to produce a coherent waveform. Coherence was lost if the preceding pulse had decayed to below approximately one-tenth of its peak amplitude. When the tymbal plate was loaded by a 380 \µg wire weight, the resonant frequency of all sound pulses was reduced. Pulses produced later in the inward buckling sequence were less affected by the loading than earlier ones. This suggests that the effective mass determining the resonance in the later pulses is greater than that in the earlier pulses. The frequency of the pulses produced in the outward movement was affected most, suggesting that the mass involved was less than that in any of the pulses produced by the inward movement. The quality factor, Q, of the pulses produced by the inward buckling of the unloaded tymbal was approximately 10. For the outward buckling, Q was approximately 6. The Q of loaded tymbals was higher than than that of unloaded tymbals. The Q of the resonances varied approximately as the reciprocal of the resonant frequency. Experimental removal of parts of the tymbal showed that the thick dorsal resilin pad was an important elastic determinant of the resonant frequency, but that the mass and elasticity of the tymbal ribs were also determinants of the resonant frequency. The major element of mass is the tymbal plate. The integrity of the tymbal ribs was essential if the buckling movement were to occur. The force required to cause inward buckling of the tymbal was approximately 0.25 N. The force required to hold the tymbal in the buckled-in position was approximately 0.05 N. This asymmetry in the tymbal compliance, together with the different masses involved in inward and outward buckling, may account for the difference between the resonant frequencies of the inward-going and outward-going clicks. The tymbal appears to act as an energy storage mechanism that releases energy as the tymbal ribs buckle inwards in sequence. Each pulse provides a large initial impulse to the abdominal resonator, followed by a sustaining resonant vibration at, or close to, the song frequency. Subsequent pulses maintain the coherent resonance of the song pulse.

}, issn = {1477-9145}, url = {http://jeb.biologists.org/content/200/11/1681.long}, author = {H. C. Bennet-Clark} } @article {17209, title = {Transduction of mechanical energy into sound energy in the cicada Cyclochila australasiae}, journal = {J Exp Biol}, volume = {202 (Pt 13)}, year = {1999}, month = {1999 Jul}, pages = {1803-17}, abstract = {

The anatomy of the paired tymbal muscles of Cyclochila australasiae was described. Force-distance relationships of the sound-producing in-out cycle of tymbal movement were measured. The largest forces were measured when the push occurred at the apodeme pit on the tymbal plate at angles similar to the angles of internal pull of the tymbal muscle. Initially, inward movement was opposed by the elasticity of the tymbal, which stored energy. At a mean force of 0. 38 N after a mean inward strain of 368 microm, the tymbal ribs buckled, the mean energy release being 45.1 microJ. The energy release occurred over 2-10 ms in three or four sound-producing steps as successive tymbal ribs buckled inwards. After the ribs had buckled, the force decreased to a mean value of 0.17 N. The force returned to zero during the outward movement, during which the tymbal ribs buckled outwards. The mean energy dissipated in the outward movement was 32.8 microJ. During contraction, the tymbal muscle produced mean values for the peak active force of 0.31 N over 295 microm, which gave mean values for the area of the work loops of 47.0 microJ. The calling song of C. australasiae had a mean pulse rate of 234 Hz (117 Hz for each side of the insect). The peak power to mean power ratio for the songs was 8.51:1 (+9.30 dB). Measurements of the sound field around tethered insects and of the peak power to mean power ratio of the songs gave values for the mean power of the song of 3.15-7 mW; these correspond to an energy per song pulse of 13.5-30 microJ. Previously reported mean values are 3. 15 mW for protest song and 5.1 mW for calling song. The efficiency of transduction of mechanical energy into sound energy is between 18 and 46 \%.

}, issn = {1477-9145}, url = {http://jeb.biologists.org/content/202/13/1803.long}, author = {H. C. Bennet-Clark and Daws, AG} } @article {17208, title = {The role of the tymbal in cicada sound production}, journal = {J Exp Biol}, volume = {198}, year = {1995}, month = {1995}, pages = {1001-20}, abstract = {

1. The tymbal of Cyclochila australasiae consists of a biconvex membrane bearing alternating long and short ribs anteriorly and an irregularly shaped tymbal plate posteriorly. These sclerotised regions are coupled together by the surrounding highly flexible cuticle, which contains resilin. Dorsally, there is a thick pad of resilin, which functions as a spring, returning the tymbal to the out position and maintaining the stress on the long ribs. 2. Contraction of the tymbal muscle causes the tymbal plate to swing inwards, acting as a lever so that the surface of the tymbal moves through more than twice the distance of muscle shortening. This produces an inward movement and twisting of the dorsal ends of the long ribs, which then buckle in sequence, with each rib undergoing a sudden deformation from a convex to a V-shaped profile. Buckling takes place at the rib\&$\#$39;s weakest point, which is the narrow, highly sclerotised mid-region. 3. Inward buckling of the tymbal generates a loud click with a dominant frequency around 4 kHz. Resonances close to 4 kHz can be demonstrated in a buckled-in tymbal when driven by internal sound or by vibration at the tymbal plate. These resonances occur in sealed cicadas and those in which the abdominal air sac has been opened at both its anterior and posterior ends, which shows that the resonances are not due to the air sac; the tymbal itself is a resonant system. The maximum amplitude of tymbal vibration occurs at the V-shaped dimples in the centre of the long ribs. 4. When the tymbal plus abdominal air sac system is driven by vibration at the tymbal plate, the Q3dB of the sound radiated through the tympana is about 12.5, which is approximately the sum of those of the tymbal (Q=9.3) and of the air sac (Q=3.4) resonators. When the tymbal is not loaded by the air sac, i.e. in the sealed cicada and open cicada preparations, the Q3dB of its resonance is higher, between 13 and 20. 5. The click produced as the tymbal pops out is over 20 dB quieter than the in-click and has a dominant frequency around 6 kHz. When driven in the resting position, resonances are found close to 6 kHz but there is only a weak general vibration of the ribs and tymbal plate. When the tymbal is pushed in gradually, the resonant frequency changes from about 5.5 kHz to about 4.3 kHz as the tymbal buckles inwards. The left and right tymbals of the same insect may differ slightly in their acoustic properties. 6. As the tymbal buckles inwards, it displaces a volume of approximately 6 \µl into the abdominal air sac volume of about 2 ml. The resulting sound pressure inside the air sac attains peak values of 155\­159 dB SPL; the root mean square values are 141\­144 dB SPL. The mean peak value just outside the tympana is 148.5 dB SPL. 7. Overall, the present work supports and extends our earlier model of cicada sound production: the tymbal click provides a coherent resonant source that drives the abdominal resonator, from which sound is radiated via the tympana. At the same time, the system provides the pressure transformation between muscle power and sound power that is desirable for efficient sound radiation.

}, issn = {1477-9145}, author = {Young, D and H. C. Bennet-Clark} } @article {17207, title = {Acoustics of a small Australian burrowing cricket: the control of low-frequency pure-tone songs.}, journal = {J Exp Biol}, volume = {204}, year = {2001}, month = {2001 Aug}, pages = {2827-41}, abstract = {

For most insects, size determines the call frequency. This paper describes the acoustics of a small brachypterous cricket (Rufocephalus sp.; body length 9.6 mm) producing a call with a carrier frequency of approximately 3.2 kHz from a subterranean burrow. Crickets such as Gryllus campestris are approximately twice this length and produce a call frequency close to 5 kHz. The burrow of Rufocephalus opens via a small hole with a diameter of 3.2 mm. The neck of the hole at approximately 1.4 mm depth opens to a vertical two-part burrow with an upper vase-shaped chamber 16.1 mm in height with a diameter of 9.4 mm. This top chamber connects via a 6.4mm high (diameter 5.2 mm) neck to a more irregular chamber approximately 18 mm high with a width of approximately 11 mm. The walls of the top chamber neck and of the upper part of the lower chamber are smooth and appear to be sealed with saliva. The song has a mean centre frequency of 3.2 kHz and is made up of variable-length trills of pulses of mean duration 15.8 ms. Many song pulses had smooth envelopes and their frequency did not vary by more than +/-40Hz from the centre frequency, with a relative bandwidth Q-3dB of over 50. Other pulses showed considerable amplitude and frequency modulation within the pulse. When driven by external sound, burrows resonated at a mean frequency of 3.5 kHz with a mean quality factor Q of 7.4. Natural-size model burrows resonated at similar frequencies with similar Q values. One cricket, which had previously called from its own burrow at 2.95 kHz, sang at 3.27 kHz from a burrow that resonated at the same frequency. Life-size model burrows driven by external sound resonated at similar frequencies to the actual burrows; models three times life size resonated at one-third of this frequency. In all models, the sound pressure was more-or-less constant throughout the top chamber but fell rapidly in the neck of the burrow; the phase of the sound was effectively constant in the top chamber and neck and fell through approximately 180 degrees in passing from the neck into the lower chamber. A numerical model of the sound flow from region to region gave essentially similar results. A resonant electrical model fed from a high-impedance source with discrete tone bursts at different frequencies showed similar amplitude and frequency modulation to the various types of song pulses that were observed. It is suggested that the high purity of the songs results from close entrainment of the sound-producing mechanism of the insect\&$\#$39;s wings to the sharply resonant burrow.

}, keywords = {acoustics, animal vocalization, Animals, Australia, environment, Gryllidae}, issn = {0022-0949}, url = {http://jeb.biologists.org/content/204/16/2827.long}, author = {Winston J. Bailey and H. C. Bennet-Clark and Fletcher, N H} } @article {17206, title = {Wing resonances in the Australian field cricket Teleogryllus oceanicus.}, journal = {J Exp Biol}, volume = {206}, year = {2003}, month = {2003 May}, pages = {1479-96}, abstract = {

The anatomy and mechanics of the fore-wings of the Australian cricket Teleogryllus oceanicus were examined to study how resonances of the wings were excited, to model the interactions between the two wings during sound production, to account for the frequency changes that occur within the pulses and to determine the variation in sound amplitude during the pulses. Sound is produced after raising the wings by closing the right wing over the left; the plectrum of the left wing engages and releases teeth on the file on the underside of the right wing. The mean number of teeth on the right file is 252; the teeth are more closely spaced in the posterior part of the file, which is engaged at the start of the song pulses. The anterior part of the file is separated from the base of the harp by a short flexible region. The dorsal field of the wing, in which the harp is situated, is largely mechanically isolated from the driving veins of the lateral field, except for a cross vein at the apex of the harp. The harps of the two wings did not differ significantly in area but the plectrum of the left wing was significantly longer and wider than that of the right wing. The posterior edge of the plectrum has a radius of approximately 0.5 micro m, which allows it to engage the 20 micro m-tall teeth of the file. The plectrum is separated from the wing by a 0.5 micro m-thick crescent that allows it to twist lengthways and thus disengage the file teeth. The sigmoid shape of the file allows the plectrum to engage teeth over most of the length of the file. The calling song of T. oceanicus consists of a chirp of four similar pulses followed by a trill of pairs of pulses. The dominant frequency of all pulses is approximately 4.8 kHz but cycle-by-cycle analysis suggests that the different types of pulse are produced by wing-closing movements through different arcs. Free resonances of the left wing occurred at 4.56 kHz [quality factor (Q)=25.1] and of the right wing at 4.21 kHz (Q=23.9). Driven by loud sound, maximum vibration of the harp was seen at approximately 4.5 kHz; at lower sound levels, the vibration was confined to the cross-veins of the harp that extend distally from the file. Resonances of the left wing driven by vibration of the same wing, either at the plectrum or on the anal area, occurred at similar frequencies to those of the songs and had similar Qs but were approximately anti-phase, demonstrating that movement of the plectrum (e.g. by the file teeth) causes an opposite movement of the harp. When the right wing was driven directly on the file, the resonant frequency was 5.88 kHz but, when driven on the file via a length of the left file and the left plectrum, it was 4.83 kHz. The amplitude of the vibration increased from the posterior end of the file to the middle then fell towards the anterior end of the file. Pushing a left plectrum across the middle of the right file produced trains of damped sound pulses at 4.82 kHz (Q=23.4). Clicks excited from the anterior end of the file had lower frequencies. The resonances excited from both the left wing via its plectrum and from the right wing when driven via the left plectrum were similar in frequency to that of the song. The resonance of the dorsal field persisted after ablation of the harp but the mean resonant frequency increased 1.12-fold with a similar Q to the intact wing. Droplets of water on the distal end of the harp or proximal part of the dorsal field raised the resonant frequency. The resonant frequency was lowered by the addition of weights to the harp or the file; the factor of the decrease suggested that the mass of the resonant system was approximately 1.4 mg, which accords with the mass of the harp plus file plus anal area of the wing (left wing, 1.27 mg; right wing, 1.15 mg) but is far heavier than the harp (0.22 mg). An earlier suggestion that the harp is the resonator is not supported; instead, it is proposed that the major elastic component of the resonant system is the file plus 1st anal vein and that the mass component is the combined mass of the file, anal area and harp.

}, keywords = {animal communication, animal wings, Animals, Gryllidae, sound spectrography}, issn = {0022-0949}, author = {H. C. Bennet-Clark} }