01910nas a2200181 4500008004100000245007300041210006900114520135500183653001001538653001101548653002901559653001101588653001301599100002001612700002101632700002001653856005501673 2014 eng d00aMechanical basis of otoacoustic emissions in tympanal hearing organs0 aMechanical basis of otoacoustic emissions in tympanal hearing or3 a

Tympanal hearing organs of insects emit dis- tortion–product otoacoustic emissions (DPOAes), which in mammals are used as indicator for nonlinear cochlear amplification, and which are highly vulnerable to manipu- lations interfering with the animal’s physiological state. Although in previous studies, evidence was provided for the involvement of auditory mechanoreceptors, the source of DPOAe generation and possible active mechanisms in tympanal organs remained unknown. Using laser Dop- pler vibrometry in the locust ear, we show that DPOAes mechanically emerge at the tympanum region where the auditory mechanoreceptors are attached. Those emission- coupled vibrations differed remarkably from tympanum waves evoked by external pure tones of the same frequency, in terms of wave propagation, energy distribution, and loca- tion of amplitude maxima. Selective inactivation of the auditory receptor cells by mechanical lesions did not affect the tympanum’s response to external pure tones, but abol- ished the emission’s displacement amplitude peak. These findings provide evidence that tympanal auditory recep- tors, comparable to the situation in mammals, comprise the required nonlinear response characteristics, which during two-tone stimulation lead to additional, highly localized deflections of the tympanum.

10aDPOAE10aInsect10alaser Doppler vibrometry10alocust10atympanum1 aMöckel, Doreen1 aNowotny, Manuela1 aKössl, Manfred uhttp://link.springer.com/10.1007/s00359-014-0914-201444nas a2200205 4500008004100000245006500041210006500106520072400171653002400895653002900919653001200948653002900960653001300989100001901002700002501021700002001046700002201066700001901088856013101107 2014 eng d00aEnergy localization and frequency analysis in the locust ear0 aEnergy localization and frequency analysis in the locust ear3 a

Animal ears are exquisitely adapted to capture sound energy and perform signal analysis. Studying the ear of the locust, we show how frequency signal analysis can be performed solely by using the structural features of the tympanum. Incident sound waves generate mechanical vibrational waves that travel across the tympanum. These waves shoal in a tsunami- like fashion, resulting in energy localization that focuses vibrations onto the mechanosensory neurons in a frequency-dependent manner. Using finite element analysis, we demonstrate that two mechanical properties of the locust tympanum, distributed thickness and tension, are necessary and sufficient to generate frequency-dependent energy localization.

10aenergy localization10afrequency discrimination10atension10atravelling flexural wave10atympanum1 aMalkin, Robert1 aMcDonagh, Thomas, R.1 aMhatre, Natasha1 aScott, Thomas, S.1 aRobert, Daniel uhttps://royalsocietypublishing.org/doi/10.1098/rsif.2013.0857https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2013.085702554nas a2200193 4500008004100000245007500041210006900116520185900185653001702044653004502061653001202106653002902118653001102147653001302158100001702171700002602188700002602214856012002240 2011 eng d00aNo evidence for DPOAEs in the mechanical motion of the locust tympanum0 aNo evidence for DPOAEs in the mechanical motion of the locust ty3 a

Distortion-product otoacoustic emissions (DPOAEs) are present in non-linear hearing organs, and for low-intensity sounds are a by-product of active processes. In vertebrate ears they are considered to be due to hair cell amplification of sound in the cochlea; however, certain animals lacking a cochlea and hair cells are also reported to be capable of DPOAEs. In the Insecta, DPOAEs have been recorded from the locust auditory organ. However, the site of generation of these DPOAEs and the physiological mechanisms causing their presence in the locust ear are not yet understood, despite there being a number of potential places in the tympanal organ that could be capable of generating DPOAEs. This study aimed to record locust tympanal membrane vibration using a laser Doppler vibrometer in order to identify a distinct place of DPOAE generation on the membrane. Two species of locust were investigated over a range of frequencies and levels of acoustic stimulus, mirroring earlier acoustic recording studies; however, the current experiments were carried out in an open acoustic system. The laser measurements did not find any evidence of mechanical motion on the tympanal membrane related to the expected DPOAE frequencies. The results of the current study therefore could not confirm the presence of DPOAEs in the locust ear through the mechanics of the tympanal membrane. Experiments were also carried out to test how membrane behaviour altered when the animals were in a state of hypoxia, as this was previously found to decrease DPOAE magnitude, suggesting a metabolic sensitivity. However, hypoxia did not have any significant effect on the membrane mechanics. The location of the mechanical generation of DPOAEs in the locust’s ear, and
therefore the basis for the related physiological mechanisms, thus remains unknown.

10abioacoustics10adistortion-product otoacoustic emissions10ahearing10alaser Doppler vibrometry10alocust10atympanum1 aMoir, H., M.1 aJackson, Joseph, Curt1 aWindmill, James, F.C. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.056465https://syndication.highwire.org/content/doi/10.1242/jeb.05646503077nas a2200265 4500008004100000245012200041210006900163520220600232653001302438653001202451653002102463653002602484653001502510653001902525653001602544653001202560653001302572100001802585700001502603700001302618700001602631700002502647700001902672856012002691 2013 eng d00aLow-pass filters and differential tympanal tuning in a paleotropical bushcricket with an unusually low frequency call0 aLowpass filters and differential tympanal tuning in a paleotropi3 a

Low-frequency sounds are advantageous for long-range acoustic signal transmission, but for small animals they constitute a challenge for signal detection and localization. The efficient detection of sound in insects is enhanced by mechanical resonance either in the tracheal or tympanal system before subsequent neuronal amplification. Making small structures resonant at low sound frequencies poses challenges for insects and has not been adequately studied. Similarly, detecting the direction of long-wavelength sound using interaural signal amplitude and/or phase differences is difficult for small animals. Pseudophylline bushcrickets predominantly call at high, often ultrasonic frequencies, but a few paleotropical species use lower frequencies. We investigated the mechanical frequency tuning of the tympana of one such species, Onomarchus uninotatus, a large bushcricket that produces a narrow bandwidth call at an unusually low carrier frequency of 3.2 kHz. Onomarchus uninotatus, like most bushcrickets, has two large tympanal membranes on each fore-tibia. We found that both these membranes vibrate like hinged flaps anchored at the dorsal wall and do not show higher modes of vibration in the frequency range investigated (1.5–20 kHz). The anterior tympanal membrane acts as a low-pass filter, attenuating sounds at frequencies above 3.5 kHz, in contrast to the high-pass filter characteristic of other bushcricket tympana. Responses to higher frequencies are partitioned to the posterior tympanal membrane, which shows maximal sensitivity at several broad frequency ranges, peaking at 3.1, 7.4 and 14.4 kHz. This partitioning between the two tympanal membranes constitutes an unusual feature of peripheral auditory processing in insects. The complex tracheal shape of O. uninotatus also deviates from the known tube or horn shapes associated with simple band-pass or high-pass amplification of tracheal input to the tympana. Interestingly, while the anterior tympanal membrane shows directional sensitivity at conspecific call frequencies, the posterior tympanal membrane is not directional at conspecific frequencies and instead shows directionality at higher frequencies.

10aauditory10akatydid10alaser vibrometry10aOnomarchus uninotatus10aOrthoptera10apseudophylline10atettigoniid10atrachea10atympanum1 aRajaraman, K.1 aMhatre, N.1 aJain, M.1 aPostles, M.1 aBalakrishnan, Rohini1 aRobert, Daniel uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.078352https://syndication.highwire.org/content/doi/10.1242/jeb.07835201942nas a2200205 4500008004100000245008000041210006900121520124300190653001701433653001201450653002901462653002101491653001401512653002101526653001301547100001401560700002701574700001501601856012001616 2008 eng d00aSexual dimorphism in auditory mechanics: tympanal vibrations of Cicada orni0 aSexual dimorphism in auditory mechanics tympanal vibrations of C3 a

In cicadas, the tympanum is anatomically intricate and employs complex vibrations as a mechanism for auditory frequency analysis. Using microscanning laser Doppler vibrometry, the tympanal mechanics of Cicada orni can be characterized in controlled acoustical conditions. The tympanum of C. orni moves following a simple drum-like motion, rather than the travelling wave found in a previous study of Cicadatra atra. There is a clear sexual dimorphism in the tympanal mechanics. The large male tympanum is unexpectedly insensitive to the dominant frequency of its own calling song, possibly a reflection of its dual purpose as a sound emitter and receiver. The small female tympanum appears to be mechanically sensitive to the dominant frequency of the male calling song and to high-frequency sound, a capacity never suspected before in these insects. This sexual dimorphism probably results from a set of selective pressures acting in divergent directions, which are linked to the different role of the sexes in sound reception and production. These discoveries serve to indicate that there is far more to be learnt about the development of the cicada ear, its biomechanics and evolution, and the cicada's acoustic behaviour.

10abiomechanics10ahearing10ahigh-frequency reception10alaser vibrometry10apredation10aselective forces10atympanum1 aSueur, J.1 aWindmill, James, F. C.1 aRobert, D. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.018804https://syndication.highwire.org/content/doi/10.1242/jeb.01880401726nas a2200193 4500008004100000245008300041210006900124520106900193653001201262653001701274653001101291653002901302653001201331653001301343100002701356700001401383700001501397856012001412 2009 eng d00aThe next step in cicada audition: measuring pico-mechanics in the cicada's ear0 anext step in cicada audition measuring picomechanics in the cica3 a

Female cicadas use sound when they select a mate from a chorus of singing males. The cicada has a tympanal ear; and the tympanal membrane, and constituent tympanal ridge, act as both acousto-mechanical transducers and frequency filters. The tympanal ridge is physically connected to a large number of mechanoreceptor neurons via a cuticular extension known as the tympanal apodeme. Using microscanning laser Doppler vibrometry, we measured for the first time the in vivo vibrations of the apodeme of female Cicadatra atra in response to the motion of the tympanum driven by sound. These measurements reveal that the nanoscale motion of the tympanal membrane is over a magnitude greater than that of the apodeme. Furthermore, the apodeme acts as an additional mechanical frequency filter, enhancing that of the tympanal ridge, narrowing the frequency band of vibration at the mechanoreceptor neurons to that of the male calling song. This study enhances our understanding of the mechanical link between the external ear of the cicada and its sensory cells.

10aapodeme10abiomechanics10aCicada10afrequency discrimination10ahearing10atympanum1 aWindmill, James, F. C.1 aSueur, J.1 aRobert, D. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.033019https://syndication.highwire.org/content/doi/10.1242/jeb.03301901954nas a2200193 4500008004100000245009700041210006900138520127800207653001701485653001101502653002901513653001201542653002001554653001301574100001801587700002601605700001901631856011001650 2006 eng d00aTuning the drum: the mechanical basis for frequency discrimination in a Mediterranean cicada0 aTuning the drum the mechanical basis for frequency discriminatio3 a

Cicadas are known to use sound to find a mate. While the mechanism employed by male cicadas to generate loud calling songs has been described in detail, little information exists to explain how their ears work. Using microscanning laser Doppler vibrometry, the tympanal vibrations in the cicada Cicadatra atra are measured in response to acoustic playbacks. The topographically accurate optical measurements reveal the vibrational behaviour of the anatomically complex tympanal membrane. Notably, the tympanal ridge, a distinct structural element of the tympanum that is a link to the receptor cells, undergoes mechanical vibrations reminiscent of a travelling wave. In effect, the frequency for which the maximum deflection amplitude is observed regularly decreases from the apex to the base of the ridge. It is also shown that whilst female ears are mechanically tuned to the male's song, the male's tympanum is only partially tuned to its own song. This study establishes the presence of a peripheral auditory mechanism that can potentially process auditory frequency analysis. In view of the importance of acoustic signalling in cicadas, this unconventional tympanal mechanism may be employed in the context of species recognition and sexual selection.

10abiomechanics10aCicada10afrequency discrimination10ahearing10atravelling wave10atympanum1 aSueur, Jerome1 aWindmill, James, F.C.1 aRobert, Daniel uhttps://bio.acousti.ca/content/tuning-drum-mechanical-basis-frequency-discrimination-mediterranean-cicada