1,917 research outputs found
Data supporting Lung-to-ear sound transmission does not improve directional hearing in green treefrogs (Hyla cinerea)
No full textThe 11 data files in this archive accompany the publication: Christensen-Dalsgaard J, Lee N, Bee MA (in press) Lung-to-ear sound transmission does not improve directional hearing in green treefrogs (Hyla cinerea). Journal of Experimental Biology.Amphibians are unique among extant vertebrates in having middle ear cavities that are internally coupled to each other and to the lungs. In frogs, the lung-to-ear sound transmission pathway can influence the tympanum’s inherent directionality, but what role such effects might play in directional hearing remain unclear. In this study of the American green treefrog (Hyla cinerea), we tested the hypothesis that the lung-to-ear sound transmission pathway functions to improve directional hearing, particularly in the context of intraspecific sexual communication. Using laser vibrometry, we measured the tympanum’s vibration amplitude in females in response to a frequency modulated sweep presented from 12 sound incidence angles in azimuth. Tympanum directionality was determined across three states of lung inflation (inflated, deflated, reinflated) both for a single tympanum in the form of the vibration amplitude difference (VAD) and for binaural comparisons in the form of the interaural vibration amplitude difference (IVAD). The state of lung inflation had negligible effects (typically less than 0.5 dB) on both VADs and IVADs at frequencies emphasized in the advertisement calls produced by conspecific males (834 Hz and 2730 Hz). Directionality at the peak resonance frequency of the lungs (1558 Hz) was improved by ≅ 3 dB for a single tympanum when the lungs were inflated versus deflated, but IVADs were not impacted by the state of lung inflation. Based on these results, we reject the hypothesis that the lung-to-ear sound transmission pathway functions to improve directional hearing in frogs.National Science FoundationChristensen-Dalsgaard, Jakob; Lee, Norman; Bee, Mark A. (2020). Data supporting Lung-to-ear sound transmission does not improve directional hearing in green treefrogs (Hyla cinerea). Retrieved from the University Digital Conservancy, https://doi.org/10.13020/rj08-sc66
Wave Leakage in a Magnetized Isothermal Atmosphere
No full text. The present investigation is a continuation of earlier work by Hasan & Christensen-Dalsgaard (1992) and Banerjee, Hasan & Christensen-Dalsgaard (1995), where the interaction of various elementary modes in a stratified atmosphere with a vertical magnetic field was studied. In the present study, we concentrate on the behaviour of the modes near the avoided crossings in the the k \Gamma ! diagram for zero-gradient boundary conditions. We find that in such regions the frequencies of the modes become complex, whereas away from the avoided crossings the frequencies are real (in the adiabatic case) for these boundary conditions. Strong mode coupling in the avoided-crossing regions permits energy leakage for zero-gradient boundary conditions. Key words: MHD - Sun: oscillations - Sun: magnetic fields 1. Introduction Study of wave motions can reveal useful information on the structure of magnetic elements and thus serve as a powerful diagnostic tool. Observations of oscillations in the solar ..
Biophysics, neural processing and robotics of the lizard ear, a highly directional sensor
No full textThe ear of lizards shows strongly directional responses with up to 40 dB differencesinsensitivitytoipsi-andcontralateralstimulation.Thedirectionality is generated by a simple principle: strong acoustical coupling of the eardrums through the large mouth cavity. Our laser vibrometry measurements show that the lizard ear is a two-input system with approximately 0 dB contralateral transmission gain in a 2 kHz frequency band. This transmission is boosted by resonances in the large, open tympanic cavities. Probably because of these resonances, the interaural delay is approximately three times larger than the arrival-time differences at the lizard eardrums. Since already the ear is directional, the subsequent neural processing may be much simpler than in mammals, for example, where directionality is based on neural computation. Our neurophysiological experiments show that binaural comparison is based on contralateral inhibition with no apparent segregation of time and intensity processing. This simple computation generates a strongly directional lateralization that is suf cient to orient the animal. This has been shown by robot simulations, where the ear is modelled by a simple three- impedance acoustical analog. Implementation of the model in a digital signal processor and subsequent neural processing based on binaural comparison produces a robust directional response
Biophysics, neural processing and robotics of the lizard ear, a highly directional sensor
No full textThe ear of lizards shows strongly directional responses with up to 40 dB differencesinsensitivitytoipsi-andcontralateralstimulation.Thedirectionality is generated by a simple principle: strong acoustical coupling of the eardrums through the large mouth cavity. Our laser vibrometry measurements show that the lizard ear is a two-input system with approximately 0 dB contralateral transmission gain in a 2 kHz frequency band. This transmission is boosted by resonances in the large, open tympanic cavities. Probably because of these resonances, the interaural delay is approximately three times larger than the arrival-time differences at the lizard eardrums. Since already the ear is directional, the subsequent neural processing may be much simpler than in mammals, for example, where directionality is based on neural computation. Our neurophysiological experiments show that binaural comparison is based on contralateral inhibition with no apparent segregation of time and intensity processing. This simple computation generates a strongly directional lateralization that is suf cient to orient the animal. This has been shown by robot simulations, where the ear is modelled by a simple three- impedance acoustical analog. Implementation of the model in a digital signal processor and subsequent neural processing based on binaural comparison produces a robust directional response
Biophysics, neural processing and robotics of the lizard ear, a highly directional sensor
No full textThe ear of lizards shows strongly directional responses with up to 40 dB differencesinsensitivitytoipsi-andcontralateralstimulation.Thedirectionality is generated by a simple principle: strong acoustical coupling of the eardrums through the large mouth cavity. Our laser vibrometry measurements show that the lizard ear is a two-input system with approximately 0 dB contralateral transmission gain in a 2 kHz frequency band. This transmission is boosted by resonances in the large, open tympanic cavities. Probably because of these resonances, the interaural delay is approximately three times larger than the arrival-time differences at the lizard eardrums. Since already the ear is directional, the subsequent neural processing may be much simpler than in mammals, for example, where directionality is based on neural computation. Our neurophysiological experiments show that binaural comparison is based on contralateral inhibition with no apparent segregation of time and intensity processing. This simple computation generates a strongly directional lateralization that is suf cient to orient the animal. This has been shown by robot simulations, where the ear is modelled by a simple three- impedance acoustical analog. Implementation of the model in a digital signal processor and subsequent neural processing based on binaural comparison produces a robust directional response
Lecture Notes on Stellar Oscillations
No full textt. Further comments and corrections are most welcome. Preface to 3rd edition The notes have been very substantially revised and extended in this edition, relative to the previous two editions. Thus Chapters 6 and 9 are essentially new, as are sections 2.4, the present section 5.1, section 5.3.2, section 5.5 and section 7.6. Some of this material has been adopted from various reviews, particularly Christensen-Dalsgaard & Berthomieu (1991). Also, the equation numbering has been revised. It is quite plausible that additional errors have crept in during this revision; as always, I should be most grateful to be told about them. Preface to 4th edition In this edition three appendices have been added, including a fairly extensive set of student problems in Appendix C. Furthermore, Chapter 10, on the excitation of oscillations, is new. The remaining revisions are relatively minor, although new material and updated results have been added throughout. The pre
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