. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. B. p^t) Flexible hinge F2(t) IRdl ]— Fulcrum mode 1. Figure 4. The anatomy of mechanical coupling, and vibrational modes of the flexible intertympanal bridge. (A) Close-up of the intertympanal bridge connecting the tympanal membranes. (B) Simple mechanical model of the bridge as a seesaw endowed with two rigid bars connected by a flexible central hinge ( = ). (C) On the basis of the laser vibrometric micromechanical analysis, it is suggested that two basic modes can char- acterize the observed mechanical response. Bending oc
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. B. p^t) Flexible hinge F2(t) IRdl ]— Fulcrum mode 1. Figure 4. The anatomy of mechanical coupling, and vibrational modes of the flexible intertympanal bridge. (A) Close-up of the intertympanal bridge connecting the tympanal membranes. (B) Simple mechanical model of the bridge as a seesaw endowed with two rigid bars connected by a flexible central hinge ( = ). (C) On the basis of the laser vibrometric micromechanical analysis, it is suggested that two basic modes can char- acterize the observed mechanical response. Bending occurred at low fre- quencies (mode 1; <4 kHz), whereas rocking was measured at intermedi- ate frequencies (mode 2: 5-1 kHz). At higher frequencies (\5 kHz and above), bending and rocking modes combine to elicit motion in one tympanum only (mode 1 + 2). a human hair, and observing the other deflect upwards as a result. Deflection shapes obtained by microscanning laser Dopp- ler vibrometry for different stimulus frequencies (, 2, 5 or 15 kHz) reveal that this micromechanical system can produce several different patterns of deflection that are reminiscent of the movements of a flexible seesaw (Fig. 4B). The simple mechanical model shown in Figure 4B has been proposed as a reasonable functional, and intuitively accessible, approximation of this unconventional peripheral auditory system (Miles et al, 1995: Robert et al. 1996). The physical action of the intertympanal bridge is to convert small acoustic ITDs into larger time and amplitude differ- ences at the mechanical level. The functional principle for this effect resides in the somewhat complex linear interac- tion between two coupled oscillators—the tympanal mem- branes. Very briefly, for low frequencies of stimulation (2 kHz), the deflections of the ipsilateral and contralateral membranes show little difference in amplitude and phase. In this case, the forces applied to the bridge (Fig. 4B) have a phase difference of
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
