New Data on the Motion of the Normal and Reconstructed Tympanic Membrane

Abstract

Hypothesis The sound-induced motion of the tympanic membrane has features that are most consistent with modal responses to a uniform stimulus. Background Conceptual models of the coupling of tympanic-membrane motion to the ossicular chain can be classified as either modal responses to a uniform stimulation of the entire membrane, or traveling wave models in which sound energy is captured at the membrane’s rim and travels along the surface to the umbo. The stroboscopic holography technique we employ can separate strongly modal or traveling-wave dominated motions of the tympanic membrane surface. Methods We use computer-aided opto-electronic holography with stroboscopic illumination to measure the magnitude and phase of the sound-induced motion of over 40000 points on the surface of the tympanic membrane in cadaveric human temporal bones. Our techniques are sensitive to motions of the membrane as small as 0.01 microns, and allow determinations of membrane displacement at frequencies as large as 20 kHz. Results We report clear signs of both modal tympanic membrane responses and traveling waves on the human tympanic membrane. Modal responses are seen throughout the frequency range, while the traveling waves are most apparent between 2 and 8 kHz. In general, the magnitudes of the traveling waves are small compared to the modal magnitudes. Conclusion Much of the motion of the tympanic membrane is well approximated by modal motions of the TM surface. This conclusion has implications for ear drum pathology and its treatment.

Human middle-ear model with compound eardrum and airway branching in mastoid air cells

“…Spatial integration of forward sound power over the eardrum in the present two-component model comes from the fact that the acoustic pressure acts over the entire surface of the eardrum via its propagating and evanescent modes. The appearance of eardrum modal resonances at high frequencies in the present model is qualitatively consistent with experimental findings of multiple resonant modes of vibration of the tympanic membrane at frequencies above 8 kHz up to as high as 18 or 20 kHz (Rosowski et al, 2011;Cheng et al, 2010). These findings suggest independent motions of the manubrium relative to the remainder of the tympanic membrane.…”

Wave motion on the surface of the human tympanic membrane: Holographic measurement and modeling analysis

“…The traveling-wave-like motion could also be attributed to damped modal motion. These data were used to test various models and interpretations of TM motion in the literature, and were found to be consistent with the interpretation of de La Rochefoucauld and and others (Cheng et al, 2010;Rosowski et al, 2011). The contribution of these different motion patterns to ME function is a point of continuing study.…”

“…Our previous studies have shown that sound-induced motions of the mammalian TM follow different patterns (simple, complex, ordered) within different stimulus frequency ranges . We have also suggested that the complex and ordered patterns result from the interaction of modal motions and traveling waves on the TM surface (Cheng et al, 2010;Rosowski et al, 2011). However, the magnitudes and wave numbers of the different modes of motion have not yet been quantified and questions, such as how modal motions and putative surface waves traveling on the TM surface are related to ME sound transmission, remain unanswered and need further investigation.…”

Panel 2: Anatomy (Eustachian Tube, Middle Ear, and Mastoid—Anatomy, Physiology, Pathophysiology, and Pathogenesis)

“…Recent studies by Rosowski et al reported clear signs of both modal TM responses and traveling waves on the human TM. 81,82 Characterization of the viscoelastic and dynamic properties [83][84][85][86] and 3D displacement patterns of the TM 87,88 to different sound frequencies is the first step to develop new anatomically accurate FE models, which could facilitate a better understanding of the complicated mechanics of sound reception by the ear. Surface measurement methods, such as laser Doppler vibrometry (LDV) and optoelectronic holography, provide quantitative information about the amplitude and phase of TM vibrations.…”